4L60E - Changing Gear from D to R with with hard stack/kick

[gboos]

Hi members,

I have just one question related to our well known and nice transmission 4L60E.

Some friends of mine and I experienced a hard kick/stack when changing the gear from D to R with our 4.2L TB's and Tahoes. We all got different answers for our questions from different garages. Some are saying there's no problem and it's normal. Some are saying there's a problem with the servo in the transmission etc etc.. But we can't figure out there is a real problem and if so which problem it is. I for myself can say that if I change the gear from D to R over N smoothly I don't feel these hacks/stacks. But when I change/push it hard from D to R I feel the hack/stack as well.

Would be nice to get a serious and helpful answer.

Thank you in advance.

My regards.

Mike

 

[dfc739]

Hi members,

I have just one question related to our well known and nice transmission 4L60E.

Some friends of mine and I experienced a hard kick/stack when changing the gear from D to R with our 4.2L TB's and Tahoes. We all got different answers for our questions from different garages. Some are saying there's no problem and it's normal. Some are saying there's a problem with the servo in the transmission etc etc.. But we can't figure out there is a real problem and if so which problem it is. I for myself can say that if I change the gear from D to R over N smoothly I don't feel these hacks/stacks. But when I change/push it hard from D to R I feel the hack/stack as well.

Would be nice to get a serious and helpful answer.

Thank you in advance.

My regards.

Mike

I don't believe the servo theory. The servo is only applicable to shifts involving the band. The servo is basically a piston that when fluid pressure is applied, it forces the band to become tight around the drum. This occurs on the 1-2 and 3-4 shifts. It also has an effect on the releasing of the band (the 2-3 shift).

I had a very similar situation with my transmission where when I put it into reverse or drive I would get what I describe as a "clunk". When I put in my shift kit and new accumulator pistons it fixed it and I have no more clunk. You can hardly even tell I put it into reverse/drive actually. I'm going to put my money on either a very worn separator plate or the forward/reverse accumulator piston or spring are bad. The forward/reverse accumulator piston is meant to smooth out line pressure, but if it's busted doesn't do a very good job. It's represented in Pic 10 of my write-up http://gmtnation.com/f93/how-remove-4l60e-valve-body-replace-plastic-accumulator-pistons-4972/. You might be able to replace this without dropping the valve body but it will be difficult as one of the three bolts holding the plate on will be very close to the case. I'll take a look when I get home tonight.

Dan

 

[gboos]

Dan ... many thanks for the quick reply. Much appreciated. Will discuss it with the guy's here. Again ... Thx a lot.

Greetings.

Mike

 

[McGMT]

How many miles do you have on the clock? Would help narrow down some possibilities depending on a few things there are some hardparts to consider in this situation.

 

[gmcman]

A friend of mine who owned 2 transmission shops, said he would overhaul 10 4L60E's/700R4 trannys to 1 Ford 4R70/75. Main reason was band failure then clutch failure mostly from worn seperator plates and other smaller areas like pistons....among other things. I'm not saying everyone is dishonest, but if you take a trans to a shop that's slipping more than likely they will try to sell you a rebuild, and it may have life left in it.

Once you get pressure loss then the game is over, if not remedied quickly then you will start burning up clutches and/or breaking hard parts, hopefully in your case the hard parts are ok.

Like dfc stated, could be something simple and his write up was great. This is what I found when I pulled my valve body, very easy to do just messy.

The check balls were hammered deep into the seperator plate, the one check ball from the 1-2 accumulator which sits above the plate, was basically pushed through. When I pulled the valve body the check ball was looking at me and just as I turned my head....I heard "TINK" and then needed to locate it, should have been above the plate.

Here is what the rest of the seats looked like, main reason for my problems. The arrow on the right was just for reference of the plate thickness, no ball there.

I did replace the 1-2 and 2-3 piston since they were cheap and not sure how well the O-rings were sealing.

I would at least pull the valve body and take a look.

 

[McGMT]

I guess he dis-appeared. I wish I knew what kind of mileage he had and all. I mean I have seen input shaft damage, sun gears missing teeth, and everything in between. I have even seen some trans with factory defects like the shim packs not being correct, had one with that problem and at 47,000mi one of the sun gears stripped from all the play.

And don't even get me started on Ford trannys.. They had a BIG problem with the servo bores on those.. The piston shaft bore would egg out and let fluid bypass so you would lose gears. Almost NO part replacer type of tranny shop (The Re-Builders) could figure it out, "rebuild it" 2 or 3 times before they replace it in disgust. Simple as a $30 bushing kit to bore out the tranny case and install harder bushings. I HATE when I hear someone going to some "Transmission Guy" and instantly are told it needs a rebuild....

 

[dfc739]

A friend of mine who owned 2 transmission shops, said he would overhaul 10 4L60E's/700R4 trannys to 1 Ford 4R70/75. Main reason was band failure then clutch failure mostly from worn seperator plates and other smaller areas like pistons....among other things. I'm not saying everyone is dishonest, but if you take a trans to a shop that's slipping more than likely they will try to sell you a rebuild, and it may have life left in it.

Once you get pressure loss then the game is over, if not remedied quickly then you will start burning up clutches and/or breaking hard parts, hopefully in your case the hard parts are ok.

That's exactly what got me started on working on my transmission. Local hack of a transmission shop told me it would be at least $500 to fix the transmission and probably closer to $2500 for a rebuild (he was pushing for this). I didn't like that I thought the transmission was a black box of voodoo and that's how it transferred the engine power to the driveshaft. Instead, I'm studying it and learning how it works so I will know how it can fail.

Oh, and I'm pretty sure you can get to the bolts holding the forward accumulator in. So you don't even need to drop the valve body to change it.

 

[gboos]

Many thanks for all the replies. I have around 76000km on my 01/2005 4.2L with this transmission.

But it all seems ok when I'm pushing from D to R with a short "stop" on N. When I was going forward, breaking/stopping and then pushing it immediately from D to R directly without making a stop in N, then I get a hard kick. So I adjusted to the smooth style to not stress the still rotating parts way too much after breaking and stopping.

Thanks a lot.

Mike