Transmission replacement approaches

[JKaechler]

Greetings all

My torque converter is beginning to do shuddery stuff, and i expect it will fail not too far in the future. I figure if i have to pull the trans to replace the TC, I should also swap the trans while im at it. Its got 300K on it, and was rebuilt about 100k ago. I tried the fluid drain/fill and added the transguard red. That helped, but is only a bandaid fix. I know there is hardware damage in there. Unfortunately last summer the truck got flat towed about 50 miles without dropping the driveline. That was NOT good for the trans either. So I think its end-of-life is near.

The Tahoe has a BlackBear tune on it, so the first question is how to transfer the BB Tune to a new TECHM trans brain, or should i swap the TechM into the new trans?

The second question is what TC is the most durable for a daily diver that does some occasional towing. Its a 4wd truck, but i dont use the 4x4 all that often.

The third question is where to buy a good solid reman transmission? I want to do the swap myself, and i have even considered putting a Sonnax Zip Kit into the new trans before i mount it. ( i know that will void the warranty right out of the box).

I can see the prices to buy an ATK trans are not terrible, and i bought an ATK reman engine thru JEGS a few years ago for my other truck, its still going strong.
Lots of the places who sell the 6L80 transmission will only ship to a shop, and i need it to ship to my home.


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One thought on the tuning, i have wanted for a while to get an HP Tuners unit and learn to do my own tuning. If i include the HP unit in the budget for this project, could i clone the tuning from the current trans without using the HP license which i would then use on the new trans going forward?

 

[mikez71]

@NickTransmissions !

If you purchased a tune, it maybe locked.. So you may not be able to read it with HPTuners.
I would contact Blackbear about transferring your custom tune to your new TEHCM.

 

[SpareParts]

BB does not lock the tune.

 

[Joseph Garcia]

If you still have your AutoCal and the tune files that BlackBear provided to you, you can make the swap. Certainly contact @BlackBearPerf before doing so, just to be sure.

Circle D seems to be a favorite TC brand here. Stay with the stock stall RPMs, as it keeps it easily drivable for daily driving.

@NickTransmissions should be able to give you some pointers to quality transmission rebuilders.

 

[NickTransmissions]

Greetings all

My torque converter is beginning to do shuddery stuff, and i expect it will fail not too far in the future. I figure if i have to pull the trans to replace the TC, I should also swap the trans while im at it. Its got 300K on it, and was rebuilt about 100k ago. I tried the fluid drain/fill and added the transguard red. That helped, but is only a bandaid fix. I know there is hardware damage in there. Unfortunately last summer the truck got flat towed about 50 miles without dropping the driveline. That was NOT good for the trans either. So I think its end-of-life is near.

Correct - plan on having your transmission completely rebuilt; acquire an upgraded torque converter from a reputable TC company. The transmission builder should be able to source everything you need, including the torque converter and TEHCM (see below).

The Tahoe has a BlackBear tune on it, so the first question is how to transfer the BB Tune to a new TECHM trans brain, or should i swap the TechM into the new trans?

The second question is what TC is the most durable for a daily diver that does some occasional towing. Its a 4wd truck, but i dont use the 4x4 all that often.

Replace your TEHCM with a new OEM TEHCM from GM...Call your local dealer, ask for 'Parts' then give the last eight digits of your VIN. They will sell you the correct TEHCM for your application. You will then need to have it programmed to your vehicle and tuned as required/desired.

The third question is where to buy a good solid reman transmission? I want to do the swap myself, and i have even considered putting a Sonnax Zip Kit into the new trans before i mount it. ( i know that will void the warranty right out of the box).

There are no competent, reliable reman companies - all cut corners to varying degrees. Find a competent, local builder who will rebuild yours properly and completely.

I can see the prices to buy an ATK trans are not terrible, and i bought an ATK reman engine thru JEGS a few years ago for my other truck, its still going strong.
Lots of the places who sell the 6L80 transmission will only ship to a shop, and i need it to ship to my home.


