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8 speed transmission rebuild

MN6.2

By MN6.2
in Engines & Drivetrain

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MN6.2 Enthusiast

MN6.2

Posted
Posted

Just curious if anyone has had the time/money to rebuild one of these. Truck has 125,000 miles and counting. I Love the truck. t's a 2015 max trailering package 6.2l tuned on e85 and fun to drive but as everyone knows the transmission does it's clunky weird stuff all the time although it does not have the shudder. I just don't know if rebuilding the trans and a new torque converter will actually cure the weird, clunky nature of the 8l90. Rebuild kits are out there and so are torque converter but they ain't cheap. The truck would be perfect if the transmission was smooth but I don't want to waste my money if a rebuild won't actually help it much. 

papageoff Enthusiast

papageoff

Posted
Posted

I'd reach out to monster transmission. They're an expert in many units and may have the answer you seek.

Sent from my SM-G892A using Tapatalk

MN6.2 Enthusiast

MN6.2

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  • Author
Posted
12 minutes ago, papageoff said:

I'd reach out to monster transmission. They're an expert in many units and may have the answer you seek.

Sent from my SM-G892A using Tapatalk
 

Sounds good I'll look em up.  thank you

lucas287 Enthusiast

lucas287

Posted
Posted

I personally think you just need to tune it. I have HPTuners software and I've made my 8L90 very livable.  Perfect? No. But much improved? Yup. It's not all trans related too. Some of it is due to the driver demand tablets demanding negative torque. That exacerbates things greatly. 

 

Some of the things I've done to help the clunkiness: 

 

Adjust negative torque at low speeds on driver demand tables, I disabled AFM and their corresponding TCC slip modifiers, zeroed out TCC slip in 7th and 8th, completely unlocked the TCC from 1st to 6th, changed the entire part throttle shift schedule, fine tuned downshift speeds, and adjusted the base line pressure during TCC lock in 8th gear.

 

Those changes plus my traction bars make my truck so much more enjoyable to drive.

MN6.2 Enthusiast

MN6.2

Posted
  • Author
Posted
13 hours ago, lucas287 said:

I personally think you just need to tune it. I have HPTuners software and I've made my 8L90 very livable.  Perfect? No. But much improved? Yup. It's not all trans related too. Some of it is due to the driver demand tablets demanding negative torque. That exacerbates things greatly. 

 

Some of the things I've done to help the clunkiness: 

 

 

Adjust negative torque at low speeds on driver demand tables, I disabled AFM and their corresponding TCC slip modifiers, zeroed out TCC slip in 7th and 8th, completely unlocked the TCC from 1st to 6th, changed the entire part throttle shift schedule, fine tuned downshift speeds, and adjusted the base line pressure during TCC lock in 8th gear.

 

Those changes plus my traction bars make my truck so much more enjoyable to drive.

Thanks for that. The truck does currently have a trans tune (and engine tune) from a local gentleman that uses HP tuners. The truck also has AFM disabled. Maybe I will bring this up to my tuner to try and get some specifics to what he did although he is very busy right now. I'm not familiar with how these trucks are tuned at all specifically so I just let him do what's best. Like I said I love the truck and want to keep it but I'd be disappointed for sure if I spent the money for a rebuild and it still did the weird and clunky stuff. Maybe I can get a Circle D TCC first and go from there but even then it would suck if it didn't help. 

Black02Silverado Senior Enthusiast

Black02Silverado

Posted
Posted

If not already done, I would do a complete fluid exchange.  Fresh ATF will always help and it can't hurt.  If you are interested in AMSOIL let me know.  I can get you a quote delivered to your door.

MN6.2 Enthusiast

MN6.2

Posted
  • Author
Posted (edited)
21 minutes ago, Black02Silverado said:

If not already done, I would do a complete fluid exchange.  Fresh ATF will always help and it can't hurt.  If you are interested in AMSOIL let me know.  I can get you a quote delivered to your door.

Thanks. I had it changed when I had the truck in to be tuned. That was about 15,000 miles or so ago. 

Edited by MN6.2
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lucas287 Enthusiast

lucas287

Posted
Posted
7 hours ago, MN6.2 said:

Thanks for that. The truck does currently have a trans tune (and engine tune) from a local gentleman that uses HP tuners. The truck also has AFM disabled. Maybe I will bring this up to my tuner to try and get some specifics to what he did although he is very busy right now. I'm not familiar with how these trucks are tuned at all specifically so I just let him do what's best. Like I said I love the truck and want to keep it but I'd be disappointed for sure if I spent the money for a rebuild and it still did the weird and clunky stuff. Maybe I can get a Circle D TCC first and go from there but even then it would suck if it didn't help. 

I probably wouldn't go circle d route for their 8L90 stuff. General consensus over on hptuners forum is they don't quite have it figured out. 

 

Plus, there's underlying problems at play with aftermarket converters and the 8l90. It's difficult to ACTUALLY command zero slip in this tranny. You can bump the line pressure and command zero and for some reason it slowly decreases pressure until it slips then it slowly applies again. Wash rinse repeat. There's a couple long threads with much more detail about it. 

 

I'm still playing around with my tune but once I have it driving where i like it (subjective i know) i can send you the file for your tuner to have a baseline. 

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