ATF & U-Joints
Thread Starter
Instructor
Joined: Sep 2022
Posts: 121
Likes: 24
From: Tucson, AZ
ATF & U-Joints
Hey all - got a general mechanical item, not necessarily for corvettes I suppose, just want to check with the 'net before I go bother my mechanic again.
I should start by saying that I trust him implicitly with my car - he's done every service and new part for two years and has multiple C4s in his family.
I just had the driveshaft (not half-shafts, those are fine) U-Joints done, as well as a transmission fluid change at the same time. Problem is, it's stuck in what I believe is 3rd accompanied with quite the clunk when moving into drive, but notably not reverse. Does the fluid just need a while to get back in the system or should I suspect something awry? Haven't checked the new fluid level yet, won't have a chance to go back out to it for a few hours.
Thanks as always.
I should start by saying that I trust him implicitly with my car - he's done every service and new part for two years and has multiple C4s in his family.
I just had the driveshaft (not half-shafts, those are fine) U-Joints done, as well as a transmission fluid change at the same time. Problem is, it's stuck in what I believe is 3rd accompanied with quite the clunk when moving into drive, but notably not reverse. Does the fluid just need a while to get back in the system or should I suspect something awry? Haven't checked the new fluid level yet, won't have a chance to go back out to it for a few hours.
Thanks as always.
Last edited by b_willmon_; Jul 25, 2024 at 04:39 PM.
Drifting
Joined: Sep 2022
Posts: 1,486
Likes: 395
From: Liberty, SC
2023 C4 of the Year Finalist - Unmodified
Take it back to him. I'm not a transmission expert, but the idea of it taking time for fluid to get the system isn't a thing. It'd be spread throughout the system in a matter of seconds.
Thread Starter
Instructor
Joined: Sep 2022
Posts: 121
Likes: 24
From: Tucson, AZ
I didn't think so but I am also not a transmission expert... Sometimes it's just nice to know I'm not crazy lmao. I did disconnect the battery for a bit so when I head out I'll see if the computer maybe just didn't throw a fit. If it's still having problems, back it goes 
Thread Starter
Instructor
Joined: Sep 2022
Posts: 121
Likes: 24
From: Tucson, AZ
Took it for a rip around the block - the power is being put down much better but still not as enthusiastically as I recall from a couple days ago. The pan was dropped and 5 units of fluid were replaced - all levels normal. If after driving over the weekend we still aren't acceptable I guess it's more fun times on the lift for baby blue 
Thread Starter
Instructor
Joined: Sep 2022
Posts: 121
Likes: 24
From: Tucson, AZ
More information acquired - it's starting out in 3rd, will happily shift into 4th given enough road, and will shift DOWN into 2nd while stopped and requested by shifting to '2' on the stick. Computer issue, is my guess....
Melting Slicks
Joined: Nov 2016
Posts: 2,256
Likes: 3,083
From: So Cal
2023 C4 of the Year Finalist - Unmodified
Check for codes. Some transmission codes when set cause 2nd or 3rd gear starts. Some codes default to full line pressure which could be the cause of the harsh garage shift. Transmission codes generally do not illuminate the Service Engine Soon light. But they can be flashed on the SES light. Most transmission codes are in the 80's although there are some with lower and higher numbers.
In a 1994 jumper pins 5 to 6. Turn key to RUN. Watch the SES light. 28, 81, 82, 83, 84, 90 are transmission codes of interest.
\ 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 /
\9 -10 -11-12-13-14-15-16/
In a 1994 jumper pins 5 to 6. Turn key to RUN. Watch the SES light. 28, 81, 82, 83, 84, 90 are transmission codes of interest.
\ 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 /
\9 -10 -11-12-13-14-15-16/
Thread Starter
Instructor
Joined: Sep 2022
Posts: 121
Likes: 24
From: Tucson, AZ
Sure as ****, an H84 in module 4.
2-3 solenoid circuit... which I can only assume does both up and down since if memory serves these trannies don't have a dedicated downshift solenoid(?) I'll clear the codes before work in case sitting overnight with active computers wants to get it to act up again. Full line pressure would also explain the fairly harsh 3-4 shift I managed to get out of it.
P.S. still pins 4 and 12 for '94
Thanks a ton!
2-3 solenoid circuit... which I can only assume does both up and down since if memory serves these trannies don't have a dedicated downshift solenoid(?) I'll clear the codes before work in case sitting overnight with active computers wants to get it to act up again. Full line pressure would also explain the fairly harsh 3-4 shift I managed to get out of it.
P.S. still pins 4 and 12 for '94
Thanks a ton!
Melting Slicks
Joined: Nov 2016
Posts: 2,256
Likes: 3,083
From: So Cal
2023 C4 of the Year Finalist - Unmodified
Yes, 4&12 for onboard diagnostics.
I did not know if trans codes are shown in the onboard diagnostics. So I suggested use the Check Engine Light "flash codes" method, which I know show the trans codes. To enter the PCM diagnostics, it is 5&6. 4&12 for CCM. But now I know that onboard show trans codes. Cool.
I did not know if trans codes are shown in the onboard diagnostics. So I suggested use the Check Engine Light "flash codes" method, which I know show the trans codes. To enter the PCM diagnostics, it is 5&6. 4&12 for CCM. But now I know that onboard show trans codes. Cool.
