Transmission replacement approaches

[Joseph Garcia]

If the transmission needs to be rebuilt, have you considered simply buying a new one? I recently did this on my truck, when I installed the supercharger. I did not want to second guess the condition or remaining life of my trans or TC, so I simply replaced them with new.

 

[JKaechler]

i have. but i am not sure about where to buy a 'new one' from. direct from Gm?

 

[89Suburban]

Good stuff there fellas. FWIW, when I did my tune I did it through Diablew. I have all the stock and final tunes stored in the tuning device. I also keep the same copies stored on my laptop. In case I ever have to cross this bridge, I will be able to reinstall the tune.

 

[Joseph Garcia]

i have. but i am not sure about where to buy a 'new one' from. direct from Gm?

Yes, directly from GM with all the latest fixes/improvements included.

 

[Dustin Jackson]

I'd explore the warranty route first. My first transmission lasted 17 years, I'd be a little upset if the next one only lasted 2 !

 

[Chris2144]

Definitely go the warranty route but, when transmissions are rebuilt a lot of builders don’t replace everything. This does lead to decreased lifespan if I’m going to pay good money for someone to rebuild my trans it will be better than new. Glad you’re still in warranty and hope they give you a bunch of crap about it.

 

[kurtibm]

If you decide or are forced to go locally for a builder this article has a pretty good base for the known torque converter issues and upgrades for your T.C. 6L80 Repair Article An important part of the article (to me) is near the end, titled '

Suggestions from the TC Builder to the Trans Builder' ​

 

[fredcook]

My torque converter is beginning to do shuddery stuff,

I may have missed this in the thread, but what diagnostics have you done for this? I ask because all of out three GMT900 Tahoes have done this multiple times over their high mileage lives. The shutter would take place coming to a stop at around 20 MPH as the trans downshifted. But every time it has been a simple matter of cleaning the throttle body. The dirty throttle observation is, if RPM dips slightly when it shudders (with brakes applied), it's usually a dirty throttle body. If it shudders coasting down through 20 MPH without applying the brakes, then it's more likely the trans or converter.

Again, if I missed it and this has already been covered, ignore me. Have you diagnosed with a bidirectional scan tool? You can use a scan tool to manipulate the TCC solenoid with in the TCM. Disable the TCC and test a coasting stop. If the shudder shudder goes away, then it's the TCC. It's probably glazed over (assuming it's not just bad fluid). If it still shudders, then it can be either the trans (accumulator) or engine related. Do some live data streams (PIDs). I check TCC slip speed as I slow down. A good number has been under 20 RPM during the shudder window. If it jumps around above 20, the converter is having issues. Also check live data misfires. Even if you don't get any misfire DTC's, you may still have them. I've seen this myself... several misfires on a specific cylinder as the shudder happens during the downshift. Replacing the plug resolved the 20 MPG shudder. Another test I've done is use the scan tool to force the trans to remain in second to keep it from dropping to first. If the shudder goes away, then it points to the accumulator.

Test driving can be difficult when trying to capture live data streams. I use a TopDon Phoenix Plus 2, and set up a screen that includes RPM and speed along wit the PIDs mentioned above. Then I just hit record and test drive. The Plus 2 is great for this since it can display 12 live data graphs at a time.

BTW, I am NOT a professional mechanic. Just a DIYer / enthusiast / hobbyist since the 1970's. I'm just throwing out suggestions.