-----

One thought on the tuning, i have wanted for a while to get an HP Tuners unit and learn to do my own tuning. If i include the HP unit in the budget for this project, could i clone the tuning from the current trans without using the HP license which i would then use on the new trans going forward?

I believe that is how many tuners program the new TEHCMs - they download the current programming version from the existing TEHCM while the transmission is still in the vehicle then upload the program to the new TEHCM. Once the base OS version has been uploaded, any other parameters requiring adjustment are performed by the tuner at that time.

 

[15burban]

Lots of the places who sell the 6L80 transmission will only ship to a shop, and i need it to ship to my home.

If by a shop they mean business address. One option is if they ship ups or FedEx is to have them ship it to a "hub" or whatever they're called for that shipping company close to you. Then you just go there and pick it up. I've done it and could have gotten my parts a month earlier if I would have known you could just pick it up at one of their locations. Best part is they have forklifts there to load it into your rig. When you get home and have to unload that's on you lol.

 

[Dustin Jackson]

@15burban Thats good info. If you have an engine hoist at home you can order all kinds of freight without having a business or loading bay.

 

[JKaechler]

There are no competent, reliable reman companies - all cut corners to varying degrees. Find a competent, local builder who will rebuild yours properly and completely.

That right there is the problem. The guy who did my previous rebuild kept the truck for 6 months to do a rebuild. that is unacceptable. other shops in the area all have a reputation of selling you on good parts and later you find out that they too cut corners and put in cheap stuff, or only replaced things that were actually bad.

I dont trust any of them. I did call a couple places and got quotes of 6500$ or 7000$ to bring it in a do a rebuild.
no thank you.


at that price tag, and given the things i am hearing from other local people i would rather take my chances with a unit and installing it myself. I am a perfectly capable mechanic, and i make my living working on computer equipment, the TECHM does not faze me.
The only problem i see coming is the need for that initial program. but if i can use the HP Tuners device to copy the existing program and upload it into the new TECHM, then i am golden.

GIven the behavior i suspect the TCC solenoid may be part of the problem. it does not want to come out of gear as i roll up to a light. it seems to fight me. and my OBD reader can see what seems to be to much TCC slip even sitting at idle. Like the TCC is engaged all the time.

 

[NickTransmissions]

That right there is the problem. The guy who did my previous rebuild kept the truck for 6 months to do a rebuild. that is unacceptable. other shops in the area all have a reputation of selling you on good parts and later you find out that they too cut corners and put in cheap stuff, or only replaced things that were actually bad.

I dont trust any of them. I did call a couple places and got quotes of 6500$ or 7000$ to bring it in a do a rebuild.
no thank you.


at that price tag, and given the things i am hearing from other local people i would rather take my chances with a unit and installing it myself. I am a perfectly capable mechanic, and i make my living working on computer equipment, the TECHM does not faze me.
The only problem i see coming is the need for that initial program. but if i can use the HP Tuners device to copy the existing program and upload it into the new TECHM, then i am golden.

GIven the behavior i suspect the TCC solenoid may be part of the problem. it does not want to come out of gear as i roll up to a light. it seems to fight me. and my OBD reader can see what seems to be to much TCC slip even sitting at idle. Like the TCC is engaged all the time.

Where are you located?

If the tcc solenoid (p0741) is at issue, the TEHCM is bad. Note that that is relatively rare. More often than not, the valve body or torque converter itself is the problem.

Unfortunately, there arent many builders who do a thorough job; those who do arent cheap. I bench build 6L80s and 90s for north of $4,500+ hard parts but everything that needs to get done, gets done so it's GTG for years to come.

 

[JKaechler]

well, there are no codes being shown. No error messages at all in fact. the symptom is that as i coast up to a light or sit in drive stopped with my foot on the brake, it shudders. the closeest thing i can describe it as when i used to have a stick and i would be riding the clutch while holding the brake as well. 'power braking' to try and do a burnout. imagine how good that was for my clutch.


