4L60E Question

[97C1500TJ]

I’m sure this has been addressed many times already but I am having a hard shift from 1-2 gear. My first thought is the accumulator. If I get on the gas, it smoothes out but it gets to be a really hard shift otherwise. Sometimes it’s intermittent. No CEL is on the cluster to read codes. I have a Sonnax one to replace it but wanted some other opinions first. This is on my 97 C1500. The trans was rebuilt at 120K-ish and now has 225K on the odometer. No other issues with the trans since. Thank you.

 

[someotherguy]

Common issues include the accumulator piston (piston broken, spring broken), separator plate worn, or valve body wear in the TCC regulator valve bore. Here's some more info:

Old post from an experienced transmission builder on Chevytalk -

Like Richard said, get it scanned and see if any codes come up. Since you are feeling harsh shifts other than just the 1-2 it sounds like a code has been set and the computer has commanded the EPC (Electronic Pressure Control) solenoid to full line pressure. With the 1-2 feeling more harsh than the other, well, several common problems I see in these transmissions when they cross my bench will cause a harsh 1-2. One being a worn 1-2 accumulator piston and another is a worn valve body separator plate. The separator plates wear where the check balls are. The 1-2 shift check ball I commonly see either jammed in the separator plate or worn completely through the plate and sitting in the worm tracks in the case. These check balls just hammer on the separator plate wearing it out. With the accumulator pistons, they are aluminum pistons. The pin which the piston rides on is steel and commonly wears the pin bore into an egg shaped hole. The accumulator then leaks and causes a harsh 1-2. The purpose of the accumulator is to cushion the shift. If the accumulator is leaking there is no or reduced cushion effect giving you a harsh shift. Get the computer scanned and post back with the code(s). If you do get the P1870 code which is very common in these transmissions you are looking at valve body repair to fix it. If there are a lot of miles on the trans, you might want to consider an overhaul now because a valve job will cost close to half of the price to overhaul anyway.

Richard

 

[stutaeng]

I know the TCC valve body bore wear will cause this, as was stated on the quote from Richard. But it will throw that code for sure. You can probably confirm by plugging in a pressure gauge on that test port.

I ran my transmission with that issue for around 2 years. I really didn't know or understand the issue, otherwise I would have fixed it. I always figured it was bad for the transmission running all the time on full line pressure. Although mine only did it after getting off the freeway and on 1-2 shifts. By then I wasn't really driving the truck on the highway much.

Question: did it do this after the rebuild (was the rebuild done under your watch?) Or did it just start doing this?

 

[someotherguy]

You have to figure 120K for first rebuild and now it's at 225K, that 4L60E has been right on time for issues. If it doesn't have the code, my bet would be separator plate, but I'm not a trans builder so it's just a guess.

BTW the 4L65E in my SS was doing the stupid hard 1-2 shift, hard enough I felt like it was going to break something. Had 80K on the clock. Took it to my buddy to check out and he went straight for the separator plate, found wear, replaced it - and also swapped the spring on the accumulator piston as he felt it had the wrong one (like maybe p.o. went in there with a different spring intentionally trying to firm it up and went too far.) Still have a firm 1-2 shift but no longer abusively harsh. Trans finally started showing other signs of problems around 125K or so (guessing on the mileage, it's been a while) and had him build it. About a year later it started coming out of OD and the fluid was burnt; he tore it back down and found the input drum had fractured. Fixed it back up for me, no charge. One of these days it'll get a 4L80E if I keep it long enough. Just wasn't in position to do that swap when it blew up previously.

Richard

 

[97C1500TJ]

I know the TCC valve body bore wear will cause this, as was stated on the quote from Richard. But it will throw that code for sure. You can probably confirm by plugging in a pressure gauge on that test port.

I ran my transmission with that issue for around 2 years. I really didn't know or understand the issue, otherwise I would have fixed it. I always figured it was bad for the transmission running all the time on full line pressure. Although mine only did it after getting off the freeway and on 1-2 shifts. By then I wasn't really driving the truck on the highway much.

Question: did it do this after the rebuild (was the rebuild done under your watch?) Or did it just start doing this?

To my knowledge, everything was fine after the rebuild but as far back as I can remember, it’s had the 1-2 accumulator hard shift. It has just recently gotten a lot harder but only in 1-2 especially in stop and go traffic.

 

[97C1500TJ]

It sounds like I need to start setting aside money for a rebuild/replacement. What would y’all recommend? Rebuild or replace? If replace, from where?

 

[stutaeng]

Another question: did they do any "shift kit" on the rebuild? There was a thread a while back about a member saying his glovebox would pop open when the truck shifted, but he had just bought it...the PO had do done a shift kit and guy was asking how much involvement it would be to remove.

 

[97C1500TJ]

Another question: did they do any "shift kit" on the rebuild? There was a thread a while back about a member saying his glovebox would pop open when the truck shifted, but he had just bought it...the PO had do done a shift kit and guy was asking how much involvement it would be to remove.

There was some sort of shift kit installed. What kind? I don’t know. I’d have to dig out the paperwork when I get off work. It also got a new torque converter.

 

[Sabinoerc]

I had a hard and late 1-2 shift on my 92 once. I dropped pan, replaced 1-2 accumulator and/or spring , can’t remember. Still had hard shift. The suburban had been sitting and I was getting it running again and it had many problems, one of which was an surging idle. So I decided to tackle that first. Long story short, it was a marginal fuel pump. I was getting 11psi @ idle though it would drop a bit if throttle nailed. Replaced pump and got solid 13psi all the time. Fixed the surge but surprisingly also fixed the hard 1-2 shift! Somebody back then on some forum said that marginal fuel pressure can result in you putting in more throttle to maintain desired speed and PCM thinks you are trying to accelerate and delays shift. I hadn’t notice performance loss due to marginal fuel pressure as wasn’t driving the truck much but sure did notice improvements with new fuel pump.
of course, no clue if this could be contributing to your problem. I’m not knowledgeable on transmissions either. Just offering thought of something to check before rebuilding a tranny. Good luck

 

[97C1500TJ]

Update:
Today I grabbed my truck and new 1-2 piston and installed it. Not only was there a worn piston, there was a third spring that was broken. All is back together and shifting smoothly.