Stock trans or a jeep trans?

[amchornet]

So I plan on starting my head swap soon. My question is should I use the stock trans or swap in the one from the jeep. I really did not want to mess with diffs just yet so what rpms would I pull with the jeep trans and eagle diffs on the highway? I have to check but since I have an 85 eagle sedan I think I have the 2.35s. I was wondering if it would work ok thats all?

[Billman]

Putting a 4.0 head on will make your engine breath better, this will give you an improvement in performance and efficiency but really will not have an effect on rpms. Putting in an overdrive transmission will mean changing your driveshafts crossmember and possibly the flywheel if you want to go fuel injected. Both projects can be done individually. Depending on your transmission gears you will have different rpms as you go through the gears but with a 4 speed your final drive gear will be a little lower rpm at the same speeds than a 904 would

[BenM]

Any overdrive would be useless with the 2.35 axles.

There could be a small changes. You could swap in a lockup auto for a non-lockup. That would lower highway engine speeds a little. The earlier 9xx transmissions had a higher first and second gear, but that would make your first and second slower and wouldn't do well with the 2.35 axles.

Most Eagle transmissions will hold up just fine to the upgrade, so I wouldn't worry.

I'd consider the swap if you're bringing the fuel injection over. You can avoid 4th on the AW4 or 5th on the manuals until you change the axle gearing.

What Jeep transmission do you have?

[amchornet]

Oh yes sorry its the aw4 trans and I was thinking of using it an just using the tow mode. I found a engine rpm calculator site for jeep diffs and I belive if I did it right I would be turning 72 mph at 2000 rms in third gear. That does not sound to bad to me...I am planning on using the whole fuel injection system with the 4.0 head. The stock trans cross member wont work with the aw4??... I suppose if it is longer...I knew about the drive shafts tho.

[eaglefreek]

I've installed an AW4 and have 3.07 gears. It really needs 3.55's and I plan to install those one day. With the 3.07's, you have to be going 75+ mph for it to stay in OD. Now if you turn the OD off and use it as a 3 speed, I think it is still worth the effort. The AW4 seems to be more efficient and the shifts points  are better also. Just remember, it's not a direct swap. There are a lot of modifications that need to be done to run the AW4.

[BenM]

The AW4 in 3rd will drive just like a 3 speed with lockup, provided you bring the transmission controller over with it. I feel that it's overall a better transmission to live with.

[amchornet]

Ok my bad while working on pulling the engine and trans I discovered it is a 42re trans. It looks smaller than the aw which makes me think it would fit better...any suggestions?

[BenM]

A 32re is 998/999 with an overdrive unit bolted in place of the tail shaft extension. I think a 42re is an A500 done up the same way and the A500 is based on the 904 as well. The OD unit won't bolt to an older transmission body because there are internal passage differences to route fluid to the overdrive unit.

I don't know about 42RH valve body swaps;  you may either need to bring the whole computer over or use a Megashift.