94 c4 trans slipping
Melting Slicks
Joined: Feb 2003
Posts: 2,677
Likes: 812
From: Saskatoon Sask.
I drove it again. I'll be as specific as I can. Reverse seems fine . I held the brake, increased rpms and no slippage. I also did the same in drive, (first gear), no slippage.
Starting out in drive at normal driving speed the car starts out normal. Then it seems it just doesnt want to upshift. It holds first and then around 2100 rpms or so it just starts slipping badly. If you let the gas off it seems to go into 3rd. I got it up to about 60 and it seemed 3rd and 4th were OK and I think even the TC locked up. Its hard to tell exactly because I'm on rough roads and I'm driving a corvette. lol. Also, I dont want to drive it that much because of its condition.
So, from a stop manually shifting gears. It will hold 1st fine. Manually shifting to second it just goes into full slip. Shifting it into 3rd seems OK.
From the link that Numake posted could it be a broken band or a short/worn servo pin? I know you guys know much more than I do about the 4l60e and I appreciate the comments. I'm really hoping this isnt destined for a complete overhaul. I dont have a lift. I have a gravel driveway.lol..
Starting out in drive at normal driving speed the car starts out normal. Then it seems it just doesnt want to upshift. It holds first and then around 2100 rpms or so it just starts slipping badly. If you let the gas off it seems to go into 3rd. I got it up to about 60 and it seemed 3rd and 4th were OK and I think even the TC locked up. Its hard to tell exactly because I'm on rough roads and I'm driving a corvette. lol. Also, I dont want to drive it that much because of its condition.
So, from a stop manually shifting gears. It will hold 1st fine. Manually shifting to second it just goes into full slip. Shifting it into 3rd seems OK.
From the link that Numake posted could it be a broken band or a short/worn servo pin? I know you guys know much more than I do about the 4l60e and I appreciate the comments. I'm really hoping this isnt destined for a complete overhaul. I dont have a lift. I have a gravel driveway.lol..
Thread Starter
Advanced
Joined: Dec 2020
Posts: 64
Likes: 2
From: florida
There is no going to Autozone for a can of "trans refresher". Something is fkd and it needs to be diagnosed. Repeat, repeat...pressure tests!! Your band is not broken or else you wouldn't have 4th gear. I'm not convinced you know the meaning of "slip". There is a difference between "not engaged" and "slip". I'll say this for the THIRD time. If your band is slipping, you remain somewhat in 1st gear until your speed reaches high enough to engage 3rd.
"If your band is slipping, you remain somewhat in 1st gear until your speed reaches high enough to engage 3rd" Yeh, thats basically what its doing and if you give it throttle it will slip/not engage until it gets into 3rd.
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
I drove it again. I'll be as specific as I can. Reverse seems fine . I held the brake, increased rpms and no slippage. I also did the same in drive, (first gear), no slippage.
Starting out in drive at normal driving speed the car starts out normal. Then it seems it just doesnt want to upshift. It holds first and then around 2100 rpms or so it just starts slipping badly. If you let the gas off it seems to go into 3rd. I got it up to about 60 and it seemed 3rd and 4th were OK and I think even the TC locked up. Its hard to tell exactly because I'm on rough roads and I'm driving a corvette. lol. Also, I dont want to drive it that much because of its condition.
So, from a stop manually shifting gears. It will hold 1st fine. Manually shifting to second it just goes into full slip. Shifting it into 3rd seems OK.
From the link that Numake posted could it be a broken band or a short/worn servo pin? I know you guys know much more than I do about the 4l60e and I appreciate the comments. I'm really hoping this isnt destined for a complete overhaul. I dont have a lift. I have a gravel driveway.lol..
Starting out in drive at normal driving speed the car starts out normal. Then it seems it just doesnt want to upshift. It holds first and then around 2100 rpms or so it just starts slipping badly. If you let the gas off it seems to go into 3rd. I got it up to about 60 and it seemed 3rd and 4th were OK and I think even the TC locked up. Its hard to tell exactly because I'm on rough roads and I'm driving a corvette. lol. Also, I dont want to drive it that much because of its condition.
So, from a stop manually shifting gears. It will hold 1st fine. Manually shifting to second it just goes into full slip. Shifting it into 3rd seems OK.
From the link that Numake posted could it be a broken band or a short/worn servo pin? I know you guys know much more than I do about the 4l60e and I appreciate the comments. I'm really hoping this isnt destined for a complete overhaul. I dont have a lift. I have a gravel driveway.lol..
And if you read the link I provided and came away from it thinking "the band is broken," I'm not sure what to tell you except that you need to slow down and read a lot more carefully. That was quite literally the exact opposite of what it said. As arbee stated, a broken band would mean you wouldn't have 4th at all. If you have 4th, it literally cannot be a broken band.
