gear ratio

[bharris]

I have a 94 YJ with a 4.0 ,I am running 33-12.50 with a 5" lift,When I bought the YJ I was told that it had 4.10 gears, My problem is that there is no power in 5th gear doing about 75mph down the interstate Im only runing 2500rpm, and Im only geting about 15mpg,The motor only has about 20,000 on it sence it was rebilt, Any one got a segestion on a happy medeom gearing ?

[Old Fart]

Factory 4.0 is almost always 3.07's with the 5 speed. Should be a tag on the rear diff.

4.10's are a pretty good compromise for the 33's - if you can find a wrecked 4 banger YJ, swap out the D30/D35 (or do a 4.10 8.8 Ford rear)

[steelman]

bharris,

I'd definitely be interested in a verification of what gears you have. Right now I have the 3:07's with my 4.0L 3-speed auto trans, but am going to be putting 4:10 gears in next month (got a deal too good to pass up). I also have 33X12.50 tires.

Like Old Fart said, check the metal tag on your rear dif. It should be bolted on with two bolts to the drivers side of the dif, the tag is roughly 1/2" X 2" in size. I'd hate to hear that I'm gonna be hatin' the 4:10's <:mad:>

[aston]

I have a 94 YJ with a 4.0 ,I am running 33-12.50 with a 5" lift,When I bought the YJ I was told that it had 4.10 gears, My problem is that there is no power in 5th gear doing about 75mph down the interstate Im only runing 2500rpm, and Im only geting about 15mpg,The motor only has about 20,000 on it sence it was rebilt, Any one got a segestion on a happy medeom gearing ?

Sounds about right: 33, 4.10, 2500 = 75mph

http://www.4lo.com/calc/gearratio.htm

Play with the calculator to see the effect of 4.56 and 4.88 gears.

15mpg again sounds about right. I get 14.6mpg with the 4.0, 35, 4.56 on the highway.

[Mtbikbob]

Sounds about right: 33, 4.10, 2500 = 75mph

http://www.4lo.com/calc/gearratio.htm

Play with the calculator to see the effect of 4.56 and 4.88 gears.

15mpg again sounds about right. I get 14.6mpg with the 4.0, 35, 4.56 on the highway.

I must be doing something wrong....I came up with 59.9 mph. 1.0 in 4th. 1.0 in hi in the transfer case yes?

[aston]

I must be doing something wrong....I came up with 59.9 mph. 1.0 in 4th. 1.0 in hi in the transfer case yes?

nope ;-)

4th is 1

5th is 0.79

ax-15

[Mitch]

Well, as a comparision...

Stock 88' YJ 3spd auto - changed stock 3.55's to
3.73's on 33"x12.5" = 2500 rpm @ 70mph. Should have gone to 4.10's!.

Mitch

[aston]

Well, as a comparision...

Stock 88' YJ 3spd auto - changed stock 3.55's to
3.73's on 33"x12.5" = 2500 rpm @ 70mph. Should have gone to 4.10's!.

Mitch

Gearing is like ammo - you can never have enough ;-)

[Jerry Bransford]

For 33" tires and a 5-speed, you can't beat 4.56 for an excellent all-around gear ratio... both offroad and onroad. When I used to run 33" tires, I made the mistake of regearing to 4.10 and I hated having to downshift so often afterwards. I should have regeared to 4.56 when I installed those 33" tires.

[bharris]

thanks for all the information, I am going to pull the diff covers and make sure what gearing I have,The gear lube needs changed any ways.