Another 4L60E Down: P1870, Hard 1-2 Shift, What should I do?

shovenose

Original poster
Member
Apr 24, 2016
318
SF Bay Area, CA
Not sure how much I've posted about my $600 Suburban, but the short version is it took a lot of parts, time, money, and stuff to get it back on the road. Been joyfully driving this thing for a whole two days (about 400 miles) before the 4L60E betrayed me... I was stuck in traffic and noticed that the 1-2 shift was a little hard. Well by the time I got there I was going the 1-2 shift went from a little annoying to REALLY hard, and the service engine soon light came on. Like, the whole truck would jolt. A little research online turned up this: "If at some point the transmission begins to slip, P1870 sets and line pressure is elevated in an attempt to stop any further slippage and prevent further damage. This would explain why DTC 1870 is often accompanied by a complaint of a hard 1-2 upshift."

Now, it seems that most likely I just need to change the valve body, which would run me about $180, then with new fluid and filter and stuff maybe $250: https://www.ebay.com/itm/4L60E-4L65...SS-OEM-CHEVY-GMC-1996-2002-P1870/122937609899

Thing is, I don't have a garage or lift, so I probably can't do it myself, and I assume it's gonna run me about 2 hours of labor at a shop, which is like another $250. So we're $500 into the original 213K+ mile 4L60E with questionable maintenance history. And, of course, no guarantees this fixes the problem. Then, I've thrown away $500 just to need a whole new transmission anyway.

Having a new remanufactured stock replacement transmission installed would run me about $2500 I'm guessing. I'm going to keep this truck for a long time so I'm thinking of just parking it and saving up for that, but part of me wants to try to fix the old transmission first. Either way, it's getting fixed. I have a different vehicle to drive so it's not like I'm without wheels.

I would really like some input on which option I should take.
 

Reprise

Lifetime VIP Donor
Supporting Donor
Member
Jul 22, 2015
2,724
Since you know she's a keeper, put the transgo kit in, or replace the VB outright.

If you go for the second option, make sure you get one with the TCC fix already done (a lot of them put in the Sonnax fix, which is an overbored / sleeved /oversized valve. Either way solves your issue.

Easier to spend a couple hundred if you know the alternative is 10x that amount, and has a better than 50/50 chance of fixing the problem (permanently). I'd actually rate about 80% probability of a good outcome. Only issue is that you've got 215K on the trans, so that is a risk (that something else breaks).

In the event it doesn't fix, or dies from another issue, then you spend the price for the full rebuild, which you were prepared to do anyway. If the TCC / 1870 issue was your only one, I'd go this route, having done it myself (including the full rebuild after, but that was my fault, due to fluid starvation)

Since you'll be in there, may as well put in a new separator plate and replace any plastic accumulators (the VB should have a new fwd accumulator piston already in, if you do the reman option)
 
Last edited:

littleblazer

Member
Jul 6, 2014
9,265
The 3500 did this randomly with the 4l80e. (before it dropped a valve) I was informed by a tech that a valve cover or any type of oil leak could get into the electrical connectors and trip it. Ours was intermittent though. That being said I have the trans go shift kit sitting in a box for when we drop the 383 in. I highly doubt it's the issue on mine or yours but it's easy enough to see if everything is saturated.
 

shovenose

Original poster
Member
Apr 24, 2016
318
SF Bay Area, CA
Thanks all, so from reading that link this is what I need, if I decide to keep the existing transmission (of course in addition to a filter kit and a case of Dex VI).

https://www.ebay.com/itm/4L60E-4L65...ash=item3f1166b953:g:WDkAAOSwpDdVeOGx&vxp=mtr

I'm going to check with a few shops 1. if they would do it for me (of course I would make it clear if my trans is still messed up afterward it's not their fault) and 2. how much it would cost. I really should try to do it myself but I don't think that's gonna end well, so I'm going to take it in.

