Gear ratios

skratch

Well Oiled
Jun 15, 2017
1,113
bernardo nm
First Name
john
Willys Model
  1. CJ
Willys Year:
  1. 1958
Is there a way to determine the front and rear gear ratio w/o the tags ? I can't find any markings on the housings.
 
Rotate one axle and count the revolutions of the pinion yoke. 5.38 gears would be 5 1/3 pinion rotations, etc. Or, take off diff cover and divide pinion teeth into ring gear teeth.

Not quite Joe but nice try. The spider gears will eat up 50% of the revolutions, so 5.38 will turn about 2 5/8 times, so you double that number to get the ratio.
John's CJ5 is a 1958 so in all likelyhood they are 5.38. Optional could be 4.27. Those are the only 2 choices. Hopefully his front and rear are the same ratio.
diggerG
 
Thanks Greg & Joseph, reason I ask is the PO put over sized tires on it ,,,, Goodrich 30x9.50 R15 LT. In this sandy soil it seems to bog down way too much. Engine is up to snuff. I run low pressure,, 18-20 lbs. From what I've learned both front & rear ratios are same. Would a smaller tire dia. help ? I don't need mph, just more torque to the ground. Any suggestions appreciated.


Thanks ,,, John
 
They aren't that much oversized. It's 30" tall. You are only playing with 72 hp there. I'm not familiar with your N. M. soil but it must be pretty loose. Just stay in 1st gear low range. What tread are your tires? mud and snow type treads don't work too well in sand. Where I am we have Cape Cod sand, and believe me it is as loose as sand can get.
diggerG
 
They aren't that much oversized. It's 30" tall. You are only playing with 72 hp there. I'm not familiar with your N. M. soil but it must be pretty loose. Just stay in 1st gear low range. What tread are your tires? mud and snow type treads don't work too well in sand. Where I am we have Cape Cod sand, and believe me it is as loose as sand can get.
diggerG

They are mud/snow tread. The soil here varies by area, mostly sandy mixed w/ clay in lower areas, not too bad but then you might hit an area that's like dry quick sand, if you get into that it's likely axle deep time. I think you're right about the HP. Someone told me I needed a winch, problem is the only thing to hitch to is maybe a jackrabbit.

Thanks , John
 
This brings up a question I have and I hope you don't mind me asking it here. I have a wagon as a parts vehicle and using the axles out of it for my truck. And the ratios are different than the truck axles. I want to use the axles that give me higher
Road speeds with lower engine rpm. Did the wagons have higher road speeds than trucks? Or the other way? Also with a 5.38 mean five revolutions of the drive shaft mean the axle or tire turns .38 of a revolution? BCD.
 
This brings up a question I have and I hope you don't mind me asking it here. I have a wagon as a parts vehicle and using the axles out of it for my truck. And the ratios are different than the truck axles. I want to use the axles that give me higher
Road speeds with lower engine rpm. Did the wagons have higher road speeds than trucks? Or the other way? Also with a 5.38 mean five revolutions of the drive shaft mean the axle or tire turns .38 of a revolution? BCD.

Station wagon axles are not compatible to a truck. The rear axle is way too narrow. And the wagon will have different ratios than the truck. But the front axle will bolt right in.
diggerG
 
Really? I didn't notice. I got the front wagon axle in my truck now. The back is the original truck one. I know the ratio is different because when I put it 4x4 it does some "skidding". Guess llI rebuilt the old front axle and put it back in. I'm going to measure the wide of the 2 back axles and see for myself.

I'll let you know my findings. BCD.
 
Also diggerG.

Does the axles ratios on a wagon give higher road speeds at the same engine rpms? Compared to a truck?
BCD.
 
Regarding sand, I would drive my MB onto sand bars in the Mississippi river. After sinking in 6-8 inches into the sand the little Go Devil just would not Go. I would have to back out the track in. This is with stock 4.88 diffs (is that right, I always forget the MB gear ratio but its higher than most later jeeps) and 6.00x16 NDTs. There was a balance between low and high tire pressure. Low pressur helped keep the tires from sinking in but seemed to strain the engine more. High TP would sink in faster but I could keep up my speed and sometimes get thru a soft spot.
Get a farm Jack and some traction mats, they can get you out of most situations. Or, I have used a pointed dig in type boat anchor to get just enough grab to pull out with a winch.
 
