I've got a '79 CJ-5 with the original 258, bone stock with the excecption of a weber carb and a header, rear driveshaft with CV joints, the T-150 3 speed and the Dana 20 transfer case. It is my daily driver, so I would really like to put an overdrive gear in it to make it more highway friendly. Is there a transmission swap that I can do that will bolt up relatively easily without going to an automatic? Or would I be better off going with something like a Saturn Overdrive unit? Either way I'm afraid that the rear drive-shaft angle is going to be too much. Any help would be greatly appreciated.

   Jack  

nv3550  

Your biggest hurdle is the Dana 20. It is a strong box but has too high of low gear, the bolt pattern between the trans and tc is unique and it has a passenger side drop.

So in order to reatin the Dana 20 it will require an adapter. They do exist from both Novak and Advanced Adapters, but they cost five hundred dollars.

It would be nice to be able to swap both the trans and tc as a matched setup. That would give you OD in the trans, a lower lo-gear and save you the need for an adapter. But, a lot of the options would include a driver side drop. So, that makes it limiting.

The NV3550 is an ok choice and is strong enough but is not very nice in terms of shifting and it is noisy.

If the price were right maybe.

My choice would be an AX15. Much smother shifting and much quiter.

Both will require a $500 adapter for the Dana 20.

I would rather spend the $500 on a Dana 300. It has a 2.62 low vs the 2.0 low in the Dana 20. The Dana 300 will require a clocking ring for the Nv3550/AX15 but that is only $100.

So, if you could find a Dana 300 for under $400, you'd be money and gearing ahead.  

good point!  

So an AX15/ Dana 300 combo, if I could find one, would be a good choice. What about the over-all length? Would the length of the AX15 give me problems with my rear driveshaft angle?  

A T5/300 combo comes in the 80's CJ5. The AX15 is 1" longer than the T5. The 300 is 1" longer than the Dana 20. The AX15 is 2" longer than the T150.

So, a rough estimate would be that the rear drive shaft would be 3" shorter. That is probably enough to warrant a new rear drive shaft. Call Tom Woods, 4XShaft.com, and ask them for recomendations. They will be very helpful.

In case you're wondering, the T5 5spd is a light duty transmission with not a very good track record.