Axle Gearing

I’m building a set of Scout d44s for my cj7 and I was planning on using some 4.56 gears in them that I have. It was also going to put a D300 transfer case in with the stock low range gears. Now I am thinking of putting a 4:1 low range kit in the 300 and some higher axle gears in the 44s. I have an ox locker that is for 3.73 and down and it would like to run 35” tires eventually. Would 3.73s be too high for street use and the big tires or should I go with 4.10 thick cut gears? I would like it to be streetable and have a good low range ratio.

 

Right now I have a t18 with 6.32:1 first, D20 3.73s and 34x10.5 super swampers tsls and it does okay on and off road. I’m leaning towards 3.73s in the D44s.

 

I use this for numbers.

http://www.grimmjeeper.com/gears.html

Ron

 

Thanks, that is super helpful to see what the on road speed and engine RPM would be.

 

I ran those 35/15-15 superswampers 30 years ago in a scrambler with 4.10’s, T176, D300 and a swapped in 304, cam, 4bbl. It was ok street and mild off road, but a dog with the snowplow attached. I would go 4.56 if you have the option.

 

I think that much tire will require a lot of torque and hp.
You’ll want a 304 @ 4.10 minimum or the street performance will be poor.
I wouldn’t go higher gears than 4.10 even with an AMC 360 and go 4.56 max if you have a 258.

 

360 v8 with an RV cam.

 

Yeah 35” should be fine with a 360 engine.
I’d suggest 4.27’s or 4.09’s.
I’d probably opt for the 4.09’s
Either ratio gives you a decent sized pinion gear.
With 4.09’s the max hiway efficiency should come around 2400 rpm @ 60 mph.

 

And that’s the case break too.

I think 4.10 will be fine.

 

The torquey Buick 350 in my 71 is happy with 3.73s and OD with 32s. It loves loafing down the highway at 1800 rpm and 60mph.

It really depends on the engine. I would think a 360 would be fine with 3.73s.

 

With 3.73’s it will be running 67 mph at 2400 (cruising) rpm.
I think that engine can handle that but honestly idk.
I’d opt for skinny 35’s if I tried it

 

I'm runnin a 360 with 3.73's and I like the combination. I just recently put Elockers and new gears in both ends and didn't change the ratio, however I'm runnin 33x12.50's.
The Novak Guide to Gearing & Gearing Math for Jeeps (novak-adapt.com) I commonly use the Novak chart

 

I ran 33’s on 3.73’s in my 258 powered cj5 for years. I bumped up to 35’s a few years ago (bfg km3) and am still reasonably happy with performance. At some point I’ll probably do 4.10 and actual lockers but it’s low on the priority list. She goes down the road well and Still crawls reasonably well with the t18 and 3.15 geared Dana 20. That said she rides the trailer to the trails so I can’t say how well it climbs hills on the freeway although I don’t recall it being too bad in Moab.

 

I want to go with Q78 super swampers, which are basically 35x10.5.

 

With 3.73 gears and 35's and going 70, cruising rpm is 2500, which I feel is high enough in the RPM range to go up hill, but not too high to be screaming. 4.10's bring it up 2755 RPM, which I guess isn't terrible either. I do live in a hilly area. It really is a coin toss.

My F550 is at 2500 rpm with overdrive, 4.56 gears and stock size tires.

 

Yeah it also depends on how actual fast you like to drive on hiways.
You obviously have a big enough engine for power on hilly roads.
And the skinny 35’s should easily be do-able,
If the 360 engine is built as standard.then I would expect maximum “g” forces (aka torque) to be somewhere around 2400 rpm.
What do the dyno charts say about the 360 engine ?

 

I decided that I am going to go with 3.73. I was driving it yesterday and in low range, I forgot I was in 4th and it was basically idling down the road. It does have some very good torque.