Trans is bad, upgrade same time as replacement?

[Smrobs]

Hello all,

New member here. Forgive me and please be patient as I don't know a whole lot about transmissions except when they are working..... And when they're not.

I know this is a diesel forum, but since it's an allison tranny, I figure y'all can answer even though my truck is a gas motor. Alas, I don't have all the specs on the truck, it's my dad's and I'm not able to get the info right now.

I'm mostly just looking at hypotheticals right now anyway and Google isn't being much help beyond directing me here.

Okay, so I've got an '01 silverado 3500, gas, with the Allison transmission.... Farm truck. About 140K hard miles.

Transmission is currently going out and will need to be replaced/rebuilt this winter when we have time and money.

My biggest question is, is it possible to just replace a 5 speed with a 6 speed since it needs replaced anyway or will I just need to do the rebuild/replace and then do the upgrade separately?

Thanks for your time and I appreciate any suggestions/advice.

 

[2004LB7]

there is a lot of threads on converting a 5 to a 6 speed. it's hard to justify for most. just putting a 6 speed in place of a 5 is not going to happen as the TCM and communications are all different.

I'd just rebuild what you have

 

[OleBlackyLBZ]

Hello all,

New member here. Forgive me and please be patient as I don't know a whole lot about transmissions except when they are working..... And when they're not.

I know this is a diesel forum, but since it's an allison tranny, I figure y'all can answer even though my truck is a gas motor. Alas, I don't have all the specs on the truck, it's my dad's and I'm not able to get the info right now.

I'm mostly just looking at hypotheticals right now anyway and Google isn't being much help beyond directing me here.

Okay, so I've got an '01 silverado 3500, gas, with the Allison transmission.... Farm truck. About 140K hard miles.

Transmission is currently going out and will need to be replaced/rebuilt this winter when we have time and money.

My biggest question is, is it possible to just replace a 5 speed with a 6 speed since it needs replaced anyway or will I just need to do the rebuild/replace and then do the upgrade separately?

Thanks for your time and I appreciate any suggestions/advice.

I'm assuming that's an 8.1L gas engine... I don't think that engine will have enough torque to lug that thing around at 1500-1600 rpms anyways. With that engine I would actually prefer the 5 speed I think, seems much better suited to me.

 

[DAVe3283]

The 6-speed uses a different NSBU (gear selector) switch, valve body & harness, etc. So you can't plug a 6-speed in to your 2001 truck.

You can convert a 5-speed into a 6-speed with a modified valve body and custom programming, but I don't know if anyone has done it on the gas engine, so it effectively might not be possible. As cool as it sounds, it is probably not worth the headache of being the first person to try and make it work.

Simpler and cheaper to just rebuild your current 5-speed for whatever power target you have in mind, and call it a day.

 

[Smrobs]

Thanks so much, y'all. That's exactly what I needed to know.

I really appreciate the help. ☺

 

[1FastBrick]

On a 2003 and newer 8.1L you can swap to a 6 speed. You need all the parts from an 06-07 classic 8.1L truck and you have to run an 06-07 operating system on Engine side for it to work.

IMO its just not worth the hassle.