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Need Info on M38a1 Transfer Case
Posted: Sat Sep 02, 2017 6:59 pm
by Restomod
Just bought a 1955 M38a1 and found that water had been sitting in transfer case and EVERYTHING is totally rusted and seized up.
I need a new transfer case housing.
I found a "NOS" one on the internet, but it as noted as follows
"Willys-M38-M38A1-CJ3A-CJ5-NOS-Transfer-Case-Housing-G-740-G-758"
I have two questions-
1. Is this the correct transfer case for a 1955 M38a1?
2. Is the M38a1 Transfer Case housing really the same for all these Jeeps?
Thanks in advance.
Hello restomod, I am moving your post to the technical board. This board is for evaluating the quality of dealer parts and dealer service.
Posted: Sat Sep 02, 2017 8:16 pm
by wesk
First please confirm that although you found the entire transfer case rusted and seized you are only looking for a transfer case housing? Then confirm which housing, front, rear or center main?
Q is Main center, K is rear housing
Front
Rear
There are many transfer cases that will fit if you use the entire case with it's matching internal parts.
What makes up the one and only M38A1 transfer case is the military style shift lever sahft, the vent on the front case and the correct speedo gear and nipple.
I'd suggest re-evaluating your current case for restorability. usually a simple bead blasting will return a really rusted case to service. Then replace gear and bearings damaged by the rust.
Posted: Sat Sep 02, 2017 9:59 pm
by Restomod
Thanks for moving this to correct place.
I wish bead blasting would do it.
In your diagram this would be the "Q Case".
All gears and shafts are ruined.
I soaked the whole thing for weeks in various penetrating oils.
Tried pushing out the shaft out using a 40 ton press with intermittent beatings with drift and mini sledge.
Even used a blunt chisel and mini sledge to try to get any of the gears to rotate.
Nothing will budge.
Since I can't get internals out, I will need to start over with a new case.
Just want to make sure this is the correct one.
Posted: Sat Sep 02, 2017 10:46 pm
by wesk
Do you intend to buy every gear, bearing, shafts, shift levers, pins, keys, etc & so on? That can get very expensive fast.
I would suggest buying a complete used Transfer case, preferably the large main shaft version and if it came from a civvy jeep then most parts I mentioned were peculiar to the M38A1 transfer case you should be able to use off your old case.
The key difference on the various D-18's is the intermediate shaft diameter.
Here's a good link for serious info and procedures:
http://www.novak-adapt.com/knowledge/tr ... s/model-18
Versions
Early Military, 1941-1945
Military versions of the 18 built for the MB & GPW wartime Jeeps have a 1.97:1 ratio low range and a 1:1 high range. These early versions featured a 3/4" diameter intermediate idler shaft and dual shifters. These transfer cases were only married to the Borg Warner T84 three speed transmission and had a 3-5/32" input locating bore.
Early Civilian, 1945-1946
A handful of the earliest civilian Dana 18's that were married to the side-shift version of the T90 feature 2.43:1 low range and have a 3/4" intermediate shaft. Relatively few examples of these exist but the reader should be aware of it. They were developed for the prototype 6x6 Tugs (only 16 of these were made). This transfer case came in the preproduction 1944 CJ-1 and 1944-1945 CJ-2 and were installed in the CJ2A up through serial number CJ2A-24196
.
Mid Civilian, 1946-1955
With military restrictions freed up and Willys eyeing the civilian, utility and agricultural markets, the Dana 18 was improved with a lower 2.46:1 low range gear ratio. The intermediate idler shaft was increased to 1-1/8", using caged needle roller bearings. The rear PTO port began to see serious use as a driver of accessories ranging from pumps, winches, generators, farm implements, etc. The locator bore continued to be the 3-5/32" diameter. Casting numbers of C18-15-10 have been seen on these versions.
Later Civilian, 1955-1971
In 1955 (this varies by a year or so on some models; no doubt while Willys-Overland was using up its remaining inventory) Jeeps received the Dana 18 with an 1-1/4" intermediate shaft. This improvement was not intended to increase the shear strength of the pin, but to increase the bearing area and the number of bearings. Free needle rollers, then, replaced the earlier and significantly fewer caged needle rollers. The locator bore continued to be the 3-5/32" diameter.
Final Civilian, 1966-1971
The "large case" version of the Dana 18 was the most improved version of all. It was only found behind the Buick V6 engine with its T86 and T14 transmissions. The case casting used was that from the Dana 18's progenitor, the Dana Spicer Model 20. This case featured a 4" locating bore and a single stick shifter and new front output cap. The front output assembly did not provision for a shifter mounting point, as the shifter was anchored to a transmission bracket. The internals were essentially identical with the standard Dana 18. This version is best thought of as Dana 18 guts in a Dana 20 shell. Individuals can build a "Super 18" by copying this version.
