2nd gear slip after service

[Mounce]

So, I did the DIY flush recently as some of you saw I posted. Same day, in town, I noticed a 2-3 shift flair which had been narrowed down to 2nd gear slipping under power. It's not the whole gear and it doesn't always happen. I only notice it when trans temps are above 180 like on a hot summer day in Alabama in traffic around town. Fluid is a little over full when 180+, I haven't corrected it yet but I really don't think that's the problem to begin with.

I've mostly learned to drive around it and don't push 2nd hard as I used to. It made a 400 mile interstate trip fine and I've driven around here with no issues and I'm positive it'll make it back home 400 miles tomorrow.

However I'm going to need to address this before it burns up. I'm wondering if the shift kit by ctpowetrain on ebay will fix this? I know lots have experience with the kit here. It's like 2nd just isn't holding tight enough or the clutches are worn, I'm not sure. Just saddened that I serviced it and revealed a problem at such a bad time.

I'm stuck between tossing the kit in it or just babying it till it dies and throwing a reman in.

Side note, this is on my 2003 Silverado, 137,000 miles. 4l60e of course.

 

[littleblazer]

Literally sounds like what the escalade did, and yes the CT power train kit worked. Shifts better than new now with the pwm delete.

Don't watch the whole thing. Don't watch anything except around the 40 second mark where it flairs on the 2nd gear shift. Trust me, save your time, just read the instructions.

 

[Reprise]

Since it only happens above 180F -- if you don't already have an aux trans cooler installed, might be worth it to put one in. Maybe one on the larger side - 20-30K BTU. Stacked plate or at least a tube / plate. The tube / fin are the cheapest, but also the least efficient.

My tiny 10K stacked plate in the Envoy handles all the trans cooling (bypass), and keeps things about 165F or so, burbs or highway, except when it's above 95F, or I'm towing heavy (which I don't do with the Voy any more, anyway)

In fact, as I think about it... I might even do this before putting in the shift kit fixes -- cheaper and easier. If you decide to put in the CT Performance kit later, the cooler won't be wasted.

No worries on the fluid level, and it'll get 'adjusted', anyway, as you do your work.

 

[Mounce]

Would a cooler help? Yeah, bandaid the current issue. I'm not for bandaids on my DD.

I appreciate the input, luckily gm gave the full size trucks a factory towing package with external + internal trans coolers. I'm not worried about the temps at all, it's well regulated. 180 and all only comes in traffic and hot cycles during 100 degree days. Getting a little warm shouldn't cause these issues on a healthy trans. I've got something going out since I've changed the fluid, the heat cycles have always been present. Trans was rock solid before the service, idk if I flushed some sludge loose or what but I had zero issues prior to service. Pan wasn't too dirty, trailblazer had way more clutch material in the pan than the Silverado. I'm honestly shocked with this outcome lol.

 

[Mooseman]

It's been mentioned by some that if the trans is on its way out it may exhibit some slip with the loss of the suspended clutch material grit after a fluid replacement.

The PCM/TCM also has a fluid pressure setting that adjusts itself as the trans ages that can be reset with a Tech 2. I know that when a PCM/TCM is tuned for firmer shifts, the pressure is increased in the tune. Basically does the same as the shift kit. The shift kit however does it a bit more aggressively.

If you leave it as-is, I'd just monitor it to see if it gets worse. A shift kit may correct it.

 

[Reprise]

So, I did the DIY flush recently as some of you saw I posted.

I found your post. Just curious. Did you do this all by yourself? I've been wanting to do it to my Sierra (4L80), but worried I'd goof up the timing between pumping / filling / cycling the motor off & on, & wind up burning up the trans as a result (I trashed the 4L60 in my Envoy due to lack of fluid, although not as part of a 'flush').

So I was just going to do a regular pan drop / filter change, to be 'safe'.