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Thread Starter
Instructor
Joined: Sep 2022
Posts: 121
Likes: 24
From: Tucson, AZ
Well the results are in - I didn't take it out because the eye-watering garage shift is still just that, and now there's an "I need U-joints" level of movement into reverse, too (may just be cold).
Codes were cleared - car started, SES still on, but the only active code was a 12 when I shut it off an interrogated it again, then the code that I just cleared was back again as still an H. I know I reset them correctly.
Unless there's a surefire way to unhook some connector from my garage to really give it a good reset I think I'll have to brave the wrath of my mechanic again... The poor guy is probably sick of me by now
Codes were cleared - car started, SES still on, but the only active code was a 12 when I shut it off an interrogated it again, then the code that I just cleared was back again as still an H. I know I reset them correctly.
Unless there's a surefire way to unhook some connector from my garage to really give it a good reset I think I'll have to brave the wrath of my mechanic again... The poor guy is probably sick of me by now
Melting Slicks
Joined: Nov 2016
Posts: 2,256
Likes: 3,083
From: So Cal
2023 C4 of the Year Finalist - Unmodified
With a bad 3-2 Control solenoid (the coil resistance is open or shorted) you can't "reset" anything. The code and the actions taken (3rd gear start, full line pressure) come right back.
It is possible to measure the solenoid resistances between the PCM connectors and the "output" side of the removed Fuse 17 (should be VALET).
3-2 Control: White wire, Cavity B13, Black connector.
1-2 Shift: Lt green wire, Cavity B7, Black connector.
2-3 Shift: Yel/blk wire, Cavity B12, Black connector.
TCC Solenoid: Tan/blk wire, Cavity D11, Blue connector.
I don't recall what the exact acceptable resistance range is for these solenoids. Probably in the 12-30 Ohms range.
While out running errands, my DD all of a sudden began 3rd gear starts. I checked for codes as soon as I got back to the house. I had the code for the 3-2 control solenoid. I took another car to the parts house, obtained the solenoid and returned and installed it. Less than 2 hours from onset of the problem to fixed. The faulty solenoid measured infinite ohms.
It is possible to measure the solenoid resistances between the PCM connectors and the "output" side of the removed Fuse 17 (should be VALET).
3-2 Control: White wire, Cavity B13, Black connector.
1-2 Shift: Lt green wire, Cavity B7, Black connector.
2-3 Shift: Yel/blk wire, Cavity B12, Black connector.
TCC Solenoid: Tan/blk wire, Cavity D11, Blue connector.
I don't recall what the exact acceptable resistance range is for these solenoids. Probably in the 12-30 Ohms range.
While out running errands, my DD all of a sudden began 3rd gear starts. I checked for codes as soon as I got back to the house. I had the code for the 3-2 control solenoid. I took another car to the parts house, obtained the solenoid and returned and installed it. Less than 2 hours from onset of the problem to fixed. The faulty solenoid measured infinite ohms.
Thread Starter
Instructor
Joined: Sep 2022
Posts: 121
Likes: 24
From: Tucson, AZ
Understood, I'm very grateful for the advice... I don't have the facilities at home to get inside the pan so back to the doc she goes - I'll ask him flat out to start with that, and to check pressures as well as electrical resistance.
I do find it very interesting that this started after a fluid change... I recall reading that on these old things it's best to simply not change it, but I'd rather open a can of worms and fix what's 'just being held together' instead of the if it ain't broke don't fix it approach, at least in this instance.
I do find it very interesting that this started after a fluid change... I recall reading that on these old things it's best to simply not change it, but I'd rather open a can of worms and fix what's 'just being held together' instead of the if it ain't broke don't fix it approach, at least in this instance.
Instructor
Joined: Dec 2023
Posts: 166
Likes: 73
From: Indiana
I'm confused. Is your question about the 700r4 in your vette? It would be strange to have this issue right after the trans fluid change. If it was me i would drop the trans pan and be sure the filter is seated all the way in. And make sure the old filter oring isn't holding the filter from seating. You need to really press it in and some older 700r4 pans need to be replaced as they were shallow and would crush the filter. This could starve the trans of fluid and could toast your trans if driven a lot.
Thread Starter
Instructor
Joined: Sep 2022
Posts: 121
Likes: 24
From: Tucson, AZ
Solved! Shoulda grabbed a picture of it.... the little pin-connector on the 3-2 solenoid sheared clean off after the fluid change. The old filter was so clogged that proper pressure was just too much for the little thing at its age. Thanks for the tips! My mechanic doesn't really do trannies and almost sent me up the road to someone he recommended, but I asked if he could just try the quick part swap and voila!
Turns out it was a vette question after all! I didn't know trans codes wouldn't always pop the SES, so I'd really have been stumped!
Turns out it was a vette question after all! I didn't know trans codes wouldn't always pop the SES, so I'd really have been stumped!
Instructor
Joined: Dec 2023
Posts: 166
Likes: 73
From: Indiana
Solved! Shoulda grabbed a picture of it.... the little pin-connector on the 3-2 solenoid sheared clean off after the fluid change. The old filter was so clogged that proper pressure was just too much for the little thing at its age. Thanks for the tips! My mechanic doesn't really do trannies and almost sent me up the road to someone he recommended, but I asked if he could just try the quick part swap and voila!
Turns out it was a vette question after all! I didn't know trans codes wouldn't always pop the SES, so I'd really have been stumped!
Turns out it was a vette question after all! I didn't know trans codes wouldn't always pop the SES, so I'd really have been stumped!