Posted: Mon May 09, 2016 7:57 pm Post subject: Lower gear ratio for axles
I have been thinking about lowering the gear ratio on the ring and pinion for my 1952 m38a1. I'm not sure what size to go with yet, or if its like the m37 and only has one option. I'm a little on the fence about it now though since having problems with my m37 rear ring and pinion. I put a 4.89 in it changing out the old 5.83, but when I try to get the preload on the pinion, and I tighten the companion nut on the end of the pinion to 300 ft lbs, it siezes up completely. I'm suppose to have up to 75lbs foot turn on the yoke, but it won't move at all. I bought an extra shim pack from vintage power wagon, but I have tried all the shims in, and all the shims out just to see if I could get it to move.
Can anyone tell me what it is I'm doing wrong here...please...I can't even get to the rest of the procedures of the backlash, pinion depth, and placement until I get the preload down on the pinion. Does any one know how many shims, or should I say measurement of the shims for the 4.89 ring and pinion replacement? Its a 1953 dodge m37. Also what are the ring and pinion options for low ratios on the 1952 m38a1? And is there the same problems on the m38a1 that I'm having on the m37? Thanks for any help at all guys. I could really use some experienced knowledge on this bear.
It seems you are using the term "lowering" gear rations where you actually mean raising them. In the auto world higher gears have a numerically lower ratio number.
So with the M38A1 which came with a very low 5:38 to 1 ratio (numerically high) You could go to higher 4:27 to 1 ratio (numerically lower) to raise your highway speed and keeping engine RPM's lower.
The pinion shaft preload is not determined by the tooth count of the pinion. It is determined by the clearance of the bearings. The only way to find the sweet spot is to keep adding shims until you get the desired preload. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Thanks to the correction, I can see why that is. Raising the number just lowers the speed. Well if you want to keep your rpms down to normal of course. The ring and pinion tooth count I mentioned was just to put the Intel out there of what I was doing. I know it has nothing to do with pinion preload. The problem I'm having is I have put all the shims in made for this truck along with an extra pack of thinner ones, and still lock the yoke up tight where it can't even move.I was just wondering if anyone knew of a ballpark number .098,.110, .120, ext. Its just an answer no one seems to know, and I thought I would throw it out there, to see if maybe there was something I didn't catch during installation . Thanks for the responds though. Unfortunately I guess I'm going to have to spend the 1500 per axle, to have someone do it. Just sucks because I already have 1300 in the one axle already. There's no way I'm going to do this for the jeep if I'm having this much trouble with the m37.
The M37 Chrysler corporate axles are a wee bit different animal then the much easier to work on Spicer/Dana units in the jeep. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: May 14, 2009 Posts: 972 Location: South Dakota
Posted: Wed May 11, 2016 5:37 am Post subject:
Just buy a Saturn Overdrive for the A1. Much easier. Did you try re-using the old shims and amounts and original configuration on the new pinion in the M37? When you read the manual, they say to measure the old pinion depth before dissassembly. Then start with the new pinion there. I've never wanted to mess with my M37's. They don't have the power to pull it much faster anyway. John
Good point John. Unless you are upgrading the 230 flathead 6 to something snorty and the transfer case to one with more fluid capacity and less heat generation the higher gear ratios will result in a lot more maintenance at the engine/tranny/transfer. I've gotten used to the 50 MPH downhill ability of my stock 54 M37 over the years. I took a cruise in a M37 down in Milwuakee a few years ago that was upgraded with Dana 60/70's, modern NP tranny and transfer and Dodge small block V-8 and it was like being another world! _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
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John
