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6L90 trans opinions

73K5BlazerSS

73K5BlazerSS

1/2 ton status
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How have you guys made out with your 6L90 transmissions? I keep hearing everyone say they are proven and indestructible. Well maybe not indestructible, but rarely do I hear about others problems with them. I know some use these trucks to drive to the office, although I'm sure more of them are used for hard work.
I'm on my 4th trans in 220k miles. My truck is a 2011 sierra 3500 DRW service body that weighs about 10k lbs on average. The truck has been great other than the trans. I think I've only replaced brakes, tires, and 1 radiator in 220k miles besides the transmissions of course.
I'm gonna get a newer truck soon but I'm afraid of the 6L90. I may wait for the new 10 speed, although I'm sure that will have its problems as well. Does anyone else feel like transmissions are the weak link in these new trucks?
 
They will go out in 200,000 to 250,000 miles if you baby them. Sooner if you actually tow with it or it weighs a lot like a service truck. The last good non Allison GM put in anything was the 4L80E.
 
It's funny you say that my 2006 sierra 1500 has a 4l60e. When my 2011 was having the trans replaced several times I would use that. One time I had to remove material from a job with a trailer. When I got to the scrap yard the trailer and material weighed in at 11k lbs. That was not a good idea at all. I had to leave so much room in front of me to stop. I would never do that again. I was sure that trans would fail shortly after... its still going strong.
I wish the new gas trucks would get an allison trans.
 
The weak link in all of the 6l transmissions is the torque converter. It starts to fail and sends metal though the pump which in turn causes low line pressure which causes the clutches to slip,once that happens its a one way trip to the shop.
The solution seems to be an aftermarket billet torque converter. After that they just keep going.
Overall it's a good transmission but the HD gas trucks getting the 10L1000 next year is going to be a game changer,that transmission is a beast.
 
One of the biggest issues with the 6L90 is the stupid thermostat GM put in the cooler circuit, we had two fail in shop trucks at work. If you watched the temps on the road it was nothing to see 208-220 just driving with no load or towing. Did the thermostat delete on both when we installed the new trannys and both have been fine since. I agree about the torque converter as well as that’s how both of them started..shuddering and then slipping. I think the biggest issue in general is all the extra heat.
 
jake 03 said:
The weak link in all of the 6l transmissions is the torque converter. It starts to fail and sends metal though the pump which in turn causes low line pressure which causes the clutches to slip,once that happens its a one way trip to the shop.
The solution seems to be an aftermarket billet torque converter. After that they just keep going.
Overall it's a good transmission but the HD gas trucks getting the 10L1000 next year is going to be a game changer,that transmission is a beast.
Click to expand...
Im just curious what kind of experience do you have with the 10L1000? I think they are on the Camaros and CTS-V, also isn't that the same trans that Ford (I believe Ford and GM co-developed) is using in their trucks? I'm praying that it's a reliable trans for heavy trucks.
 
Camaro's and 1/2 ton trucks have the 10L80 which is the 10 speed co-developed with ford. The 10L1000 I suspect is the same as the 10 speed torqueshift ford uses with the powerstroke. It's been pretty good behind the L5P,it should have no issues at all behind a gas engine
 
jake 03 said:
The weak link in all of the 6l transmissions is the torque converter. It starts to fail and sends metal though the pump which in turn causes low line pressure which causes the clutches to slip,once that happens its a one way trip to the shop.
The solution seems to be an aftermarket billet torque converter. After that they just keep going.
Overall it's a good transmission but the HD gas trucks getting the 10L1000 next year is going to be a game changer,that transmission is a beast.
Click to expand...
The internet consensus seems to be to get a tune on the transmission and turn off converter lockup in 1-4th so it only locks in 5th/6th. This is how most 6L80/90s are lasting in performance applications with the stock converter. Speeding up shift times also helps with clutch wear.
 
The more I read it looks like the gas engines will get a 10L90 instead of the 10L1000. I just hope it's better than the 6L90.

Edit- I was wrong. The new gas engine HD trucks will get the same 10L1000 as the diesel trucks.
 
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