Anyone running an 8.1, what trans are you using?

Am in the process of rounding up parts and pieces for my 1982 dually. For anyone running an 8.1 what trans are you using? Only plan a cam swap on my motor so not a serious build.

Have a 2003 Suburban with the 8.1 so planning to swap that in. Unfortunately it's a 4x4 so can't use the 4L85e unless I have it converted to RWD. Also, don't think the 4L80e will handle the HP and torque in stock form.

Had a 2001 2500HD with an 8.1 and the Allison and it was great. All I read on here says it won't fit without a body lift though.

The 1000 Allison would be my choice or stick shift. You can find them in some motorhome units.

When I saw 8.1 was thinking Detroit lol
The 8.1 gassers are cool too, I'd build one!

I have a few 4l80e, and retrofitted it to my 454 with an adapter from Advanced Adapters. Mine was a two wheel drive trans so I can run my speedo from the trans instead of the 205 (73) which does not have any of that stuff. tale shaft comes off and the AD goes on. Also the adapter comes with the input shaft with the big bearing for the205, which must be machined for the bigger bearing. I could get pic, stuff is up in the shop.

I know of two 8.1 swaps, one is running an Allison (4wd truck) that my tuner buddy tuned for him. And a coworker of mine is running a 4L80 in a 2wd. An 80 ought to handle the torque just fine, or at least it would with some minor upgrades

Holdener has a few tests with the 8.1, the ZZ502 cam swap on a junkyard motor got 464 HP, 582 TQ. Most of what I read a stock 4L80e is good for around 440 TQ, 4L85e says 460 which is just over the 455 the 8.1 was rated at.

I had a 2007.5 Dmax with the 6 speed Allison and it was great. Would like to go that route if there's not a lot of hacking up the floor to make it fit. Also looks like going from 4x4 to RWD is pretty easy, don't have to strip the trans down.

Also, as far as I know the Allison was only in the HD or chassis cabs where the body mounted higher on the GMT800 series trucks. So you will have to make more room for it. (Can you say body lift?)

IDtag said:

Holdener has a few tests with the 8.1, the ZZ502 cam swap on a junkyard motor got 464 HP, 582 TQ. Most of what I read a stock 4L80e is good for around 440 TQ, 4L85e says 460 which is just over the 455 the 8.1 was rated at.

I had a 2007.5 Dmax with the 6 speed Allison and it was great. Would like to go that route if there's not a lot of hacking up the floor to make it fit. Also looks like going from 4x4 to RWD is pretty easy, don't have to strip the trans down.

Click to expand...

A 4L80, even in completely stock form, should have no problem at 582TQ. Unless you are drag race launching it or pulling very heavy loads, it will be just fine. You only need to change the output shaft, rear lube plug, and add a tailhousing to convert the 4wd to 2wd.

Bextreme04 said:

A 4L80, even in completely stock form, should have no problem at 582TQ. Unless you are drag race launching it or pulling very heavy loads, it will be just fine. You only need to change the output shaft, rear lube plug, and add a tailhousing to convert the 4wd to 2wd.

Click to expand...

Converting a 4WD 4L80 to 2WD requires complete disassembly of the transmission, including swapping the 4WD output shaft for a 2WD and adding the OSS reluctor gear pick up to the output carrier (91-93 4WD 4L80Es had these from the factory but 94+ omitted it).

I'm running a tried and true SM465 behind a old school 8.1

A used 4L80 a good valve body kit will easily handle far more than the 8.1 will produce.

I like those valve covers. I'm getting lazy in my old age, like the automatic unless it's a just for fun car.

NickTransmissions said:

Converting a 4WD 4L80 to 2WD requires complete disassembly of the transmission, including swapping the 4WD output shaft for a 2WD and adding the OSS reluctor gear pick up to the output carrier (91-93 4WD 4L80Es had these from the factory but 94+ omitted it).

Click to expand...

You definitely need to disassemble it to get to the shaft to replace it, but it may or may not have the reluctor gear on it all the way up to 97. Its super easy to just pop it on when you have it out though. I think it was only ~$15 for a brand new reluctor gear and it took me 10 minutes to just heat it up in my oven and drop it on. I got a good condition used 2wd output shaft from Global transmissions for $10 to cut down for my 4L80.

I would pull it apart for an inspection, dual feed, Sonnex LB1 valve, and rollerize output with no-walk bushing anyways before putting it in the truck if I was him, so changing it to 2wd at that point is pretty basic.

Did come across a 2wd trans out of a 2007 with 80k on it. If minor updates will keep it alive seems like a much easier and cheaper route to go.

Bextreme04 said:

You definitely need to disassemble it to get to the shaft to replace it, but it may or may not have the reluctor gear on it all the way up to 97. Its super easy to just pop it on when you have it out though. I think it was only ~$15 for a brand new reluctor gear and it took me 10 minutes to just heat it up in my oven and drop it on. I got a good condition used 2wd output shaft from Global transmissions for $10 to cut down for my 4L80.

I would pull it apart for an inspection, dual feed, Sonnex LB1 valve, and rollerize output with no-walk bushing anyways before putting it in the truck if I was him, so changing it to 2wd at that point is pretty basic.

Click to expand...

Yep, heating or a hammer/drift punch will install it quick...easy deal.

I just didn't want anyone to think it was a matter of just popping off the ext housing and r/r just the output shaft without taking the transmission apart (Ford 5R110s and Allisons are convertible by just removing the back sections; unfortunately the GM transmissions aren't quite as easy to convert)

Yep, dual feed direct clutch
rollerize rear output
no-walk bushing
Sonnax Boost and Line to lube PR valve in pump
Lube mods to the stator, body, OD roller feed, center support, etc
Sonnax TCC valve, 1-2/2-3 shift springs and bore plugs (95+ only on the Sonnax bore plugs as the design changed starting in 95)
Drill the spacer plate per stall speed, vehicle weight, cam grind, desired shift firmness

Replace all electrical stuff as the harnesses are notorious for leaking at the connector and/or shorting out...