View Full Version : Axle compatibility

07-15-2019, 07:50 PM
I bought a 1958 CJ5 frame. I'll be working from there one part at a time. When buying axles, I'm assuming they have to be compatible as far as ratios, etc.? Also can someone give me an answer on whether or not the axles are above the springs or below? Thanks

07-15-2019, 08:43 PM
In stock form, the axles are above the springs. To create a cheap lift, you can run the axle under the springs, but you have to cut off the spring perches, and weld them on the top of the axle. That is just a nutshell.

As far as ratios, you have a few options. It all depends on how and what you want to do with your rig. Highway speeds require a higher ratio gearing, i.e. 3.73:1, but a stock 4 cylinder would be doggy at lower RPMs. A stock 4.88:1 will limit you to 50 mph max, and a 5.36:1 is good for only 47 mph max.

07-16-2019, 07:33 AM
Don't forget your tire size. If you increase the height of the tire, it can have a significant impact on final drive ratio. A 2" diameter change from 26 to 28 for instance, will knock a final drive effective ratio down numerically .25 points. In other words the 4.88 acts more like a 4.56.

The front ratio needs to be the same as the rear ratio unless, you are sand dragging. If they are not you will break something eventually or, right away. For this reason the tires must also be the same size.

In an attempt to knock some of the ratio out of my 5.38 CJ3A, I increased the tire size to the biggest stock looking NDT's KW had to offer that would not hit at full turn. I was able to significantly increase the tire height and reduce the effective ratio by a lot. I can now go 51 at recline! Haha, truly gotta love cruisen' slow... real slow.

07-16-2019, 10:53 AM
Thanks so far for the input. Glad I was able to stumble upon this great resource! On another note: I was able to find the serial number on the frame. Looks like it's a '61; not a '58.

07-16-2019, 11:38 AM
Looks like it's a '61; not a '58.

You have now been introduced to the First Rule of Jeep:

1. What you see is what you have. Trust only what you see with your own eyes.

And, the Second Rule:

2. Never say "Willys never ..... ." We have found exceptions to just about everything.

Welcome to the group - post some pictures.

07-16-2019, 05:00 PM
Are all Dana axles the same width; or are they specific for year and model?

07-16-2019, 09:00 PM
There are many width Dana axles in various set ups. Basically by same model number, the center section will be the same. The differences in the same models lie in the axle tube and shaft length, brakes and spring mounts etc. Things that make it unique to the vehicle. You could say that normally similar model year vehicles would have the same width (track) axle. It is also possible that the same axle track was used in different models and, different O.E's.

A bit of trivia... the model 41 Axle used in early Willys is the same axle that was used in the 41 Mercury. Back then the model 44 was an upgrade from the model 41. They are very similar in size and capacity. The 44 however became a popular choice for light trucks of the day. A thicker ring gear and larger carrier offset allowed for many different ratio combinations. The 41 had one ratio, 5.38. Sticking with a model 44 for your build is a wise choice. Parts and ratio's are readily available. It is a very strong axle. I used one with stock gears and axle shafts, in an 800HP wheel standing S10 Chevrolet. It was one of the last ones made for the Jeep Comanche pickup. Its Track was to wide for the S10. It required large back offset rims.

07-16-2019, 11:47 PM
The info I've found on my jeep says D27 for the front and D44 rear. Would you specify frame/leaf spring width to order?

07-17-2019, 06:32 AM
Are you speaking of purchasing a new axle from someone? In that case, yes. You would specify several things.
On an early Jeep:

1) The axle spring perch type and location (Leaf Spring top or bottom of axle) Jeeps are bottom stock.

2) The overall axle width.

3) The axle flange requirement.

4) The ratio.

5) The differential type.

6) The pinion flange/yoke requirement.

These are the main things. There is more.

I think you can go here and get a good idea. https://spicerparts.com/applications/crateaxle

If you can find a used model 27 front and a 44 rear out of a CJ you would be ahead of the game. Rebuilding those would save a lot of money.