I tinkering with the EFI Live software just now i discovered that i can use it to view the TCC status realtime. so tomorow i will hook it up and drive it. i should see the TCC released when my foot is off the gas and i am at low speeds. (if i dont, then that explains the behavior)
I suspect that what i want to get is the TCC not to lock up until i am at highway speed. but up around 55mph and higher i do want there to be some amount of engine braking available. i see several videos and posts on how to achieve that with the HP Tuner, but i dont think the EFI live device i have can do that.

 

[NickTransmissions]

well, there are no codes being shown. No error messages at all in fact. the symptom is that as i coast up to a light or sit in drive stopped with my foot on the brake, it shudders.

converter limit valve in the pump is heavily worn (detectable via vacuum testing) or TC is coming apart on the inside.

What state are you in?

 

[JKaechler]

What state are you in?

I am in Central TExas, Near Waco

 

[NickTransmissions]

I am in Central TExas, Near Waco

I may know of a shop in that general area - will check and get back to you.

You can also purchase a programming subscription for your vehicle via AC Delco's Technical Delivery Service.

 

[mikez71]

TCC slip wll still show RPM difference even with TCC disengaged, so I wouldn't worry about the slip reading at idle.

EFILive should do most, if not all, that HPTuners can.. I believe...

Replace motor/trans mounts yet?

 

[JKaechler]

Replace motor/trans mounts yet?

I have not, as they dont seem to be at issue.

 

[tom3]

Was the torque converter replaced with the transmission? Was it possible to put an improved TC in it then?

 

[Chris2144]

For what it’s worth I just bought an 07 Denali it had a shuddering converter at about 45-50 under light throttle it would shudder and while I was watching everything with hp tuners I could see the tcc slip jumping around matching the shuddering feeling. Line pressures were good and shifts were good no codes so I decided to put a converter in it.
This was the original trans with 160k on it. So far it has completely fixed the problem new filter and cleaned everything. I used the new luk torcon torque converter. It can be had from many different vendors for around 450.00

Hp tuners can read and write new tune files and as long as black bear didn’t lock the tune you are good to go. Be aware that you will have to buy the device plus pay for credits I believe you will need 2credits for that vehicle 50.00 a pop.

Also note that hp tuners does not support emissions altering so things like o2 and egr delete will have to be done via user defined parameters.

 

[alpha_omega]

other shops in the area all have a reputation of selling you on good parts and later you find out that they too cut corners and put in cheap stuff, or only replaced things that were actually bad.

I hear you on shops cutting corners. The nightmare I just dealt with on my ‘11 Denali was painful to say the least.

I dont trust any of them. I did call a couple places and got quotes of 6500$ or 7000$ to bring it in a do a rebuild.

That’s about normal for some locations, TX being one of them. That cost would be everything high end and done right. At least it should be.

After the issue I had, I’m ready to pull a stunt like @NickTransmissions did - buy my own transmission tools and then teach myself the 4L60 & 6L80. At least if I mess something up, I’ll only have myself to blame. And for the cost of the repair job, I’ll have my own tools.
I just need a heated shop, cuz it’s going from 61° down to 13° overnight here in Michigan. Tomorrow is going to be nasty when all this rain freezes.

 

[strutaeng]

@JKaechler Didn't know you were near Waco...

I asked around a few years on PT.net for a reputable shop for a former coworker's 6L80 on his 2017 Silverado. Phoenix Transmissions in Weatherford is what was recommended. My buddy towed his truck there and got it rebuilt by them. This was like 3-4 years ago and I believe it was around $5k-ish. I'm sure it's higher now, but he said he was really happy with the rebuild and transmission worked better than when new.

May be a fit far from you though.

Good luck and I hope your issues get resolved.

 

[JKaechler]

Interesting development, i found my paperwork last night from the rebuild in 2023... im still inside the 36 month warranty period! Guess who i am going to go see today.

That rebuild was supposed to include a new TC, and it ran just fine for 2 years. i suspect that something in there just started to degrade. that woven carbon friction ring or something. My hope is that because it has not cratered, all he will need to do is swap the TC and move forward.

If he has to replace the TECHM, i will deal with that afterward. I will head down the HP tuners route after the hardware is fixed.