 

[Mooseman]

There are no worries as the trans is not doing anything except pumping fluid. Nothing is engaged or shifting and the gerotor pump is not affected by a momentary loss of fluid. I've done it several times including on the 6L80E with no issues. Even when I did it on my 02 when I first got it with brown fluid, the trans lasted another 100k km.

 

[Mounce]

Yeah done myself, just get you a hose long enough to reach a bucket within eyesight while you're within reach of the key. As soon as it sputters turn it off and refill. I had a helper on the TB when I done it the first time but solo'd the Silverado and actually never let it run completely dry, just waited till I noticed the flow change and a little cough of fluid then cut her off.

MAY03LT has a video on YouTube on an Envoy and another on a Tahoe. They're all the same. Plus a few how-to's around here if you search.

 

[littleblazer]

So where is your mind at right now? 137k is awfully low mileage to have an issue like this....

 

[Sparky]

Depends on how it was previously treated too, workload, and age. Earlier 4L60E were more prone to issues in general.

I'd do the ctpowertrain kit. Heck I do that kit to every 4L60E I get regardless of whether it is exhibiting symptoms or not as preventive care. 215k on the TB before rust killed it, Silverado has 213k and counting, trans in the Camaro has 170k ish on it and it was all symptomatic before the kit install something like 10-11 years ago now (crazy to think about).

 

[Mektek]

Try an additive. I used TransMedic on a 4t60e that was hard shifting into each gear. After less than 100 mi. it returned to normal and no other fix was required.
After two years the problem returned. I did the diy flush with pennzoil high mileage dex 6 fluid. Shifting returned to normal soon after. I recommend the pennzoil synthetic fluid- it really made a difference for me and was only slightly more expensive then regular dex 3.

 

[gmcman]

@Mounce I had a 2-3 flare around 160K, I changed my separator plate which had a check ball push through the plate. Along with the accumulator pistons and vette servo.

How many miles was on that fluid?

I'm off to work but will look for that thread.

I would use the truck sparingly as this is how your band gets smoked if not careful.

 

[littleblazer]

Depends on how it was previously treated too, workload, and age. Earlier 4L60E were more prone to issues in general.

I'd do the ctpowertrain kit. Heck I do that kit to every 4L60E I get regardless of whether it is exhibiting symptoms or not as preventive care. 215k on the TB before rust killed it, Silverado has 213k and counting, trans in the Camaro has 170k ish on it and it was all symptomatic before the kit install something like 10-11 years ago now (crazy to think about).

I mean ours made it 200k behind a 6.0l before it even started. Then another 70k before I put in the shift kit. And now it's like new again. I expect the motor to let loose around 350k.

 

[Mounce]

Depends on how it was previously treated too, workload, and age. Earlier 4L60E were more prone to issues in general.

I'd do the ctpowertrain kit. Heck I do that kit to every 4L60E I get regardless of whether it is exhibiting symptoms or not as preventive care. 215k on the TB before rust killed it, Silverado has 213k and counting, trans in the Camaro has 170k ish on it and it was all symptomatic before the kit install something like 10-11 years ago now (crazy to think about).

Symptomatic? Curious what your symptoms were.

Try an additive. I used TransMedic on a 4t60e that was hard shifting into each gear. After less than 100 mi. it returned to normal and no other fix was required.
After two years the problem returned. I did the diy flush with pennzoil high mileage dex 6 fluid. Shifting returned to normal soon after. I recommend the pennzoil synthetic fluid- it really made a difference for me and was only slightly more expensive then regular dex 3.

I appreciate the input, I had highly considered an additive but that's just a bandaid. I used a name brand widely popular fluid that 80% of everyone else uses without issue so I'm not worried about fluid quality issues, and it's a dex6 fluid which is the recommended refill on these. I'm feeling this is a mechanical issue that I inadvertently exposed. She's had some hot suppers in my ownership.

@Mounce I had a 2-3 flare around 160K, I changed my separator plate which had a check ball push through the plate. Along with the accumulator pistons and vette servo.

How many miles was on that fluid?