What I can tell you is that according to your logs, the PCM is absolutely commanding second gear. There's no data value for "shift completed" on the 94-96 4L60E, and I'd need to do some testing on my own to be able to interpret the "start of shift" and "end of shift" parameters that are logged to see what 'normal' looks like versus your log. As I've said before, from a glance, the electronics seem to be unconcerned and appear to be performing exactly as commanded. You have a mechanical issue, likely a result of a shoddy rebuild. It makes me wonder if the shop that did the rebuild is also responsible for your electrical gremlins too.
EDIT: I found a diagnostic manual for the '96 4L60E that explained the "Start of Shift" and "End of Shift" parameters. They only apply to upshifts, not downshifts. So the kickdown from 4 to 2 isn't handled by those values. Really too bad the '94 doesn't have the "shift completed" parameter. It would be interesting to see if the transmission actually thinks the 2nd gear shifts get completed according to its internal logic.
Last edited by Nomake Wan; May 4, 2021 at 01:16 PM.
Thread Starter
Advanced
Joined: Dec 2020
Posts: 64
Likes: 2
From: florida
Please pay attention to what arbee and IHBD have been trying desperately to tell you this whole thread long. Both of them have torn these transmissions apart. They're both well aware of how they function and how to diagnose problems. They've both told you several times now what tests you need to perform. I recommend you actually perform those tests.
And if you read the link I provided and came away from it thinking "the band is broken," I'm not sure what to tell you except that you need to slow down and read a lot more carefully. That was quite literally the exact opposite of what it said. As arbee stated, a broken band would mean you wouldn't have 4th at all. If you have 4th, it literally cannot be a broken band.
What I can tell you is that according to your logs, the PCM is absolutely commanding second gear. There's no data value for "shift completed" on the 94-96 4L60E, and I'd need to do some testing on my own to be able to interpret the "start of shift" and "end of shift" parameters that are logged to see what 'normal' looks like versus your log. As I've said before, from a glance, the electronics seem to be unconcerned and appear to be performing exactly as commanded. You have a mechanical issue, likely a result of a shoddy rebuild. It makes me wonder if the shop that did the rebuild is also responsible for your electrical gremlins too.
EDIT: I found a diagnostic manual for the '96 4L60E that explained the "Start of Shift" and "End of Shift" parameters. They only apply to upshifts, not downshifts. So the kickdown from 4 to 2 isn't handled by those values. Really too bad the '94 doesn't have the "shift completed" parameter. It would be interesting to see if the transmission actually thinks the 2nd gear shifts get completed according to its internal logic.
And if you read the link I provided and came away from it thinking "the band is broken," I'm not sure what to tell you except that you need to slow down and read a lot more carefully. That was quite literally the exact opposite of what it said. As arbee stated, a broken band would mean you wouldn't have 4th at all. If you have 4th, it literally cannot be a broken band.
What I can tell you is that according to your logs, the PCM is absolutely commanding second gear. There's no data value for "shift completed" on the 94-96 4L60E, and I'd need to do some testing on my own to be able to interpret the "start of shift" and "end of shift" parameters that are logged to see what 'normal' looks like versus your log. As I've said before, from a glance, the electronics seem to be unconcerned and appear to be performing exactly as commanded. You have a mechanical issue, likely a result of a shoddy rebuild. It makes me wonder if the shop that did the rebuild is also responsible for your electrical gremlins too.
EDIT: I found a diagnostic manual for the '96 4L60E that explained the "Start of Shift" and "End of Shift" parameters. They only apply to upshifts, not downshifts. So the kickdown from 4 to 2 isn't handled by those values. Really too bad the '94 doesn't have the "shift completed" parameter. It would be interesting to see if the transmission actually thinks the 2nd gear shifts get completed according to its internal logic.
Nice job condescending. I said I dont know anything about transmissions. From your link: "If the transmission still has no 2nd with test snout installed. Inspect the servo pin length (too short), the band anchor hole for wear or an elongated anchor hole, a mismatch between 2nd gear piston and housing or the servo sealing rings are damaged or undersized."
Band anchor hole wear, elongated anchor hole to me equals broken. I also asked about the servo pin length. The link you gave me was from GM.
"They've both told you several times now what tests you need to perform."
And one of them asked how it was in reverse so I drove it again and reported back. As for pressure tests I said I was going to do that. You didnt see that post?
I guess I should just stop posting about it. You guys just get pissed off.
Melting Slicks
Joined: Feb 2003
Posts: 2,677
Likes: 812
From: Saskatoon Sask.
Semantics... Call it what you want. I described it as best as I can.
"If your band is slipping, you remain somewhat in 1st gear until your speed reaches high enough to engage 3rd" Yeh, thats basically what its doing and if you give it throttle it will slip/not engage until it gets into 3rd.
"If your band is slipping, you remain somewhat in 1st gear until your speed reaches high enough to engage 3rd" Yeh, thats basically what its doing and if you give it throttle it will slip/not engage until it gets into 3rd.
Thread Starter
Advanced
Joined: Dec 2020
Posts: 64
Likes: 2
From: florida
No, it fkn well ISN'T semantics. Everything that has been asked of you had a reason. You picked the wrong dude if you think you are going to come at me with your butthurt attitude. I was more than willing to help you find your problem but you just killed any more thoughts of that.
