Transmission Help

Thanks to those who replied to my last thread, I've got my eye on a TH400/Dana 20 combo at my local salvage yard. I'm not completely set on that setup though. I would appreciate some input. Working with a 225 Dauntless V6 in a '66 Commando.

A 700R4 is really appealing. I want a good setup that is gets me decent fuel efficiency and can be sourced relatively easy and cheap. That may be asking too much. I don't care to pay for an adapter if I have to, I figure that it will ultimately pay for itself. But I'd love a less expensive alternative. And I really want an automatic over a manual, for ease of daily driving and because I'm 6'6" and leg room is appreciated. (Low gears can be annoying.) This is going to be a daily driver, not a trail toy.

700R4/Dana 300 combo or even Dana 20? JB Conversions has an adapter for the 300.
www.jbconversions.com/products/adapters/1001.php
The OD of the 700r4 is what's hooked me.
How difficult would it be to just modify a factory 700R4/NP208 adapter to the Dana 300? I know all six holes won't align.
What about a 200R4/Divorced Dana 20? I can get a divorced dana setup from an early 70's 4x4 Datsun or Toyota truck.
Or does the 225 do well enough behind a TH350/400 that I'm overcomplicating things. What do you guys average on mpg with the 350/400?
If you all have any suggestions throw them my way!

Thanks!
Elijah

 

Do you have a budget in mind? None of this is likely to be cheap. Are you doing the work? Or paying someone else?

For a daily driver, I can see the appeal of an OD transmission. But just drop a Jeepster Turbo 400\Dana 20 in there and be done with it. Make sure that the Turbo 400 will mate up to the 225 - get the correct Turbo 400 and 225 adapter(if needed). Get both driveshafts at the same time, as the overall drivetrain length will be different. And, I'd get the Turbo 400 rebuilt from the start (if you can afford it)

Also, start thinking about the shifter - stock floor shifter in the console? on the column? Aftermarket shifter on the floor?

A divorced transfer case will require 3 driveshafts. That seems like an expensive, complicated option.

Everything I've read is that the 700r4 TV cable is difficult to adjust correctly. Get it wrong, and you'll burn up your transmission. The 4L60e is an updated version of the 700r4, and would be a good option. But adapting it to a 225 sounds expensive, and you'll also need an expensive electronic transmission controller.

Longer term (or now, if you desire), you might want to consider an LS engine swap with a matching OD transmission. The efficiency and performance of the LS engines is impressive. It's also not a cheap swap. But for a long term daily driver, it would probably be worth it. Don't forget about axle swaps if you are putting a big V8 in there. The stock Dana 27\30 axles that you you still have probably wouldn't last long behind an LS.

 

X2 on the 400 turbo. They are almost bullet proof.

 

Well in light of popular opinion, I think I'll just do the th400/dana 20. However a Warn 25% OD unit might be in the mix.
Thanks for all the input!

 

If it is from a Buick motor it is a direct bolt up. If it is hooked to an AMC boat anchor then you will need to find the Buick adapter ring which is getting pretty scarce.

 

You'd have to use an 18 tcase to use the overdrive.

 

Better to leave the overdrive off. The 18 was cutting edge when it was conceived, but it was noisey and the dana 20 is much quieter. It would be a step backwards to go back to the 18.
The overdrive was conceived to get the 4 cylinder to where it would keep up with traffic because it was underpowered, by modern standards.

 

Do not get it wrong about the dana 18, i have 2 jeeps, with it in them. I still love them for off-road because the 18 has a lower ratio, combined with 427 gears that gives it better manners offroad.

 

There exist TH400s from AMC Jeeps that have one-piece cases (ca '74-79). Most got the Quadratrac, but there were a few with the Dana 20. The only chance for adapting to the Buick engine is using a transmission from a Buick car, or the nailhead transmission and adapter from another Commando or a Buick 350 J-truck or Wagoneer. I would be concerned about availability of flywheels and torque convertors for the nailhead combo. Maybe it's ok - I would look at parts availability first though.

JMO - I'd suggest you pick the transmission that is actually optimal, and just buy the adapter that you'll need. IMO there's no reason to go with the TH350 when you can just as easily use a TH700R4 from a Buick, Olds, Pontiac or Cadillac (any but Chevy), with the opportunity to use the Dana 300 transfer case rather than the inferior Dana 20.

What rear axle does your Commando have? I think a '66 has a good chance of having a Dana 30 rear axle, which is a good target for upgrade. I would look for some 4.27:1 axles from a '72-75 CJ-5, and use them with the overdrive TH700R4.

There are other junkyard possibilities. From '80 on, the CJ-7 was offered with the TF999 and Dana 300. The pattern is wrong for your 225, but I expect you could swap in a Chrysler case and run the 3.9L Chrysler V6, which is essentially 3/4 of a Dodge 318 engine.

 

Well as of now I'm rebuilding my 225. It only has 42,000 original miles on it and really only needed a valve job. I'm keeping the 225 setup, may not be the best engine to put back in it, but its what belongs in it. I've got a th400 with dana 20 lined up to buy that came out of a J4000 with a Buick 350. From my calculations I should be able to go about 63mph @2500rpm on 32" (31.5") tires running my current 3.73 axles at 1:1. Its got a Dana 27AF in the front and its been upgraded to a Dana 44 in the rear. Thinking about swapping the 27 for a 30 with disc brakes. Pulled the power steering box from a 73' with hopes of upgrading, but I don't think it will bolt up to my frame. I made sure to get the bracket with it too, oh well.

 

It's easier to use a PS bracket from a 1971 Jeepster for your Saginaw conversion. You will still need to drill the frame and strengthen it. I may have a mount laying around if your interested. I can also send photos of the box mounted.