Switching from a Dana 18 to Dana 20

I recently put Scout axles under my Jeep so I'm going to switch to the Dana 20 transfercase to match the centered differential. I have some questions on the swap before I get started.

A little more background: I have a T-90 tranny with a Buick V6 231. I purchased a Dana 20 that came with a T-150 tranny already attached. I'm wondering if I should go ahead and put in both the Dana 20 and the T-150 or just swap in the Dana 20, keeping the T-90? I assume that I would need a different engine to tranny adapter for the T-150 than what's in there now, so that would be a cost factor for me. I don't know if the T-150 is better than the T-90, better enough to spring for the adapter? Will the Dana 20 be a direct bolt up to the T-90? I've read up a on it a little bit, but I'm still not sure what the obstacles are with doing it.

I realize the Dana 20 isn't geared as low as the Dana 18, but I can address that sometime down the road. I just need to get the Jeep back on the road the easiest way possible. Thanks.

 

sorry cant help w/the tec question but how long did it take u to fine the D-20? and how much did u pay if u don't mind me askin?

Thx

 

You can use a T-86 rear bearing retainer on the T-90 to convert it for the large hole case. You remove the rear plate from the T-90 (the recessed removable one) and install the T-86 retainer. Simple and effective. You will need the input gear to match your 20 transfer case. The T-86 retainer is available at most places that deal with vintage Jeep parts, Walck's, R&P, etc. You will need the retainer housing, snap ring, and bearing. Much cheaper and easier than putting in the T-150. Nickmil

 

All that Nick says is true... however, if it were mine, I'd consider using the T-150. Certainly the T-150 is a better and stronger transmission than the T-90. Tremac built the T-150 under license from Ford, and it's a copy of the 3-speed Ford transmission that was used for many years in Ford passenger cars. The T-150 is fully synchromesh in all forward gears, and likely to be in better condition than your T-90. The T-150 was supplied with both the inline 6s and 304 V8s in CJs from 76-79, and has a good reputation.

I'd say a lot depends on the condition of your T-90, and how much you want synchro in 1st gear. The T-150 also has somewhat better gearing than the T-90, and has a seal between the trans and TC, so they do not share oil.

Novak shows an adapter for the T-150 to GM bells, but also has a page on adapting Ford transmissions (sp. the T-18 and T-19) to GM bells without an adapter. The T-150 has a longer stickout than the T-18, and this may require the use of Novak's plate adapter or something similar, but maybe not.

So, not cheaper or easier than the T-86 retainer, but something to consider.

 

I agree with Tim that the T-150 is stronger than the T-90. Shoulda said that in my first post, just not the path of least resistance. If you decide to go with the T-150 R&P modifies a case to bolt to gm bellhousing with no adapter. You just need a Ran 3 speed input or cut off the excess length of the pilot of the T-150 input. The only difference in the inputs is the T-150 pilot is much longer. You will need a modified front bearing retainer as well which R&P, Partsmike probably, Novak, etc. can all supply. You will also need a modified pilot bearing that the above can supply as well. Nickmil

 

Thanks for the input Nick & Tim. Somehow I knew you guys would have some good info for me . I suspected that the T-150 was stronger, but it also sounds like I would be in over my head with that swap.

I think I'll keep the T-90 for now and just get the Dana 20 mounted to it. Sounds like that will get me back on the trail sooner.

Adam- I paid $100 for the tranny and TC. I posted some wanted ads on a few different websites and came up with one locally within a week. The Dana 20s are out there and since it's not a highly desirable tc, you shouldn't be paying an arm and a leg for it. It's just a quick fix for me right now. Ultimately I'd like a tc and tranny with lower gearing.

 

Okay, I've hit my first obstacle with putting the Dana 20 in. The first picture shows what I believe is the bearing retainer for the T90 that I need to replace with the T86 retainer. How do I remove the T90 recessed retainer? The exposed bearing that's on the T90 needs to come off I assume. It's on tight, do I need to use a puller of some type to get it off? The tranny shaft has an inch or so of play in and out. It the normal or have I botch something up?

Sorry, for all the rookie questions, but I was really hoping I could do this work myself, without having to load up the Heep and take it to a shop. Thanks.
View attachment 18269 View attachment 18270

 

You might need a puller to get the bearing off. On the plate, I usually have the shifter top off and punch it out from the inside with a long punch. You can usually drive the bearing off that way too. Be careful though as the output shaft likes to come out with it and drop the front pocket bearings down into the transmission case. Just take your time and watch close. It'll happen. If you can get the bearing off before removing the plate that lessens the chance of the output shaft coming out but can still happen. Nickmil

 

Thanks Nickmil. I was able to get the bearing off with a pitman arm puller and from there, with the top cover off, the retainer tapped right out. The new bearing retainer is on, but about a half inch short of being seated all the way into the tranny case. Does the bearing/retainer need to be pressed on (via the nut) or did the shaft get pulled out too far. Something tells me the shaft has come out too far, so I'm trying to wiggle it forward. No bearings from the front have fallen into the case. Thanks.
Mike

 

Hard to say without seeing it but I usually put a gear on the back and carefully pull it the rest of the way on with the nut to make sure everything is seated. Before doing that though make sure the shaft is all the way in the input. Should be able to look at the synchro assembly to input gear clearance and tell if the output is all the way forward. Nickmil

 

Thanks Nickmil. The shaft appeared to be all the way forward. The gears seemed to line up. So I pressed the retainer on with a gear and the nut. I put the tranny cover back on and tried to shift it through the gears - it's stuck.
Nothing moving in the tranny now, so I don't know what the heck happened, but I obviously have something screwed up. Maybe I pressed the retainer on too far?? The clutch lever is not hooked up since the bracket for it was attached to the transfer case. The tranny should still slide through all the gears. It seems like I'm so close. Problem is, I'm just in over my head. May end up hauling the p.o.s. into a tranny shop an forking out the bucks. Otherwise I own a very large paper weight.
Mike

 

Before taking it in check and make sure the brass blocking rings are not simply stuck on a gear. There should be a little movement in these back and forth. If one is stuck it will in effect lock it into gear. Also make sure the nut has pulled the shaft out into the bearing all the way. If not it will push the shaft in too far and cause the trans to bind up. Nickmil

 

Jeeze, I cant give my old d20 away around here. And it works fine and has the input gear. :?
For the right price though, I'd ship it

 

First off- Nickmil, I want to say thank you very much for taking the time to share your knowledge with me on this. I know time is valuable, so I really appreciate your help.

Turns out the roller bearings did fall out. I have retrieved them all and will try to get things put back together. Seems like this could be a little tricky without pulling the tranny and putting on a bench. I guess I'm only about six bolts away from having the whole thing out anyway. Thanks again.

 

putting the bearings and shaft back in while the trans is still in the jeep is almost impossible,it can be done but it is not worth it,faster eaiser to pull it out and work on the work bench

 

Yep. Everything costs more in southern California. Plus I had a deadline I was trying to meet for a Jeep trip I had planned so I needed to get something right away.

 

Yeah, It didn't take me too long to figure that out. R)
The tranny is now out and on my bench. Gonna take a break from it for a couple a days and take care of some hunnydos.