4.10 Or 5.38?

Currently running a 5.38 Dana 25 with the F134. Found a nice Dana 30 in 4.10 today and was considering making the D30 5.38 to match the rear. The guy I bought the axle from thought I was crazy for not considering changing the rear D44 to 4.10 (to match the new front) instead of going 5.38 on the D30.

Questions:

1. Not planning on a lot of highway driving, but will I be able to get 55mph with an overdrive and the 5.38?

2. Will I need to get a new carrier if I change the 4.10 to 5.30?

Opinions please!

 

Same carrier and same differential.
4.10 is about as high geared as you can use with meager F-134 HP.
Any higher ratio is too much for a Willys engine.
5.38 gears and 25% O.D. is the absolute best gearing you can use with the little Willys engines.
5.375 x .75 = 4.03 final drive ratio
So 4.09 differentials is O.K. if you cannot afford an O.D.

 

I regeared my D30 to 5.38. I drove it in fwd around the yard and it was a turd.

 

A little technical for my understanding. Please elaborate on 'turd'. How was it geared prior? Mine's currently 5.38 and don't mind the low end, especially in the woods. I'm only on the highway for a few miles at a time, so top end is currently not a big deal.

 

Good info, thanks man! I think rebuilding the axle will be this summer's project, with an OD if I get that far.

 

Yeah I tried running 4.88 differentials with 25% O.D..
I noticed an immediate drop in available torque.
And that was a very strong running F-134.
Went right back to 5.38 gears with O.D.

 

A fair amount of the equation is also tire size (diameter). The F134 Jeeps through in the 1960's came with a 4:27 axle ratio as standard, not too far off from the 4:10's your considering. These Jeeps were spec'ed with around a 28" tire and were able to easily run 60+ mph on the road, but in low range, would crawl pretty well too. They were a very good compromise, in my opinion, and I always liked the ratio when used with a smaller, by today's standards, tire diameter.
The only way I could ever run close to 60+mph with 5:38 gears was with an overdrive.
It all depends on what your use is, road or trail, and what tire diameters you intend to run. I personally would favor the 4:10 ratio for all-around use if you don't already have an overdrive.
-Donny

 

Lemme clarify my statement. When I swapped in my D30, I drove the Jeep in FWD mode to figure out whether I wanted to keep the D30 gearing or D44. It was a turd with the D30 gearing, so I swapped in the 5.38s that matched the rear.

I run 31" BFG ATs.

 

Got ya...wasn't getting the FWD part.

 

Interesting I will be running a 30% OD with 5.38's and a T-90A I plan on using the OD only as a fourth gear. In all the off road stuff I did in high school with my Jeep I never thought I needed to split a gear (if I had I would have gone with the 25% OD) I plan on running 235/75R-15 tires about 29" tall for both my hwy tires and my off road tires. Well warmed up 134L

 

That's all I'd need and OD for also. Although it would be interesting to see how it performs on the road (hwy) engaged all the time.

 

Where are you getting a 30% overdrive, I've never seen anything but a 25% overdrive.

 

Herm:

Overdrive Types | Herm The Overdrive Guy

 

I am in the same position.. I have a 5.38 front and a 4.10 rear. Dont ask my why, ask the previous owner..

So at this point I am thinking of doing a 4.10 in the front in a d30. Taking my time and adding discs at the same time.

I have a F134, but I can see in a few years dropping a 4.3 chevy in it..

I have 30" tires and can do 55 pretty well with the 4.10s, but hills are not so fun.

I have never had working 4wd on this jeep.. so I wonder how it will crawl/climb in 4wd with the 4.10s and the f134.

 

You probably will not like the 4.10's off-road even with a Chevy 4.3. To make 4.10's work you will either need a transmission with a low granny gear or an engine with a very large heaping of low end torque. As to the OP, like Ken suggested, go 5.38's and the OD. That would even work pretty well with a 4.3.

 

Good to know.. now I just have to find 1k for an OD.. lol

 

That's about right. My '54 3B, F-head, 5.38 & O/D...



I'm on a very slight downgrade in the video. Looks deceivingly steep due to the incline after the intersection in the distance. As long as the road is absolutely flat and there's no head wind, I could hold that speed all day. Guess my F-head didn't know it was tired until the very end.