Decisions! Decisions! Decisions?

And sometimes one makes the wrong one.:banghead: Reciently I bought a D44 rear and had it rebuilt with traction lock and 4.10 gear set withthe intention of using 31" tires. Now it seems the 31" requires a lift of about 3" to clear the fenders. Most people are fine with 30". If I use 30" tires then I think 3.73 gears would be more econimical on the highway where the XJ spend most of it's time. Now what should I do
. Do a two inch lift making it about 19.5'' measured at the front flair and 18.5 at the back or go to 3.73 gears and 30" tires.
Then the next question. Where I do I carry the spear :dunno: inside on the floor or outside? Roof or bumper?

TIA.

A stock full size spare will fit in the back where the spare sits now. the stock tire is close enough in size to use as a spare. Just move the curved bolt up to the next higher spot on the wall of the cargo area.

I have a 31X 10.5 in the stock location....the seat only latches on one side, but its fine.....

I also got a used spare so that the tread was worn off a little, so its not a true 31" tire.

stick with the 4.10s , you'll want them when you decide to lift another inch and trim the fenders to fit 31"s.
JMHO

peace

Keep your spare inside. If you stick it on the roof, it will kill your fuel mileage. Getting mine back inside netted me 2mpg improvement. Sound hard to believe? It's true.

Do the Budget Boost and go 31s and keep the 4.10s no matter what tire you decide on now. If you decide 30s now you'll do the 31s later and you'll be better off with more gear either way. Just because the engine spins a little faster doesn't mean you are using more gas. It is sometimes just operating in a more optimal torque range thus working easier.

HTH,
Crunch

I ran a bunch of #s this weekend, since I plan to either go with 4.10 or 4.56 on 30" or 31" It really just depends which axle/diff carriers I want to use, and how lazy/motivated I get in the swapping.

The difference in speeds vs RPM between 4.10 & 30" and stock (3.55 & 28") is pretty insignifigant... the taller tires & lower gears in 3rd gear(4th if a 5 spd) will be going 54 MPH @ 2500 vs 53 MPH with the stock setup. (So... by my #s, the stock setup is a hair lower...but that's assuming a stock tire size of 28")

My DD is presently on 205/70s (LOL blushing) and if I do in fact use my 4.56s on true 30", it'll be just a hair lower than I presently have..

Assuming is great, but also consider there will be losses through the drivetrain, and also consider that tire sizes are often optimistic on the + side...use your loaded radius at the driven wheel for a 'true' (or truer) # to plug into the formula.

I'd stick with the 4.10s since you have them in already.

My mother in laws xj is on 3" lift, 30" AT's and has 4.10 gears. It is a wonderful on road riding truck. I would not change anything except I would replace the 30's with 31's when they wear out.

Spare tire stays inside until you get anything larger than 33's.

Michael

My '88 MJ is currently running 31" tires and 3.73 gears. The overall final drive ratio is EXACTLY the same as stock tires and 3.55 gears. I run 2200 RPM at 65 MPH on the highway.

I originally bought the 3.73s to run with 30" tires, but my brother passed along a usable set of 31s so that's what I run. 4.10s would be much better with the 31s, though, and would definitely not be too much gear with 30s. Running 30" tires and 4.10 gears, you would be spinning 2428 RPM at 70 MPH.

Give it some time before you decide you hate it too. I'm running 4.10's with 31's right now with my 5-speed, so the jump from 3.07's was big to me. It was weird having the rpm's "so high" on the highway at first, but now that I'm used to it it's actually nice. I have power in all gears again. I calculate my mileage pretty precisely and with the gear swap I've lost .1 or .2 mpg, which is close enough to be the same.

I am running 3:55 gears to a AW4 with 31" X 10.50 GY MTR's and I get around 18 mpg with the 4.0L engine. A lot better than my TJ with 33's and 4:88's!

Thanks all. My major concern was about high RPM's and poor fuel milage. However, I would also like to spin the 4.0 another say 200 RPM on the highway to prevent the AW4 from gear hunting up those long hills. I will try the 30's first.