I'm off to work but will look for that thread.

I would use the truck sparingly as this is how your band gets smoked if not careful.

136,000 and some change on the fluid as far as I know, not original owner and I've only had it for 30k of its life. T'was quite nasty though. I was thinking it could be a ball seat issue or some other moving/sealing part, one of the common issues like you mention. I guess it was varnished and the new fluid washed out the junk and exposed the leak. That's all I can rationalize with this. I wish I could park it till fixed but I've got work all week and my fall back is the TB which is mom's car and I can't take it the whole week.. Plus it's got issues I need to get to as well so I'd rather it take the rest. Unfortunately I'm prepared to slap a trans in my truck if needed, I'd rather not but I'll bite that bullet if/when it comes.

At this point I'm planning on buying the kit and starting on it Saturday night or Sunday. My cheapest easiest option at this point.

 

[Mounce]

Just wanna verify the only difference between these two kits is the first includes the corvette servo and is the one everyone uses.. Looks like it also has the manual and the other doesn't.

4L60E 4L65E 1996-2006 1870 P1870 Code Buster Combo Kit Corvette Servo ATSG Book | eBay

4L60E 1870 P1870 "Code Buster" Combo Kit 1996 To 2006. This Kit Will Solve And Cure The P1870 TCC Fault Code On Gm 4L60E Automatic Transmissions. P1870 CODE. NEW ATSG BLUE TECH MANUAL. 4L60E / 4L65E Pinless accumulator piston.

rover.ebay.com

And this second one has everything but the corvette servo, correct?

4L60E 4L65E 1996-2006 1870 P1870 Code Buster Update Kit With TransGo SK4L60E New | eBay

TRANSGO SK4L60E SHIFT KIT This Kit Will Solve And Cure The P1870 TCC Fault Code On GM 4L60E Series Automatic Transmissions. P1870 CODE. 4L60E 4L65E "1870 Code-Buster Kit" 1996 Thru 2006 Only! NEW 4L60E TRANSGO UPDATED VALVE BODY SEPARATOR PLATE.

rover.ebay.com

Also, I don't see where these kits include check balls. I've seen some recommend replacing them and others say it's unneeded. What's the general verdict?

Anything else I should do while inside? I figure I'll put a new filter in again, might as well as I'll need a new pan gasket I figure.

 

[littleblazer]

Just wanna verify the only difference between these two kits is the first includes the corvette servo and is the one everyone uses.. Looks like it also has the manual and the other doesn't.

4L60E 4L65E 1996-2006 1870 P1870 Code Buster Combo Kit Corvette Servo ATSG Book | eBay

4L60E 1870 P1870 "Code Buster" Combo Kit 1996 To 2006. This Kit Will Solve And Cure The P1870 TCC Fault Code On Gm 4L60E Automatic Transmissions. P1870 CODE. NEW ATSG BLUE TECH MANUAL. 4L60E / 4L65E Pinless accumulator piston.

rover.ebay.com

And this second one has everything but the corvette servo, correct?

4L60E 4L65E 1996-2006 1870 P1870 Code Buster Update Kit With TransGo SK4L60E New | eBay

TRANSGO SK4L60E SHIFT KIT This Kit Will Solve And Cure The P1870 TCC Fault Code On GM 4L60E Series Automatic Transmissions. P1870 CODE. 4L60E 4L65E "1870 Code-Buster Kit" 1996 Thru 2006 Only! NEW 4L60E TRANSGO UPDATED VALVE BODY SEPARATOR PLATE.

rover.ebay.com

Also, I don't see where these kits include check balls. I've seen some recommend replacing them and others say it's unneeded. What's the general verdict?

Anything else I should do while inside? I figure I'll put a new filter in again, might as well as I'll need a new pan gasket I figure.

The transgo box includes the check balls. I thin you need to reuse some and replace others... I didn't use the manual when I did mine (its straight forward and the transgo instructions are pretty clear). Otherwise identical. Make sure you reuse the stock accumulator springs when you use the new pistons. The transgo ones are too short for the pinless ones. You get about 1/4 of the actual accumulation. You can tell which one it is because the replacement spring is much shorter.

