Gear Ratio advice

[Automan2164]

If you go with 4.10s and find a junkyard front Dana 30 with them already installed (2.5L/5spd), you'll be way ahead of the game. :thumbsup:

 

:clapping:

 

Thats what I did! Have a '96 2.5L 5 speed XJ sitting in the garage with 4.10's under it.

 

Makes me warm and fuzzy inside when I think about those babies being under one of my MJ's one day... :yes:

 

Rob L.

[HOrnbrod]

IMHO, "ideal" ratios would be 3.73 for 30" tires (which was the plan when I bought the 3.73 gears), 4.10s with 31s, 4.56s with 32" tires, and 4.88 gears for anything larger than 32".

 

Carve the above in stone (or at least bookmark it). :D Exactly right, best all-around tire size/gear ratio setups. :cheers:

 

If you shop around, you can get a genuine Dana gear set and master rebuild kit for about $300; Yukon sets for maybe $50 less shipped. A reputable shop that specializes in re-gearing down here typically charges about $200/axle labor. There's a famous state-wide-known good old boy out of Birmingham who travels around the state on a semi-fixed schedule to various dealerships, 4WD shops, etc. and all he does is Dana diff regears, mostly Jeeps, and is always busy. That's ALL he does, he is very good, and has a 100% no questions asked guarantee. That's the type of tech you need to find, not some local yahoo who brags a lot. Ask me how I know. :doh:

[BLHTAZ]

I run 4.56 gears with 35" tires, 4.0L, AX-15 in our '95 YJ. I would not want the ratio any lower as it can start out in second gear most all the time. I will agree with Eagles scenario if you have an automatic transmission, but with a manual, I think those ratios are a little to low for the tire sizes.

 

For a combination vehicle (driver & play) I have always used 3.73 for 31", 4.10 for up to 33", 4.56 for up to 35", and 4.88 for up to 37". If the vehicle was off-raod only, I would step down a notch on all of thsoe ratios though. :thumbsup:

[HOrnbrod]

Agree maybe for the 4-speeds, but the AX15 5th gear ratio is 0.79; the AW4 O/D is 0.75. Still say it's the best overall performance vs. mileage setup Taz-man. :cheers:

[Eagle]

well the i thin i will get some 4.88 gears then but what will the top speed be? just wondering

With 4.88 gears and 32" tires, 70 MPH will be 2714 RPM.

 

With 4.88 gears and 33" tires, 70 MPH will be 2619 RPM.

 

The engine has a 5,000 RPM redline, but in overdrive with big tires, pushing a "brick on wheels" down the road, it's extremely unlikely you could actually get it up to the redline in top gear. But you should have enough moxie to get up over 100 MPH -- which IMHO is a helluva lot faster than anyone should be going in a 20+ year old Jeep that's lifted and riding on mud tires.

[Casper2000]

Eagle

Now that some one has started this for me I'm going to jump in and ask the same question.

With this LS1 and tb350 tranny 31" tires am i good with 4.10's myself.

Didnt mean to hijack your thread.

[Pete M]

I don't see why you'd have a problem. :dunno: I've got 30" tall tires on the rear of my Dakota R/T and I experience no ill effects (factory tires were 28-ish). :thumbsup: Offroad you may find that you don't need low range all that much, but experiment with it to see what works best for each situation..

[glundblad]

I don't see why you'd have a problem. :dunno: I've got 30" tall tires on the rear of my Dakota R/T and I experience no ill effects (factory tires were 28-ish). :thumbsup: Offroad you may find that you don't need low range all that much, but experiment with it to see what works best for each situation..

 

Believe it or not, the engine runs like a top. Very smooth except a slight idle problem I am looking into. But if I were to travel down the highway at 65mph and climb a hill, it will slow down even if I floor it. The truck came with 225 tires but I put 235 on it. My other thought is that perhaps the clutch is slipping due to a stunt from my younger days that my wife still brings up after 17 years :ack:

 

Do you think this is abnormal performance or should this be expected?

[88mjmanche]

thanks guys i think i will get some 4.56 gears and my 32 inch super swampers and will be set. and also sorry for the :hijack: but i think 4.56 will be way better because i don't do any highway and i olny do about 65 max any ways when i do go highway

[Eagle]

Believe it or not, the engine runs like a top. Very smooth except a slight idle problem I am looking into. But if I were to travel down the highway at 65mph and climb a hill, it will slow down even if I floor it. The truck came with 225 tires but I put 235 on it. My other thought is that perhaps the clutch is slipping due to a stunt from my younger days that my wife still brings up after 17 years :ack:

 

Do you think this is abnormal performance or should this be expected?

It's normal.

 

If the clutch were slipping, your RPMs would increase and you wouldn't have to shift.

[Pete M]

My 88 suffers from a distinct lack of power at freeway speeds. I haven't been able to dig into it yet, but my main suspects are a loose timing chain (I also suffer from horrific oil blow-by) and fuel delivery (possibly a failing pump or a bad fuel pressure regulator). Back in the day when the truck was a little 2wd DD and I was running 30s on 3.08 gears, the power was fine on the freeway but sucked taking off at stop signs.

[glundblad]

I took the comanche into the shop (yes, the dealer :shake: ). It has been running very well except for at idle. Then it was a little rough. I already replaced quite a bit. Rotor, plugs, wires, iac motor, o2 sensor, injectors cleaned. I was really running out of ideas. I was able to request a guy that had a 4.0 and worked there for a long time. He replaced the EGR valve and a solenoid vacuum switch whatever that is. It is smooth as silk now. She was able to climb hills just fine and accelerate while doing it. I was going 65mph+. So it looks like the gear combo I have is fine for city and highway use(although more would be better). What a relief.