Posted: Fri Sep 18, 2015 11:26 am Post subject: Axle and engine compatibility
I apologize if this was asked previously, I've been searching through past posts but haven't been able to find the answer. I just picked up a semi-complete 52 M38. I'm essentially missing the important pieces which make it "go". Axles, transmission, transfer case, and engine. I found plenty of information regarding the specifics of the T-90 and Dana 18.
My first question is regarding the axles. I know the M38 used a Dana 25 and Dana 44, but that is where my knowledge stops. Will any of the axle assemblies from the same period work, or are there major differences? I want to build this Jeep correctly, but realize that parts are getting hard to come by.
The other question is regarding the engine. From what I've been reading, there are some slight variations on the L-134. I currently have a spare L-134 sitting around from a CJ-2A that is in great condition. Could I use this for the M38 or should I sell it and keep looking?
Joined: May 30, 2014 Posts: 3447 Location: Texas Hill Country
Posted: Fri Sep 18, 2015 4:09 pm Post subject:
Hello Ewan,
Welcome.
I may not be able to answer your questions but have a suggestion.
It will help you as well as the assemblage here in answering
questions if you and we know what level of restoration you
are planning.
A factory restoration is very specific and exacting as to what
is appropriate on an M38.
A motor pool restoration is much more lenient, but still requires
military equipment, just what was appropriate and available
at the moment in time your M38 is trapped in.
Both versions will enable you to enter and show your M38
in military vehicle contests.
The third level is daily driver. This one is basically anything that
allows you to safely and reliably drive your jeep, but no
restrictions as to what you want to install.
I will say that any L-head motor will fit in the M38, and
depending on whether your spare motor has the military
specifications like the water pump bypass tapped port in the
front of the head, could be okay for a motor pool class restoration.
The difference in factory versus motor pool is your jeep when
restored would have to have the same style motor and
appliances that came from the factory.
Other parts would follow the same pattern as far as applicability.
Axles: As a general rule any 25 or 44 axle built by Dana / Spicer for a universal jeep from 1948 thru 1971 will bolt in. There will be subtle differences in the 25 steering knuckles and drive axles. There will be different axle final drive ratios. And in a few cases differences in brakes.
The L134 engines built by Willys & Kaiser from 1948 thru 1968 will all fit. Keep in mind that only 2 casting numbers were factory correct for the M38 641087 and 804380. What makes an engine chassis specific is the serial number, not the casting number. IE a 641087 casting with a 2A457869 serial was installed at Willys in a CJ2A. If it had a serial 3A62785 it was installed at Willys in a CJ3A. If it had a serial V346271 it was installed at the Willys factory in a CJV35U. Finally if it has a serial MC357893 it was installed at Willys in a M38. Without that serial there is absolutely no way to prove beyond a reasonable doubt what chassis that engine came in.
Same goes with cylinder heads. There were many different cylinder head casting numbers used from 1941 thru 1971 on the L134's. The 800376 heads that came on ALL M38's also came without the water pump bypass port for the CJ's and power plants setups of that same period.
Based on your opening post you are building a driver M38 and seem to be willing to use what you can locate without any qualms. If you do wish to venture into the motor pool class for judging then with few exceptions you will need to stay with M38 specific factory installed parts. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Thanks again. It sounds like I'll be somewhere between motor pool and driver. It sounds like using my existing engine is an option, but I'll keep an eye out for the correct block. The casting is 641087 with no serial number, I can't find one anywhere. Nothing stamped on any of the pads and nothing above the water pump. The head is 640161 so this has to be from a CJ-2A like the previous owner said. Anyways, I want to be as close to original as possible, but I don't mind if serial numbers don't match. The end goal is to have a nice jeep I enjoy driving on a regular basis, and eventually pass it down to my children. My boys are already fighting over the CJ-5
That head work but you will have to Plud the bypass port in the pump. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
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