Hemi into a 1972 J4700

[Modfan]

I'm kicking around putting a 5.7l hemi and 645rfe trans into a 1972 j4700. I can't find anyone who has details on a HEMI swap, has anyone did this swap? I think, I have everything figured out except adapting the 645RFE to the Dana 20 transfer case.

Does anyone make an adapter to connect the 645RFE to a jeep Dana 20?

[rocklaurence]

Dont worry about the D20 case. Youll save time and money by installing a Dodge Tcase that is already bolted to the transmission that you purchase for the swap. Get everything from the same Dodge 4x4 donor

[will e]

Make sure to grab wiring harness and looms too! It sounds like an interesting swap.

There is a guy here in AZ that has a Dodge in his wagoneer but I don't think he's a board member. I will see if I have a picture of it.

[Mopar_guy]

Have you seen this thread? https://www.fsjnetwork.com/forum/viewto ... 12&t=20501

[Modfan]

There is no donor, I have a complete 5.7l and 645RFE 4x4 trans. I have no problem with the harness, motor mounts, or the rest. I just need to adapt to a Dana 20 transfer case.

[Modfan]

Have you seen this thread? https://www.fsjnetwork.com/forum/viewto ... 12&t=20501

Thanks for the link. Lot of good details.

[Stuka]

Dont worry about the D20 case. Youll save time and money by installing a Dodge Tcase that is already bolted to the transmission that you purchase for the swap. Get everything from the same Dodge 4x4 donor

The factory NV t-case will be driver drop, it won't work unless he swaps out the front axle.

There is no donor, I have a complete 5.7l and 645RFE 4x4 trans. I have no problem with the harness, motor mounts, or the rest. I just need to adapt to a Dana 20 transfer case.

I would call advanced adapters or novak and tell them what you are doing. The trans that you have uses a pretty standard t-case mounting setup, round NP pattern, though I am not sure on the spline count. Could be 23 like Jeeps, or 28/31 like some other trucks.

The big issue, and this may be the deal breaker, is the transmission pan. The D20 is not a very wide t-case case, and people have issues with the drive shaft hitting the trans pan of other transmissions. If thats the case, you may need to look into using an 80's dodge NP208 as its passenger side drop. The vast majority of NP/NV cases are driver drop.

[akguy09]

To be honest, I wouldn't spend alot of money and effort trying to adapt a D20 if other options exist, even though its a gear driven T-case, its good not great like a 205. There are chain driven cases that are better

[Stuka]

To be honest, I wouldn't spend alot of money and effort trying to adapt a D20 if other options exist, even though its a gear driven T-case, its good not great like a 205. There are chain driven cases that are better

Thats a good point. A 5.7L Hemi puts out more torque than any vehicle that came with a D20. And the D20 is already known for having rear outputs break.

[Herk]

A Dana 300 would be a better choice transfer wise, the adapter to a Dana 18/20 is about $700. But if I were doing the swap I would use a later model transfer out of a RAM 1500 or Grand Cherokee similar to the year of your engine and transmission combo. If I were making the swap, switching to drivers side drop wouldn't worry me much as I would also plan on replacing the axles. The original axles/brakes on these vehicles are oddballs, not particularly strong and some parts are getting impossible to find (12" brake drums).

[akguy09]

Just curious what application this Hemi and Trans is from? Is it a Ram pick up?

[tgreese]

Mmm. Is a D300 any wider than a D20? Seems unlikely. They are both gear driven transfer cases that were used in the CJs. The rails of a CJ are narrow compared to the J-truck. Pan interference seems likely.

I wonder if the proper course is replace the closed knuckle front axle of a '72 with something that's driver's drop. Then no worries using the transfer case from a Dodge (aka Ram). A D60 front from a Dodge truck? Or D44HD from a later J-truck, converted to 5-lug with Ford parts if the OP wants to keep 5-lugs? A J4700 will have the 5-lug 60-2 rear axle, which has its own issues.

[Modfan]

Sounds like my best move is to go ahead and drop a 304 in it and roll.

[Stuka]

Sounds like my best move is to go ahead and drop a 304 in it and roll.

That would certainly be the quicker way.

But it would not have all the advantages of a modern drive train. It just needs to be clear up front that adapting a 50 year old vehicles to use a new drivetrain won't be plug-n-play.