390 with Allison Tranny

[mrtleavitt]

Ok, I came across a Allison Transmission out of a 2008 GMC Sierra 2500HD. Has anybody seen any info about swapping something like this to an FE? I think this would be a sweet upgrade to my F100. 6 speed auto would be hard to beat!

[averagef250]

The 1000 and 2000 series Allisons are pretty good trannies, but they are fully electronic. They have a removeably bellhousing and can be had in SAE3 or GM bellhousing patterns To mate an Allison to an FE you could use one of the adapters out there that converts the back of the block to chevy pattern with a special flexplate. You might be able to use an FT SAE3 adapter with an industrial Allison. I know if you have an engine that's set up with an Allison 54X series you can bolt up a 1000/2000 without changing a thing.

The problem with the Allison is controlling it. The stock computer that controls the Allison is stand alone in medium duty and GM applications. You can use the stock computer, but the shiftpoints will not be right. Scott at Destroked just recently managed to crack the Allison operating code and has come up with an auxiliary box that plugs between the stock computer and the tranny to modify shift points and performance.

One of the biggest things that Scott's box does in addition to allowing you to program your shiftpoints is it eliminates the requirement to defuel the engine on full throttle shifts. To protect the tranny the computer forces the engine to partially defuel for a split second while it shifts. This sucked for diesel guys since defueling at shift time hurts spooling big time with larger turbos.

The Allison 5 and 6 speed 1000 and 2000's are all the same transmission. The 6 speed just uses a different computer and has a factory installed transgo shift kit.

Used Allisons are $500-$1000, but the rest of the parts to control it and mate to an FE will require a mortgage or sale of a kidney.

The Allisons are tough though. With stock programming they hold up fine to 700+ lb/ft. With the right programming they're said to take 1500 lb/ft.

[ares360]

if you do this, make sure you post pics and updates. This would be an awesome project, Go For IT!

[papabug71]

Yup, my auto Dodge did the de-fueling crap at WOT. Thats why I traded that baby in on a NV5600 6 speed equipped Dodge!!!!

Chrysler calls it "torque managment".

[averagef250]

The dodge diesel autos are pretty good built right with a good converter. I'd take one over an Allison anyday myself. From what I hear the Allisons are a rebuilders nightmare. They have lots of quirks and are not worth the hassle to work on unless you really, really know what you're doing.

If I had a newer dodge with a 47/48RE I'd spend $100 on the parts to convert it to a 47RH. The 94-95 RH autos are non-electronic and bulletproof with a shiftkit, steel planets and a 48RE overdrive section.