I haven't driven on Cape Cod sand, but I've driven thousands of miles in the last 40 years from Wauwinet to Great Point and Coatue (NANTUCKET).
Your 2 issues are tread pattern and tire pressure. I run 8-12 PSI depending on which Jeep I'm driving (46 2A or 53 3B).
Both run 31x10.50 R15's, but a closed tread pattern with ribby style works better. I'm sure I'll get some disagreement, but my 8" wide wheels are better than my 9" wide.

There was a guy our there with a CJ7 with 33" BFG's that sank like a rock within 100 feet of the gatehouse. After the third time pulling him out in the first mile he turned around and went home. Mud tires are bad in sand...

Your problem is not gearing.
 
Regarding sand, I would drive my MB onto sand bars in the Mississippi river. After sinking in 6-8 inches into the sand the little Go Devil just would not Go. I would have to back out the track in. This is with stock 4.88 diffs (is that right, I always forget the MB gear ratio but its higher than most later jeeps) and 6.00x16 NDTs. There was a balance between low and high tire pressure. Low pressur helped keep the tires from sinking in but seemed to strain the engine more. High TP would sink in faster but I could keep up my speed and sometimes get thru a soft spot.
Get a farm Jack and some traction mats, they can get you out of most situations. Or, I have used a pointed dig in type boat anchor to get just enough grab to pull out with a winch.

You figured it out John. I still have my set of 11L x 15 farm implemment (airplane tires) tires that I used in the 70's. a little 4 cyl Jeep would float over the loosest sand you could find at 7 or 8 psi. They were not traction tires at all though. And yes as well on the MB ratios. They were great for their intended use but the gears were not low enough for peacetime uses. Drive an MB and then a CJ2A and you will feel the difference. The Warner T 90 and civvie Spicer BrownLipe was a much better ratio combo also. And any 6.00 x 16 is a poor choice for tires anywhere except maybe plowing snow with M&S's.
diggerG
 
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I haven't driven on Cape Cod sand, but I've driven thousands of miles in the last 40 years from Wauwinet to Great Point and Coatue (NANTUCKET).
Your 2 issues are tread pattern and tire pressure. I run 8-12 PSI depending on which Jeep I'm driving (46 2A or 53 3B).
Both run 31x10.50 R15's, but a closed tread pattern with ribby style works better. I'm sure I'll get some disagreement, but my 8" wide wheels are better than my 9" wide.

There was a guy our there with a CJ7 with 33" BFG's that sank like a rock within 100 feet of the gatehouse. After the third time pulling him out in the first mile he turned around and went home. Mud tires are bad in sand...

Your problem is not gearing.

Keith
I have never done Nantucket but it has to be like the Cape. And I probably did no more than 200 miles on Cape Cod sand..Nothing like your experience that's for sure. Same geology for both I'm sure (glacial melt). I recently found (on a Jeep wagon) 2 machine shop modified 15 X 8" Ford pickup or Mercury wheels that were cut and widened by welding a spacer between the 2 pieces. 1 center was widened out, the other was on the rear and not widened out. They were the old MBBA standard for wide 8.20 x 15 street tread tires for beach running. and that worked good. You are right on about tire treads and pressure. That guy with the CJ7 thought horsepower and traction would get him somewhere. Another physics lesson learned the hard way. LOL!!
diggerG
 
6 cyl wagons are usually 4.27 and 6 cyl trucks usually 4.88. That's about a 13% difference.
diggerG
6 cyl wagons are usually 4.27 and 6 cyl trucks usually 4.88. That's about a 13% difference.
diggerG
[.

So if I understand this right, 1 turn of the drive shaft turns the "ring gear" 4.88 revolutions, therefore a truck would have a higher road speed than a wagon at the same engine rpms?

BCD. Sorry for the dumb questions just trying to under stand the ratios and their outcome rpm. ]
 
The opposite. 4.88 driveshaft revolutions equal 1 ring gear rotation. 4.88 has LESS road speed than 4.27.
 
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