Joined: Jun 15, 2014 Posts: 268 Location: Cambridge, Ontario, Canada
Posted: Sun Jan 03, 2016 1:48 pm Post subject: Speedo gear housing question
The T90 in my 52 has some stripped gears in it so I picked up a replacement transmission from a local guy who had it in his Willys pickup.
Since his truck didn't have parking brake installed on the drive shaft like the M38 does, it was missing the lever aassembly for the cable attachment. One of our members here has successfully swapped out this part and figured I would do the same. Upon teardown iI notice 2 differences.
One is the speedo gear itself. My original is a 15 tooth and other is a 21 or 22 tooth. I suspect that 15T is correct but would appreciate confirmation on that.
Second is the housing itself. The M38 has a wide slot for oil to travel and a hole inside casting to lube internal components. The other one has same oval slot but instead of having hole in the casting, it is channeled from the machined face of housing as pictured below.
Either way, both get lubricated the same, just wanted to post the differences.
Just wondering if 15T is correct and what axle ratio would use the larger tooth count?
I'mlooking to put 7.50-16 on my M38 so thought maybe the other speedo gear would be a better choice to keep speedo closer to correct speed
thanks
Brad
Generally the MA, MB and early 2A were 4.88:1. The later 2A and on were 5.38:1 with 4.27:1 and optional gearing. I would stay with the matching drive/driven gear set and housing for your M38. Rather then arbitrarily switch to 7.50-16 tires (a bias ply size) I would select a modern tubeless tire based on actual tire width and outside diameter vs the stock 7.00-16 tire width and OD. This would be Specs:
Load: 1800@45psi
Outside Diameter: 30.50"
Tread Width: 5.80"
Rim Width: 4.5"
Some radials that come close are 245/75R16, 285/65R16.
There are three different length driven gears. one short and two long.
There are two different mount sleeves for the driven gear. One short and one long.
The teeth count stayed the same for 4.88, 4.27 & 5.38 in the CJ's and Military jeeps. Can't help with truck gearing.
The stock m38 is shown below
_________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
The sleeve is the threaded adapter that retains the driven gear and the speedo cable assembly threads onto the end of the sleeve. I can see a threaded short sleeve is already in both of the housings in Brad's photos. You can have Brad unthread one and measure the gear length and the threaded sleeve length and post them here. In the mean time I'll look around and see if I can find long ones to measure. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Jun 15, 2014 Posts: 268 Location: Cambridge, Ontario, Canada
Posted: Mon Jan 04, 2016 11:26 am Post subject:
Thanks for the info Wes. I will stick with original gear then.
As for the tires, the STA tires I'm looking at are 7.50-16 but are radials and not bias ply. They will be going on my rims that i believe are 5" wide (need to peel old rubber off to verify). I will be putting tubes in them as well since the rims are tube type rims so not sure how well they would seat on rim lip.
Brian, I can remove and measure parts if you like. _________________ 1952 M38 project
Brad
Joined: Oct 06, 2014 Posts: 252 Location: South Dakota - Aberdeen
Posted: Thu Sep 29, 2016 12:46 pm Post subject:
I am going to semi-hijack this thread to post my issue. I have been driving my freshly restored stock m38 this summer without a speedometer cable. Just bought one and tried installing last night. I could not get the end to go in the transfer case part. I have looked at quite a few threads, but am a little confused as to what to do at this point. Do I need to pull that gear and take a closer look? I'm thinking where the cable goes into the gear, it is a square sleave and maybe the wrong gear? I rebuilt the transfer case myself, but can't be sure what type of cable was used before or if it was original to the jeep.
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