They talk about it here. The HD2 kit is a bit different but the springs are the same height.

As for anything else... don't drop your valve body and you shouldn't have to replace solenoids like I did lol.

 

[mrrsm]

Here is some additional On Topic information from the Sonnax People suggesting the use of an Amp Draw Test on the 4L60E 12 Volt Positive using the DVOM Leads to replace the Power Fuse Location. With the typical DVOM placed on the AMPS setting (... or when using a Small Amp Clamp) you can measure the Amp Draw and Duration while employing your Tech 2 to command the "A" and "B" Shift Solenoids On and Off.

If you can reproduce similar Test Results as described below... then perhaps a PCM Re-Flash would help here... before condemning the PCM entirely:

4L60E Flares on 2-3 Shift? Could be a bad computer | Sonnax

4L60-E 2-3 flares are usually centered on problems inside the transmission. See an example of how to use amperage draw testing to uncover another possible cause...

www.sonnax.com

 

[Sparky]

Symptomatic? Curious what your symptoms were.

Lack of TCC lockup when warm (that went on for a long while), then slamming the 1-2 shift so hard it would feel like I got rear ended, delayed shifting of 1-2. I know other symptoms that the kit deals with is shift flares, poor hold, etc.

I always have reused the check balls, but the new separator plate is good. Some issues can definitely be caused by a worn plate.

I get the kit with the vette servo because you have to get in there anyway to complete the kit install, which involves almost manging the O ring if you're not careful, so might as well get the new servo and O ring IMO and not worry about destroying the old one.

 

[Mounce]

What's the 5/32 drill bit in the kit for? I haven't seen it mentioned anywhere and I've looked through the instructions a couple times now.

 

[littleblazer]

What's the 5/32 drill bit in the kit for? I haven't seen it mentioned anywhere and I've looked through the instructions a couple times now.

It was for one of the holes on the separator plate iirc. I just used my index. You did the one that came with a new plate no? One hole had a range for desired feeling I think...

 

[Mounce]

Yeah new plate, enlarged all to .093 that specified. Some said .073-.086 but that's smaller than the .093 am I right? I'm not fluent with my thousandth decimals vs actual size but that's my understanding that a .073 is smaller than a .093.

Plus the drill bits were labeled one 5/32 and one .093 why not keep it all fractions or decimals?? Lol I skimmed everything a couple times and never saw 5/32 anywhere.

 

[Reprise]

See pg 6 (inset) of the instructions for the use of the 5/32 bit. It's optional, for installation of a roll pin to make it easier to swap springs, etc., in the VB.

PS: Yes, you're correct on decimal sizing -- the larger the leftmost number, with fewest zeros in front, the larger the value. Any number '1' or larger to the left of the decimal is larger still.

 

[Mounce]

See pg 6 (inset) of the instructions for the use of the 5/32 bit. It's optional, for installation of a roll pin to make it easier to swap springs, etc., in the VB.

PS: Yes, you're correct on decimal sizing -- the larger the leftmost number, with fewest zeros in front, the larger the value. Any number '1' or larger to the left of the decimal is larger still.

Wow it's all too obvious now. Thanks!

 

[littleblazer]

I forgot all about that pin. Mainly because I didn't use it lol. That makes more sense though.

 

[Reprise]

Well, I had to look it up; no way I'd remember that! It also explains (IMO) why they went with a fractional bit for that one.

And I didn't install that pin, either.

 

[Mounce]

I opted to put the pin in. They made it sound like a good deal lol.

So, everything seems to work well so far, took it on a 15 mile shakedown. 1-2 shift is pretty hard. Harder than before, not sure I like that. Everything else seems fine and "5th gear" solid tcc lockup is great. Had to drop the trans cross member partially to do the servo, took three of the four bolts out and hinged it down on the last one. Separator plate was surprisingly only minorly hammered, however one was seating off centered and had egged the hole a bit.

