Joined: Jun 09, 2011 Posts: 776 Location: Bellmore, NY
Posted: Thu Nov 29, 2012 12:57 am Post subject: I'll get my speedometer recalibrated
in a week or so. If that doesn't work, I'm wondering about Speedometer driven gears. If my speedometer is reading high (like 50 when I'm doing 35), so I want to go up in tooth count, or down? I currently have the 15 tooth gear, and I think I go down (like to a 12). _________________ 1952 M38A1
Marine core reinforced rear bumper, military transistorized turn signal upgrade, arctic heater, 11" drum brakes, 200L PTO winch, Huffy overdrive, deep water fording kit, RT 68 vehicle mounted radio, Trac Locs front and rear.
www.danhenk.com
Down would work but what about the last 3 posts? Looks like you have yet to do the easiest troubleshooting step and get the speedo calibrated. And looks like you still have not pulled the rear diff cover and counted the ring and pinion teeth to confirm exactly which gear set you have.
http://www.willysmjeeps.com/v2/modules.php?name=Forums&file=viewtopic&t=7305
Sep 30th When you suspected the speedo drive and/or driven gear were incorrect or you had CJ5 4x gears. You said you had a 15 tooth gear used with the higher CJ rear end but that is the correct gear for your A1. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Jun 09, 2011 Posts: 776 Location: Bellmore, NY
Posted: Thu Nov 29, 2012 2:54 am Post subject:
Wes, maybe I was unclear somehow in the other posts, but I have never thought I had anything but the 5:38 M38A1 axle gears. I think the speedometer would read too low rather than too high if I had civilian gears back there. I asked if I would get more speed if I regeared, and you explained why I wouldn't. I suspected that I had the incorrect Speedometer driven gear and/or drive gear in the rebuilt transfer case that Novak sold me, and you explained how it is the whole ratio of gears, axles, tire size, and transfer case. The axles and tires being correct, and John at Midwest Military selling me the correct 15 tooth speedometer driven gear, I think that only leaves the transfer case or the speedometer. I suspect it's either the drive gear in the transfer case, or the speedometer, at this point. It's a real pain in the ass to pull the transfer case. I have a PTO and overdrive on there. There are several local speedometer re-calibration shops. _________________ 1952 M38A1
Marine core reinforced rear bumper, military transistorized turn signal upgrade, arctic heater, 11" drum brakes, 200L PTO winch, Huffy overdrive, deep water fording kit, RT 68 vehicle mounted radio, Trac Locs front and rear.
www.danhenk.com
Joined: Nov 24, 2010 Posts: 1390 Location: Orem, UT
Posted: Thu Nov 29, 2012 6:21 am Post subject:
Any sort of change to a taller or longer gear (numerically smaller) will result in more speed and a weaker drive ratio. Think of it this way. With 5.38 gears, that means that drive shaft has to spin 5.38 times to one of the axle shafts revs. So you are cramming all this energy to spin the driveline 5.38 times to spin the axle once, torque. Go with a taller gear, say 3.73 and the drive shaft spins 3.73 times to one of the axles spin, less torque. The more the number goes down, the closer it gets to matching the inputs to output. RATIO
Same concept higher up in the drive train in the tranny, low gear is numerically higher or shorter than that of high gear. In our case, 3rd gear in the T90 is a straight shot 1:1 ratio. _________________ Brett
'51 M38
PHOTO DIARY OF MY BUILD
Joined: May 14, 2009 Posts: 972 Location: South Dakota
Posted: Thu Nov 29, 2012 6:56 am Post subject:
You may find it cheaper to just buy another speedometer. Lots on used ones on ebay. I also don't know what the correct speedo # is, but maybe you have another type vehicle speedo put in by a previous owner? Just a thought. John
He has two speedos and both carry the same high error reading. Although he hasn't physically checked them he is convinced for some reason he has 5:38 gears. He has purchased and installed the correct M38A1 driven 15T speedo gear. For some reason he suspects a transfer case issue but there's no reason for that since the transfer speedo drive gear is the same for all three different driven gears. As I posted above the two unknowns are the rear diff ratio and the tranny gear ratios (the tranny is a rebuilt unit from a vendor). It is a remote possibility both speedo's are reading the same amount high and a simple bench check at a speedo shop will confirm that.
At this point, without making the rear diff tooth count and tranny gear tooth counts he is simply hypothesizing and what-iffing. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Jun 09, 2011 Posts: 776 Location: Bellmore, NY
Posted: Thu Nov 29, 2012 1:14 pm Post subject:
I was told, by the people I purchased the jeep from, that the gears in the axles were 5.38. No, I have not checked them personally, although I would assume, if I had lower gears (higher numerically) my speedometer would read lower than it actually does. I can stop by my buddies shop, put it up on a lift, and check them in a few days.
The transmission and transfer case are more of an issue. No, I did not count the gears while they were out for the clutch. Yes, in retrospect, I should have. I have researched this online, and see that there are different gear ratios in different model years of the T90. There is a T-90A1, and a T-90C. I found that there are also several differnt gear ratios in the Dana 18. Novak built the trans and transfer case for me, and they put a keyed 15 tooth speedometer driven gear in the transfer case. The tip broke off, so I replaced it, but I have no idea if that is an indicator that the transfer case has the correct gearing or not.
All of which, brings me to this. I have a keyed speedometer driven gear, and the military waterproof speedometer cable. I don't want to change these, so even if I have a different gear cluster than I should, getting the speedometer re-calibrated might be the way to retain them. _________________ 1952 M38A1
Marine core reinforced rear bumper, military transistorized turn signal upgrade, arctic heater, 11" drum brakes, 200L PTO winch, Huffy overdrive, deep water fording kit, RT 68 vehicle mounted radio, Trac Locs front and rear.
www.danhenk.com
Joined: Jul 18, 2008 Posts: 639 Location: Melrose, MA and Santa Fe, NM
Posted: Fri Nov 30, 2012 7:01 am Post subject:
Hey Deadguy:
Not throwing in more advice but based on what I've been seeing in your posts it sounds like a good idea to put your jeep on your friend's lift rack and check everything out. So far it seems that all the new-rebuilt and restored key components on your jeep were not done as described when you bought it. Checking out for sure yourself sounds like a good start to knowing just what you have.
That's my $0.02 worth.
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x gears. You said you had a 15 tooth 