However, I checked the exact price of a whole replacement trans, and it only costs me $1200+tax+fluid, BUT it won't install itself - still I will see how much a shop would charge to install it for me - it might be the smarter choice to just save up for that since I don't need it done anytime soon. Such a tough choice :/

yAlnNJk.png
 

Reprise

Lifetime VIP Donor
Supporting Donor
Member
Jul 22, 2015
2,724
That is, indeed, the kit we all talk about and have installed ourselves. That one's the 'deluxe' version, as it has the vette servo along with the ATSG service manual. Good stuff (although it looks like he's gone up on his prices a little since I bought mine.)

As for installing...only you know what your capabilities are. For me, although I had done a few filter changes on THM350s & 400s way back when, I had never removed a VB before. I did wrestle w/ myself for a while about whether I could do it correctly.

As it turned out, I did a great job (although a little slow, but my Voy isn't my DD). My problem was not accounting for the extra fluid draining out during that time, and thinking that the standard 5qts were enough. They weren't, and I smoked my clutch packs & burnt up the internals. But that was my fault 100%.

For the 1st 36hrs, until I took it on the interstate, it worked just like the kit described (I had no codes, but I did have a harsh 1-2 shift.)

So...although my experience was limited, I got it installed (minus the vette servo; it went in during the full rebuild) Maybe that will provide some insight for you.

With all of that said...w/ 215k on the trans, if you feel better having the whole rebuild done, I don't think anyone would strenuously argue the point. I'd have the weaker points addressed; you can find my previous posts describing that, so I'll keep from typing it here yet again.

Figure $500 - 600 or so for labor to swap old for new. One thing I'd avoid doing is taking it to the shop for the smaller kit and telling them " no big deal if it doesn't work"; that almost invites them to behave unethically and not install the kit at all, but charge you for it (figure labor on that to be $300 & up, but that's an admittedly WAG on my part.)
 
Last edited:

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
I also did it for the first time on my '02 and it went fine except I think I screwed up on drilling out a hole and made the 1-2 shift harsh. I know now to leave it alone. Our buddy in France @trailblazer075 had never done anything like this but did it. He did forget to reconnect the internal shift linkage but went back and fixed it. Loves it.
 

mntegra01

Member
Mar 26, 2018
86
Virginia
I would have to know more history on the trans. Has it ever been replaced or rebuilt? I bought a 2003 2wd trailblazer and found pump had shattered. Once I opened it up more I found the forward sprag almost toast. I rebuilt mine with new GM parts (@10 over cost) and overhaul kits etc etc, and still spent $1400.

My experience with a P1870 is a TCC slip code. Cut turbine shaft seal, input drum seals cut, there's a fluid pressure loss somewhere the computer can read. Could be a torque converter, TCC solenoid valve in valve body..... I totally overhauled my trans with 184,000 miles and still had a P1870 after rebuild. I replaced the internal harness which has TCC solenoid built to it, the PWM solenoid and the force motor or pressure solenoid. That fixed my P1870. I did however, do the Sonnax valve reaming foe the TCC bore.

Check out LS1tech forums and youtube 4l60e transmission bench videos, and also Hiram at Automatic Transmissions on YouTube. Very detailed and you can do your own overhaul if you feel inclined.

Just depends on what you want as far as time/money VS warranty. We sell GM 3yr/100k warranty trans for probably around $1700 often, could be cheaper, just depends on VIN and model of the hydra-matic. 2wd,4wd etc. See if you can find a dealer that does truckload trans for less than GM cost.

-Mac
 

shovenose

Original poster
Member
Apr 24, 2016
318
SF Bay Area, CA
I would have to know more history on the trans. Has it ever been replaced or rebuilt? I bought a 2003 2wd trailblazer and found pump had shattered. Once I opened it up more I found the forward sprag almost toast. I rebuilt mine with new GM parts (@10 over cost) and overhaul kits etc etc, and still spent $1400.