Took me many more hours than I'll mention. Approximately 2.5 hours of that was looking for a bolt that I lost and going to Lowes to pick up the closest equivalent which was 3-4 mm too long. Spent a while trying to shorten one to make it work, went through three out of the four in the pack before using a washer hit me. Grinding them down and trying to chamfer the thread start ruined the starting threads everytime.

So got the bolt and washer in, went to dump the rest of the fluid from the pan into a jug to prevent a spill during reassembly and hello, my bolt was hidden under the fluid. I had dropped a bolt during my struggles of refitting the valve body and I thought that one had went missing because I didn't remember picking it up. Instead I apparently dropped a bolt during disassembly into the pan. I threatened looking in the pan during my searches but I had set it on a stool to keep it away from dust being kicked up when walking around and I knew that I didn't put a bolt in there and there was no way that a dropped bolt could jump up 2 feet into a pan. What a dope lol. Found it by luck. I highly considered not dumping that fluid.

So, to follow up, I wouldn't have put the vette servo in had I known 1-2 would be so harsh now, maybe I'll start to like it over time. Also, simple idea, but keep up with every single bolt, dummiehead. And the shift detent spring lever? Take it off, assembly will go much smoother. Was confident that it wouldn't affect assembly, was also dead wrong.

 

[Reprise]

Good job. Don't worry about time taken. Better to err on side of caution.

The 1-2 should get a little better once the fluid comes up to temp & line pressure lowers a bit. My 1-2 has always been firm, even before the kit / servo. The good thing is, you can remove the servo, if you want (drain fluid first)

 

[littleblazer]

Question, you disconnect the battery when you did it? I didn't on mine but instead pulled the starter relay and fuel pump relay... as it turned out letting the ecm sit cleared the short term line pressure adjustments and the shifts were softer. Just an idea.

What springs you use for the accumulators?

I'm glad it seems to have worked! Howd the fluid look when it came out?

 

[Sparky]

It should smooth some. Only time my truck hits 1-2 hard is under heavier throttle.

 

[Mooseman]

When I did my 02, the 1-2 shift was very harsh and never got better. I think I buggered up on drilling out one of the holes. And I didn't use the Vette servo neither.

In my 07, I have the PWM tuned out so that won't be an issue down the road. Not sure if I'll ever do a shift kit again because that 1-2 shift was really bad. YMMV.

 

[Reprise]

When I did my 02, the 1-2 shift was very harsh and never got better. I think I buggered up on drilling out one of the holes. And I didn't use the Vette servo neither.

Funny you mention this - the guy who rebuilt my trans said I drilled out 'the wrong hole'. Given what you know of me, do you think I didn't follow the instructions? LOL

While my 1-2 was always harsh firm, at least it didn't get worse, between the drilled plate & servo (the builder put it in; like you, I skipped it when I put my kit in)

One thing I will say... it has never slammed the 1-2 again after the kit / rebuild / cooler, even when I had the trans up to nearly 240F once, while towing.

When I first got the Envoy, the coolant probably hit close to 220F in stop/slow on fresh asphalt / hot summer day, and as Sparky mentioned, it felt like someone rear-ended me when that shift hit. I actually turned off the A/C and flipped on the heater to cool things down. A miserable trip.

 

[Mounce]

Question, you disconnect the battery when you did it? I didn't on mine but instead pulled the starter relay and fuel pump relay... as it turned out letting the ecm sit cleared the short term line pressure adjustments and the shifts were softer. Just an idea.

What springs you use for the accumulators?

I'm glad it seems to have worked! Howd the fluid look when it came out?

I did not disconnect the battery. That's an idea though, I might clear it (restart the adaption table or whatever) at work with the scanner if it doesn't chill and it's compatible.

