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.

 

[JKaechler]

So, coming back to this after a whole long delay. The Trans tech guy took a look at it and says that the trans itself is fine for now, my oil changes have likely limited how much crap gets into the system as the TC seems to be suffering some kind of issue. I have replaced the throttle body entirely, and using the HP Tuners device (the tune was not locked by the way, i have a lot to learn but the device works) i was able to watch as it comes down to a stop and shudders and downshifts, that the TCC solenoid is NOT commanded to be engaged. So it seems to me that the TC itself is somehow damaged. Even when not commanded to lock, it still has some amount of drag or engagement. When i changed the fluid there was a little bit of crud in the pan but not all that much. The Trans acts just the way it should when accelerating. I was stuck in Dallas traffic a couple weeks ago and that sort of idling forward showed a lot of the shuddery behavior... like the TC does not want to release, even when the TCC solenoid isnt engaged. i can feel that the engine is still coupled to the transmission when it should not be. it feels just like riding the clutch did in my old car.


All this is leading me to the conclusion that i need to swap my TC. sooner rather than later.'
Buying a stall from somebody like Circle D is quite expensive.. around $1k. but all the parts houses sell 'remanufactured' units which i am leery of trusting. is there a middle ground? I found a TC from a company called 'Boss Hogg' but there seem to be no reviews from my fellow wrench benders...

 

[donjetman]

Almost 8 yrs and 78k miles ago I installed a Precision # P4646 (gopnh.com) TC in my 07 Denali 6L80e, cost $218, still going strong with 208k miles on the tranny and vehicle

 

[Fless]

There are a couple of threads about the LUK converter, if that's an option for you.

New luk torcon converter

So I bought this 2007 Yukon Denali with a shuddering converter. It has 161k miles. Has the 6.2 awd 6l80 I replaced the converter with the new luk converter. Tc0017 Was recommended by a shop that it’s the only one they will use for stock replacements now. The install is straightforward no change...

www.tahoeyukonforum.com

Any Experiences with The LuK TorCon TC0017 Torque Converter?

Y'all, In one of Summit's latest mini catalogs, I ran across the Luk TorCon TC0017. Here's a page on the Sonnax site about it, and a page on an industry site about it (yes, these are both clearly marketing). So, does anyone have any experience with this particular converter? Any input on...

www.tahoeyukonforum.com

 

[JKaechler]

I like what I read about the LUK. I like the price tag as well. Do any of you have a recommendation on a transmission jack? last time i did an auto trans swap i used a floor jack and a 2x4. i do not want a repeat of that circus! I will be working on the driveway with the truck up on ramps.

 

[Chris2144]

Harbor freight has real good one for like 200ish bucks. It’s hydraulic and adjustable.
Works great.

They also have a cheaper one it’s ok lifts just fine you have to use a ratchet or an impact to lift and it doesn’t roll as easy but it gets the job done.

 

[kurtibm]

You may consider installing a new rear main seal while the trans is out.