Allison-style tranny? Help please!

[350xj4x4]

I have been offered part of an allison-style tranny from a friend of mine. If you're not familiar with this style it's one like truckers have (maybe more familiar with the browning tranny) where you can actually have high or low gears for your tranny w/o using the t/c. He said his buddy was asking about $300 for it but it's not actually the whole transmission. It's just the part that mounts on the back that makes it any tranny that style. Anyone have any know-how on the matter? I'd like some help because I don't know anything about it. Thanks in advance
~Charlie

 

[5-90]

So, you're not necessarily getting the Alison tranny - you're getting a box like a Saturn or Klune-V overdrive/underdrive. It's a gear splitter that effectively splits all of your gears in two.

Overdrives are used for vehicles with low gearing, to allow higher speeds - it's like running every single gear range through an overdrive range. Most overdrive boxes, I think, will give you a 20-40% overdrive (GR .80-.60:1)

An Underdrive does just the opposite - for higher gears, it gives you a lower option. An Underdrive ratio is usually more like 1.5-2.0:1

I'd take it, if it can bolt between your transmission and your transfer case. If you really want something like that and his won't work, check both Saturn's and Klune's sites (a googling will turn them up) and see what they've got.

5-90

 

[350xj4x4]

So, you're not necessarily getting the Alison tranny - you're getting a box like a Saturn or Klune-V overdrive/underdrive. It's a gear splitter that effectively splits all of your gears in two.

Overdrives are used for vehicles with low gearing, to allow higher speeds - it's like running every single gear range through an overdrive range. Most overdrive boxes, I think, will give you a 20-40% overdrive (GR .80-.60:1)

An Underdrive does just the opposite - for higher gears, it gives you a lower option. An Underdrive ratio is usually more like 1.5-2.0:1

I'd take it, if it can bolt between your transmission and your transfer case. If you really want something like that and his won't work, check both Saturn's and Klune's sites (a googling will turn them up) and see what they've got.

5-90

That sounds like just what he was talking about. Thanks a lot 5-90! I just did the search and it gave me such a better idea of what I'm looking at. That's so awesome. I'm so looking forward to this! $300 a good price?

 

[5-90]

If it fits and you don't have to do a lot of work, I don't see a problem. Most of those over/under boxes seem pretty spendy as I recall - but I haven't checked lately. Did you look around? What prices did you see?

The nice thing about an overdrive box is that it would allow you to run much deeper gears on the street - the overdrive will help make up for that. I'd have to crunch some numbers and figure out what you're thinking, but it's pretty safe to say that (assuming stock-31" tyres or so) that you'd be able to net an effective cruising speed, at the crankshaft, with gears in the high fives, rather than sticking to 4.10/4.56 or so. Useful if you crawl a lot, and also good if you tow (since you can shift in and out of your gear splitter "live" - how do you think semi trucks work?)

I'd not mind having one when I overhaul my 88, since it seems like I'm always pulling something and I'd like to have the deeper gearing.

5-90

 

[350xj4x4]

If it fits and you don't have to do a lot of work, I don't see a problem. Most of those over/under boxes seem pretty spendy as I recall - but I haven't checked lately. Did you look around? What prices did you see?

The nice thing about an overdrive box is that it would allow you to run much deeper gears on the street - the overdrive will help make up for that. I'd have to crunch some numbers and figure out what you're thinking, but it's pretty safe to say that (assuming stock-31" tyres or so) that you'd be able to net an effective cruising speed, at the crankshaft, with gears in the high fives, rather than sticking to 4.10/4.56 or so. Useful if you crawl a lot, and also good if you tow (since you can shift in and out of your gear splitter "live" - how do you think semi trucks work?)

I'd not mind having one when I overhaul my 88, since it seems like I'm always pulling something and I'd like to have the deeper gearing.

5-90

Yeah, we'll just have to wait and see what I'm going to do. I'm going to probably have somewhere between 33 and 35" tires and running a t400 with 1/2 tons from a suburban (83) with an np205. That's all the planning I have right now. I'd really like to get a hold of that splitter, though. Thanks for the info