I used the springs that the transgo kit called for. I remembered you saying that they were wrong, compared them to stock and the new springs were shorter than the old, however the pistons had the same general dimensions so they were gonna be shorter no matter if I used the stock pistons like transgo thought you would or if you swapped to pinless.

Fluid was decent, kinda dark but that's just where it washed the trans out, everything steel in there had a nice coat of something dark which I assume is clutch material. I'm not worried about it, it had some in the pan, lots in the pan when I first serviced it before issues. And as a comparison the TB had twice the amount of this material in the pan when I serviced it a couple years ago at a lower mileage.

So, everyone else ended up with three springs on their vette servo under the retainer plate right? That's the only question I have as I can't remember if the transgo instructions had the servo swap in mind or if the recommended spring combo is good in any servo, or if the combo is catered to a stock servo. This 1-2 is killer, like pretty sure I heard it chirping tires on wet road. Bucks the truck hard. It's nice 1/4 throttle or under, real nice and crisp. 1/3 and above? Hold on boys! Even WOT. Like anything above 1/3 throttle under load makes it bang.

 

[Reprise]

The TransGo instructions give a procedure for modifying your existing OEM servo housing; they're not assuming you're swapping the servo outright. The Vette servo is a time-honored (& cheap) mod that the F-body people, etc., used. It gets thrown in the kit by the vendor; not a TransGo part. IIRC, TransGo doesn't even include a new o-ring for the servo (tho they do assume you'll be modding the servo, per their instructions.)

With mine, my mech growled (after the fact, of course) that I didn't 'need' the Vette servo. I explained that it came with the kit (and that if he had recommended it not be put in, I'd have gladly told him to skip it.) Then I had to explain 'the kit' to him... LOL.

One of these days, I need to get under the Envoy and see if the guy who built it even *put in* the servo, given what you describe it feels like under medium / WOT. Not that I stand on the pedal very much, especially from a standing start.

 

[littleblazer]

Resetting the tables will accomplish the same thing and definitely helped because it dropped like pressure. As far as it being firm, ye it is but not brutal from what I feel... but with 300k or so on the thing I don't exactly push the truck either...

For the springs, it was mainly that the pinless accumulator has the deeper pocket so when installed part of the spring was shrouded... I had spoken with the company that made the pinless accumulator and they suggested their own springs or reusing stock because of that. When I tested it with the transgo springs there was hardly any accumulation on mine however being as there are different positions in all 4l60s it's possible yours was the style where it was more like the pinless model.

 

[Mounce]

So, very very slight improvement with adapted pressure reset but still, anything above 2k and she bites. Confirmed today that it spins the shift on wet roads under moderate throttle lol.

Between all of the cells on the table the highest was 72.4kpa and lowest was 5.17kpa of adaption. I thought that every shift had adaptions but it only showed 1-2.

What would cause this adverse reaction in the shift becoming harder after the kit? Accumulator spring too small? These bits and pieces are some that I don't have a firm knowledge on but from what I read the accumulators dampen the pressure spike during a shift? And the servo just controls engaging the band?

I'm trying to see what I need to do to correct this if/when I decide to. Call/lookup up sonnax and get their recommended springs for these accumulators? Honestly at this point I'm kinda getting used to it, but it still feels like it's going to break something eventually.

Observations over the week since kit:

1-2 is hard. Quick.
2-3 is meh, seems the same. Soft and smooth.
3-4 is quick and firm.
TCC lock is nice.

Haven't been able to recreate my 2nd gear issue yet. However it's cooled off and trans temp hasn't gotten above 165 since but I feel confident that it's cured.

 

[Reprise]

(you may find this useful, from Sonnax's site: )

Transmission Hydraulics: Accumulators & Shift Feel | Sonnax

The role of transmission accumulators of controlling shift feel is evolving. Here's what's changed and what might be coming down the road. Learn more today!

www.sonnax.com

You're basically correct about the function of the accumulators / servo. They do complement each other, and if I understood how you installed the kit, you did all the steps that would increase firmness on those components (swap / add accumulator springs, servo replacement, enlarged (drilled) orifice in separator plate)

So... for you... "how to get the 1-2 a little softer?"

