A good portion of TH425 parts are shared with a TH400.
4T80 reliability and 06+ Northstar?
- Thread starter redhat
- Start date
A TH400 may be my next adventure, just in learning it more. I’ve been linking people to posts of yours from years ago and they have helped out a TON of people. I’ve even built a few performance 4L80E’s for some local guys based on the knowledge you and others have shared with me over the years! Thank you again sir for all that you do and all that you have contributed to the community!
I've had 4 different 4T80 equipped vehicles, and I've had one torn apart. They are STOUT.
The biggest issue they had was early on, an internal valve body screen would get forced out and snap the shift solenoids. The issue was fixed post-'95ish. TCC issues do happen, but more from lack of maintenance. A lot of these units get serviced by people that don't know the 4T80's have a second drain plug INSIDE the case that you remove after the pan comes off. There's another 4-5 quarts of fluid held in the side case that needs to be drained. The internal filter is also not serviceable without dropping the transmission at least partially.
The biggest issue they had was early on, an internal valve body screen would get forced out and snap the shift solenoids. The issue was fixed post-'95ish. TCC issues do happen, but more from lack of maintenance. A lot of these units get serviced by people that don't know the 4T80's have a second drain plug INSIDE the case that you remove after the pan comes off. There's another 4-5 quarts of fluid held in the side case that needs to be drained. The internal filter is also not serviceable without dropping the transmission at least partially.
As far as I know, most of the TCC problems are solenoid related, not hard parts. And unfortunately, the solenoid lives in the side cover. Not ideal when stuffed in a FWD car.
Not sure TCC problems are as much of a function of maintenance as it is blind luck.
Not sure TCC problems are as much of a function of maintenance as it is blind luck.
- Joined
- Mar 19, 2022
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- 671
TCC issues are lack of maint, but more importantly (I believe) programming. Locking up the TCC in almost every gear and unlocking while simultaneously shifting and relocking asap shifting. When computers are in control of timing, throttle, line pressure, shift solenoids, and TCC. There is a lot of freedom in how things shift. But short shifting and TCC modulation 1,000 times every few miles is crazy to me. All in the name of CAFE.
