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-   -   what are my diff gear ratios? (http://www.wranglerforum.com/f218/what-are-my-diff-gear-ratios-252905.html)

n2trucking 07-01-2013 11:46 AM

what are my diff gear ratios?
 
1990yj 4.2 inline 6 with AX-15 5 speed NP231 T-Case. 31x10.50-15 tires
Dana 35 up front and Dana 30 in back.

I was wondering if anyone would have any idea on what ratio is on my differentials?

At 55mph in 5th gear the rpm's are running at 1700-1800 hundred. It's a little hard to tell with factory gauge. And in fourth gear at 55mph the rpm's are at about 2300-2400.

I'm thinking it's 3:07? The factory specs say 1989-1990 with inline 6 there were 3:07 3:54 3:73 options.

Now I know I can just take off the diff cover and see but I'm avoiding that for the moment because it would be nice to just find out without having to do that. There aren't any tags on my diffs telling me what I have. The covers have been off before but not by me.

Now I would like to run no bigger then 33x12.50-15 tires and 4" lift and was wondering for the moment would my axles and ratio handle this. Not an extreme off roader right now.

My engine has been fully rebuilt with all the after market stuff you can think of put on there and no emissions and bored over 0.30 and I had it on a dyno and got 132hp and 234 ft. lbs. of torque and running on 93 octane.

Would a simple 4:10 ratio and axle housing swap from a 4cylinder wrangler solve any issues I might have? Right now my jeep is doing great with the 31's.

I'm just trying to keep the axle setup just simple and still road worthy. Thanks.

Norcal_Chris 07-01-2013 12:42 PM

Pull the covers and find out. Its good to do it anyways as a preventative thing and to check things out. Everytime I pulled my d35 cover I would remove the chunks of metal out of it.

I never trust what the factory said or what should be there because these jeeps are ild, and have changed hands and changed parts many times.

33s would probably be fine. You may not be able to hold 5th all the time.

AllMudd 07-01-2013 01:39 PM

Add on from the previous post. Dana 30 in front and Dana 35 in the rear unless you have rear wheel steering. Dana 35 is the rear axle not front.

roadyrob 07-01-2013 02:31 PM

4.10 gears out of a 4cyl. will be great for 33" tires.
I assume your dyno numbers are on a chassis dyno, if so they are excellent! good job!!
what are you running for a carb and distributor? cam?

n2trucking 07-02-2013 01:35 AM

Quote:

Originally Posted by AllMudd (Post 3916885)
Add on from the previous post. Dana 30 in front and Dana 35 in the rear unless you have rear wheel steering. Dana 35 is the rear axle not front.

yes sorry I mixed those up.

n2trucking 07-02-2013 01:58 AM

Quote:

Originally Posted by roadyrob (Post 3917075)
4.10 gears out of a 4cyl. will be great for 33" tires.
I assume your dyno numbers are on a chassis dyno, if so they are excellent! good job!!
what are you running for a carb and distributor? cam?


yep. There was a local car show where I live and I heard they were having dyno contest and of course I just wanted to see what I was doing.

0.30 overbore and comp cam and lighter weight, higher compression pistons and rods and a new crankshaft. all the machine work was done at a Napa auto parts store and all the parts was ordered through them.

The top end is fully rebuilt head with overbore valves and offenhauser intake, HEI distributor and 8.5mm wires and Autolites Double Platinum
MC2100 carb with 49F jets, K&N filter and still running on the mechanical fuel pump but of course it's a new one. NO EMISSIONS AND NO ECM running engine. :punk:

n2trucking 07-02-2013 02:00 AM

Quote:

Originally Posted by Norcal_Chris (Post 3916708)
Pull the covers and find out. Its good to do it anyways as a preventative thing and to check things out. Everytime I pulled my d35 cover I would remove the chunks of metal out of it.

I never trust what the factory said or what should be there because these jeeps are ild, and have changed hands and changed parts many times.

33s would probably be fine. You may not be able to hold 5th all the time.


ok great thanks. Ill prolly just run new 33x12.50-15 until I com across some 4:10 off of a 4 cylinder.

Is the 4:10's still Dana 35 in the back and Dana30 up front?


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