I'd swap the servo back to the OEM (whether or not you modify the housing, as per the TransGo instructions, is up to you. If you do modify it, it will firm it back up -- not as much as the Vette servo, but something in-between.) That's also a one-way operation -- if you grind the relief notches in the piston housing (see page: '2nd piston upgrades') and don't like it afterward, you have to get new parts (they're available, of course, but it's a pain to keep swapping things in / out, right?) But the servo will have the greatest effect on the shift firmness, IMO. I'd guess that the other two things would have about an equal effect, comparing them to one another (but each of them much less than the servo.)

For the separator plate... if you replace it with a stock OEM plate, I'd get a set of the Torlon checkballs (got mine cheap on eBay), so that the 1-2 checkball doesn't eventually hammer through the stock plate.

It's been awhile since I installed my kit, but IIRC, there were only one or two holes I had to (chose to) drill in the plate, as the others were already widened to the revised spec of the kit instructions. But one of them is for the 1-2 shift, so if you did drill it (.093) and want to keep the hardened plate, you'll need to get a second one (they're available separately, along with new gaskets -- make sure you get the right ones for your MY).

Finally, the accumulator pistons / springs. If you wanted to put the stockers back in, just make sure that you get a replacement for any that are plastic (on mine, only the 4th accumulator was plastic; the forward & 2nd were metal). Also, make sure there's no elongation of the pin bore in the piston (none on any of mine; my mileage was about 135K or so when I put the kit in). And you can use the pinless with the stock springs, as you found out (Sonnax doesn't spec revised springs with their pistons). BTW, the 2nd & 4th accumulator pistons are interchangeable, as they're the same exact size. Again, as far as 'difference'... I think it'll be similar to the accumulator plate revisions, and both of these way less impactful than the servo swap.

One other thing regarding the springs -- IIRC, TransGo supplied the revised / additional springs not just to increase firmness, but to guard against breakage, as they're known to break (not chronic, but it can happen). Because of this, I think I'd leave the springs as-is, if you added / swapped the revised ones in. But that's me.

One more thing that I'll add, from my own experience... the only time I wish my 1-2 was softer than it is, is when the trans fluid is cold (line pressures are higher during this time.) I sometimes adapt to this by slightly lifting my foot from the throttle right as the 1-2 shift is going to occur. This softens the shift (b/c you're manually releasing the built-up pressure.) I don't always do this (sometimes I forget; sometimes it doesn't bother me). But it's a trick you can use while the truck & its fluids are getting to operating temp.

 

[littleblazer]

I have the notched servo with the vette parts in it. The 1 2 isn't jarring but it is firm. If I had to guess the AWD makes it feel tamer than it is too so maybe I'm not the best to compare against?

 

[Sparky]

I know when I installed mine I used the recommended springs for the accumulators/servos I was installing, not what I originally had. There was not an exact match for the vette servo but one pretty close. I do not recall if I ground the notches in with vette servo or not.... you'd think after 3 times doing it I'd remember.

At any rate, 1-2 on the TB was always a bit sudden when cold, fine when warm. On the Silverado 1-2 is just firm but not jarring (unless at very heavy throttle then is squeals the serp belt for some reason). Not sure what I did different or how much is just different programming between the two vehicles.

 

[Mounce]

Update and basic end of my worries until I find another issue.

I'm either getting used to the 1-2 or it's mellowing out after the adaption table has had time to relearn. Still haven't gotten it hot enough (and probably won't until spring due to moderate ambient temps) to verify that the original 2nd gear issue is gone but I've been beating it to death and she's still trucking. I'll be surprised if the issue persisted.

Fun fact : Fluid temp hasn't made a noticeable difference on the shift since the kit. At least it's consistent lol.

 

[littleblazer]

Put a piece of cardboard in front of the cooler. That'll help.