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
Nice job condescending. I said I dont know anything about transmissions. From your link: "If the transmission still has no 2nd with test snout installed. Inspect the servo pin length (too short), the band anchor hole for wear or an elongated anchor hole, a mismatch between 2nd gear piston and housing or the servo sealing rings are damaged or undersized."
Band anchor hole wear, elongated anchor hole to me equals broken. I also asked about the servo pin length. The link you gave me was from GM.
I guess I should just stop posting about it. You guys just get pissed off.
Band anchor hole wear, elongated anchor hole to me equals broken. I also asked about the servo pin length. The link you gave me was from GM.
I guess I should just stop posting about it. You guys just get pissed off.
The band anchor hole being worn does not a broken band make. Defective yes, broken no. Again, there is an incredibly important difference.
Anyway, please remember that we are not the ones with the problem which needs diagnosing and repairing, you are. If you want to stop posting, feel free, it's your car. I'm helping as best I can, as were arbee and IHBD.
Best of luck.
Thread Starter
Advanced
Joined: Dec 2020
Posts: 64
Likes: 2
From: florida
You're welcome, I guess. "Broken band" has a very specific meaning--it means that the actual band is broken. If the band is broken, there will no longer be anything to actuate. 2nd and 4th will vanish instantly, and you'll find pieces of the band in the transmission pan.
The band anchor hole being worn does not a broken band make. Defective yes, broken no. Again, there is an incredibly important difference.
Anyway, please remember that we are not the ones with the problem which needs diagnosing and repairing, you are. If you want to stop posting, feel free, it's your car. I'm helping as best I can, as were arbee and IHBD.
Best of luck.
The band anchor hole being worn does not a broken band make. Defective yes, broken no. Again, there is an incredibly important difference.
Anyway, please remember that we are not the ones with the problem which needs diagnosing and repairing, you are. If you want to stop posting, feel free, it's your car. I'm helping as best I can, as were arbee and IHBD.
Best of luck.
When I said "broken" I meant that in the way of needing replacement. Really not that hard to string "broken" and needing replacement together.
Anyway, I'm out..
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Melting Slicks
Joined: Feb 2003
Posts: 2,677
Likes: 812
From: Saskatoon Sask.
That is an interesting thread. The OP and the main responder both are familiar with the 4L60 and 60e. I have never encountered a "no 2nd, but has 4th". Those guys suggested that the 4th servo has more travel than the 2nd gear portion, and that a longer pin (or adding weld to the existing pin) could restore 2nd for awhile.
I went out to the shop and messed with a servo I have in my stash. Without putting it in a case (I'm lazy, the only empty case I have is difficult to access in the rafters) the results are sort of inconclusive, but it appears that there is indeed about .040-.060 more travel in 4th. So I learned something today, and have something to investigate the next time I have a case in front of me.
My experience has been that the bands don't wear much at all. They are still in great reusable shape long after the 3-4 has expired after 100k or more of service. If your trans with 8,000 miles on it has worn your band enough to cause a loss of 2nd, there is something wrong, possibly a pressure drop somewhere in the 2nd or 4th circuits involving the accumulators or servo assembly.
A look in the pan for friction material would be confirmation. The guys in the linked thread indicated that the band CAN be wiggle checked with the Valve Body installed, and that the drum condition is visible. (Yesterday, I wasn't sure if the band is visible with the VB installed. It seems that it IS.) A pressure check is pretty much mandatory to figure out what you need to do prior to addressing the cure for "no 2nd" particularly if the band has worn significantly in only 8,000 miles. If you can do it safely, with the engine running, shifter in D2, IF pressing on the servo cover with a pry-bar results in a "shift" to 2nd (have the helper in the driver seat confirm the speedometer reading goes up) then the "worn band" is probable.
Good luck.
I went out to the shop and messed with a servo I have in my stash. Without putting it in a case (I'm lazy, the only empty case I have is difficult to access in the rafters) the results are sort of inconclusive, but it appears that there is indeed about .040-.060 more travel in 4th. So I learned something today, and have something to investigate the next time I have a case in front of me.
My experience has been that the bands don't wear much at all. They are still in great reusable shape long after the 3-4 has expired after 100k or more of service. If your trans with 8,000 miles on it has worn your band enough to cause a loss of 2nd, there is something wrong, possibly a pressure drop somewhere in the 2nd or 4th circuits involving the accumulators or servo assembly.
A look in the pan for friction material would be confirmation. The guys in the linked thread indicated that the band CAN be wiggle checked with the Valve Body installed, and that the drum condition is visible. (Yesterday, I wasn't sure if the band is visible with the VB installed. It seems that it IS.) A pressure check is pretty much mandatory to figure out what you need to do prior to addressing the cure for "no 2nd" particularly if the band has worn significantly in only 8,000 miles. If you can do it safely, with the engine running, shifter in D2, IF pressing on the servo cover with a pry-bar results in a "shift" to 2nd (have the helper in the driver seat confirm the speedometer reading goes up) then the "worn band" is probable.
Good luck.