Posted: Sun Sep 03, 2017 7:52 am
by Xamon
As a note from someone who tore down a rusty one of these, the shaft that must be driven out, KK in the first diagram which is in the center hole of Q, only drives out one way as it is all tapered. I do not remember which way it comes out but someone will. Also that shaft is a $%#$^ to get moving even when you are pushing it the right way, took me a fair time with a 2 pound hammer to get it moving.
Posted: Sun Sep 03, 2017 8:33 am
by wesk
It comes out towards the rear. That is why it has a plate bolted there to keep it in. Make sure you have a sturdy set of Brass Brass Brass punches and drifts.
There are a few great guides that will walk you through the rebuild of your D-18:
From Rick Stivers on Willys Tech:
http://www.willystech.com/wt/Model18TCa ... rCase.html
Novak's Guide:
http://www.novak-adapt.com/knowledge/tr ... uild-guide
Advanced Adapters:
http://www.advanceadapters.com/tech-vau ... dana-1820/
FourWheeler:
http://www.fourwheeler.com/how-to/trans ... spicer-18/
Posted: Sun Sep 03, 2017 9:42 am
by 4x4M38
Rick Stivers' is the one I'd grab first.
Yep, that one shaft only goes in and comes out one way.
Posted: Sun Sep 03, 2017 10:01 am
by wesk
That's why it's first in my list!
Posted: Sun Sep 03, 2017 10:27 am
by Restomod
OK, I will try one more time to get the shaft out, but I have already done everything suggested.
But in case it doesn't come out, I need alternatives.
No one has still commented on whether the case noted in the original post would work.
I must emphasize that nothing inside can be salvaged - EVERYTHING is going
to have to be replaced.
If I go with a used one, will ANY late Dana 18 or 20 bolt up the M38a1 tranny?
How will I know a used transfer is any good?
Don't want a junker that I would still have to buy parts to rebuild?
Any leads on where to find a good used one would be appreciated.
Posted: Sun Sep 03, 2017 11:40 am
by 4x4M38
Buying a used one....
Unless you buy one from someone you know
and trust, or from a reputable dealer...
The only way to really evaluate is look at it yourself.
Several things are fairly easy to determine wear,
but there are some things that will require disassembly
and checking wear, finish and tolerances.
Rick Stivers' guide has a pretty good treatise on all that,
but does assume you have the transfer on your bench
and are pulling it apart.
Where are you located? Someone may have one near you.
Posted: Sun Sep 03, 2017 12:54 pm
by radtech
If you are talking about the NOS cases from armytankguy,that is Brent Mullins at Mullins Jeep parts.I think they came out of a German Army warehouse with a lot of other M38 and M38A1 parts.He said these have the 1 1/8" counter shaft.
Posted: Sun Sep 03, 2017 6:37 pm
by Restomod
I'm in the DFW, TX area.
Posted: Sun Sep 03, 2017 7:02 pm
by Restomod
Yes the add for the bare case is from armytankguy.
Will any Dana 18 or 20 Transfer Case work with the M38a1 tranny?
Posted: Sun Sep 03, 2017 9:47 pm
by wesk
No one has still commented on whether the case noted in the original post would work.
Restomod, I clearly posted the differences above on cases. If you are not going to show the case to us we can't make that call for you.
OK, I will try one more time to get the shaft out, but I have already done everything suggested.
But in case it doesn't come out, I need alternatives.
Have you tried heat & cold? Are you using a hydraulic press? As a final resort before you start tossing money at it try an auto machine shop.
Posted: Thu Sep 07, 2017 9:56 pm
by Restomod
OK finally got the shaft out.
Got a really useful trick for anyone that has really rusted up transfer case internals.
I mean gears that are so rusted and fused that a chisel and sledge would not rotate them.
OK here it is-
Go to s Harbor Freight and get their cheapest pneumatic chisel that comes with attachments.
Take the punch attachment and grind the tip flat so it has about a 1/4" flat on the end.
Crank up the air pressure up to 90#and lean on it hard and pull the trigger.
In about a minute, switch to the opposite (wrong) side and hammer for 5 seconds.
The repeat.
After 2-3 rotations, it started to move and finally worked loose.
Unfortunately, I don't think there is anything that can be salvaged.
Thanks for the help & info.