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Discussion Starter · #1 ·
i have searched quite a bit on this subject and its seems my problems are very similar to some peoples, but i have one i havent found any info on

im 90% sure my TC is bad, it shudders in OD,drive, and in 2nd and a pulls a 628(lockup error)

but the wierd thing is that when i manually drop the tranny into 1st, there is no shudder no slippage no nothing just fine, then from there i can manually bump it up to second or OD and it will slip and what not

but if the TC was bad, what would make it not slip in manual 1st gear?

could the MLPS make 1st work ok and not the rest of them, or could i have a clogged valvebody or what not?
 

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Satyr of the Midwest
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According to an E4OD shift schedule I have, 1st-gear torque converter lockup isn't possible. At least it's not part of the PCM's mapping.

If you start from a standing stop, and accelerate slowly, does your transmission go: 1st, 2nd @ ~18mph, 3rd @ ~25mph, then an attempt at torque converter lockup @ 30mph? That's partially how I determined my TC clutch to be bad.
 

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Discussion Starter · #3 ·
ok well i get what you saying but something has to lock up in the torque converter b/c thats the only thing connect the spinning trans to the flex plate

honestly i dont know exactly how they work, but from a dead stop theres a lot of intial slippage and shuddering, i assumed TC

another question does that 628 mean that high speed TC lock up like what your saying, or does it mean low speed taking off problems etc.

i will have to check my mph's and shifts and get back w/ you
 

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Satyr of the Midwest
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quiefinator said:
ok well i get what you saying but something has to lock up in the torque converter b/c thats the only thing connect the spinning trans to the flex plate
If that were true, then none of the automatic tranmission equipped cars made from the 50's up to the 80's would move. :toothless Nothing's locking at low speed. It's a fluid coupling at that point between the engine and transmission. Click here for a really really good explanation of what's going on.

but from a dead stop theres a lot of intial slippage and shuddering, i assumed TC
That sounds like a slipping clutch pack, but first gear is pretty rare to have a slippage and/or shudder, simply because you have the greatest mechanical advantage in first. It's possible that the torque converter clutch is locking and unlocking at low speed like that, but it'd take more testing to see what's really going on.

another question does that 628 mean that high speed TC lock up like what your saying, or does it mean low speed taking off problems etc.
628 just means that there's a converter clutch error. Simply put, the axle speed isn't what it's supposed to be when the PCM is commanding converter clutch lockup. In other words, it's programmed to compare the rear axle speed and engine RPM, and to report this troublecode if something's not right. The converter clutch shouldn't be locking until ~30mph, and usually in 3rd gear. All that the converter lockup does is act like a manual transmission's clutch, matching engine speed to transmission input shaft speed one-for-one, mechanically connecting them, saving gas, wear and tear, and minimizing heat.

i will have to check my mph's and shifts and get back w/ you
Schweeet. :D

Dunno if this helps any, but I determined my torque converter clutch to be bad with the help of a little math and a DVOM. I calculated the theoretical vehicle speed in each gear from 1200 to 3500 rpm, tabulating them in a notebook. Of course, those speeds assume lock-up is occurring, because it's fairly difficult to calculate vehicle speed with a slipping torque converter (which is what almost all of those pre-80's converters did, btw). Then, I tapped into the vehicle harness to monitor voltage on the TCC line with the DVOM and a wire extension with a needle soldered onto the end, while driving down the road. Whenever the voltage dropped to zero, the EEC was trying to initiate lock-up. The calculated speeds were WAY off once it was in OD, indicating massive slippage. The EEC was indeed trying to initiate lock-up, but after trying for a few seconds, would just give up. When I changed the converter, the front was blued, and the cause of the failure was the stator shaft seal.
 
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