My experience with a P1870 is a TCC slip code. Cut turbine shaft seal, input drum seals cut, there's a fluid pressure loss somewhere the computer can read. Could be a torque converter, TCC solenoid valve in valve body..... I totally overhauled my trans with 184,000 miles and still had a P1870 after rebuild. I replaced the internal harness which has TCC solenoid built to it, the PWM solenoid and the force motor or pressure solenoid. That fixed my P1870. I did however, do the Sonnax valve reaming foe the TCC bore.

Check out LS1tech forums and youtube 4l60e transmission bench videos, and also Hiram at Automatic Transmissions on YouTube. Very detailed and you can do your own overhaul if you feel inclined.

Just depends on what you want as far as time/money VS warranty. We sell GM 3yr/100k warranty trans for probably around $1700 often, could be cheaper, just depends on VIN and model of the hydra-matic. 2wd,4wd etc. See if you can find a dealer that does truckload trans for less than GM cost.

-Mac

Hi,

I have no history at all on this transmission as I recently purchased the vehicle with no maintenance history or paperwork. The guy I bought it from had bought it from somebody else who bought it as a lien sale from a tow yard because it was totaled out after an accident in 2013... so basically I know nothing about it.
 

snogroomer

Member
Mar 28, 2018
1
Kellogg Idaho
Not sure how much I've posted about my $600 Suburban, but the short version is it took a lot of parts, time, money, and stuff to get it back on the road. Been joyfully driving this thing for a whole two days (about 400 miles) before the 4L60E betrayed me... I was stuck in traffic and noticed that the 1-2 shift was a little hard. Well by the time I got there I was going the 1-2 shift went from a little annoying to REALLY hard, and the service engine soon light came on. Like, the whole truck would jolt. A little research online turned up this: "If at some point the transmission begins to slip, P1870 sets and line pressure is elevated in an attempt to stop any further slippage and prevent further damage. This would explain why DTC 1870 is often accompanied by a complaint of a hard 1-2 upshift."

Now, it seems that most likely I just need to change the valve body, which would run me about $180, then with new fluid and filter and stuff maybe $250: https://www.ebay.com/itm/4L60E-4L65...SS-OEM-CHEVY-GMC-1996-2002-P1870/122937609899

Thing is, I don't have a garage or lift, so I probably can't do it myself, and I assume it's gonna run me about 2 hours of labor at a shop, which is like another $250. So we're $500 into the original 213K+ mile 4L60E with questionable maintenance history. And, of course, no guarantees this fixes the problem. Then, I've thrown away $500 just to need a whole new transmission anyway.

Having a new remanufactured stock replacement transmission installed would run me about $2500 I'm guessing. I'm going to keep this truck for a long time so I'm thinking of just parking it and saving up for that, but part of me wants to try to fix the old transmission first. Either way, it's getting fixed. I have a different vehicle to drive so it's not like I'm without wheels.

I would really like some input on which option I should take.
Have you tried testing the TCC PWM solenoid at the right front corner inside the pan? Or it could just be a blown fuse. Also checked the main electrical connection up on the upper side of the transmission.
 

Blackwater

Member
Aug 14, 2015
477
Lawton, OK
Thanks all, so from reading that link this is what I need, if I decide to keep the existing transmission (of course in addition to a filter kit and a case of Dex VI).

https://www.ebay.com/itm/4L60E-4L65...ash=item3f1166b953:g:WDkAAOSwpDdVeOGx&vxp=mtr

I'm going to check with a few shops 1. if they would do it for me (of course I would make it clear if my trans is still messed up afterward it's not their fault) and 2. how much it would cost. I really should try to do it myself but I don't think that's gonna end well, so I'm going to take it in.

However, I checked the exact price of a whole replacement trans, and it only costs me $1200+tax+fluid, BUT it won't install itself - still I will see how much a shop would charge to install it for me - it might be the smarter choice to just save up for that since I don't need it done anytime soon. Such a tough choice :/

yAlnNJk.png
350 to 400 from the salvage yard
 

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