[nj tj]

I have a 4cyl with 33s, and i agree that you have a jeep not a sportscar, i personally dont have the money to regear so i just take it for what it is....a JEEP! Its no big deal if im lagging on the highway cause im looking mean doing it.

[chadsmeltzer]

I know a few people that had JCR Offroad in Kalamazoo do it and no problems, average price. I think $1100 for both axles and parts.

[zband]

Thanks for the responses - but doing the math (Thanks Novak Conversions!)

at 70 mph with 4.88's the engine will be spinning at 2400RPM versus 2250 with the 4.56's. That being said, dont you think that the MPG will be better with the 4.56's? This is a daily driver that see's a lot of highway in Michigan.

[chadsmeltzer]

150 RPM's won't make a difference in MPG. Does that figure in OD? I have never heard of anybody with the 42RLE, 33's, and 4.88 complain once OD kicks in. If you have 4.56, OD might have to shut off more to make up the hill, which would be around 3200 RPM, where 4.88 might have the power to make it.

[robncar]

Originally Posted by zband

Thanks for the responses - but doing the math (Thanks Novak Conversions!)

at 70 mph with 4.88's the engine will be spinning at 2400RPM versus 2250 with the 4.56's. That being said, dont you think that the MPG will be better with the 4.56's? This is a daily driver that see's a lot of highway in Michigan.

It's counter intuitive but the lower gears may actually be better for MPG. You'll depress the pedal more to make up for the power loss with the taller gear.

Gear changes are more than RPM matching.

We add lift to our Jeeps to accommodate bigger tires, this places the body higher in the wind stream and increases drag. The larger tires have higher unsprung weight and increased rolling resistance. We also add additional weight, armor, etc. These factors must be mitigated to put the engine back into an efficient power band.

I daily drive the 6-cylinder, 4-speed auto on 35's and 4.88's. If I could have, if not for the limit of the D30, I'd be running 5.13's right now. I hit the OD off button every day on the street (mostly flat). 4.88's are the right choice with 33's and the 4-speed auto with it's 0.69 overdrive. You'll get power and efficiency all in one nice package.

[zband]

Having a tough time finding a place to actually put them on

DTS: $2700 labor and parts

Reider racing - 1700 for elockers , 370 for the gears. BUT they DONT install! referred me to other shop which will do it for about 600 (f+r)= $2600

Man this is getting steep, I thought it was going to land about $2000- 2300

NOTE: I talked to a service man at DTS. He said DO NOT go for the 4.88's because the strength of the Rand P is weaker than the 4.56 and it will wear out - is this true??

[Jerry Bransford]

Originally Posted by zband

NOTE: I talked to a service man at DTS. He said DO NOT go for the 4.88's because the strength of the Rand P is weaker than the 4.56 and it will wear out - is this true??

Total bull. That rumor was running rampant 10-11 years ago when the 4.88 first became available for the TJ but that proved to be completely unfounded. The slightly smaller diameter 4.88 pinion gear itself is actually more fully engaged than the 4.56 pinion gear is, plus the shafts themselves are essentially the same diameter. Too many of us running 4.88 gears, me included, on the hardest trails imagineable and no problems with the 4.88 gears whatsoever. The service guy you talked to a DTS is probably just repeating the same tired rumors he heard... ignore him, 4.88 works fine without problem.

Look at my website photos and then ask yourself if it looks like I baby my 4.88 gears. Plus I have over 90K (maybe >100K) miles on mine.

[chadsmeltzer]

From JCR Offroad...

Cost out the door:
We can get gears for your axles upon request, Gears plus installation is between $800-1100 for two axles depending on the axles you have. Please contact JCR for more information!

[thejafe]

Interesting thread. I always had my heart set on 4.56's but now you guys are making me rethink that.

[robncar]

Originally Posted by thejafe

Interesting thread. I always had my heart set on 4.56's but now you guys are making me rethink that.

Yep, I'd suggest you should reconsider with the 4-speed auto and 33's; 4.88's is the way to go.

[zband]

So is the verdict with gearing, in terms of gas milage going back to near original specs, are:

With 33's:
4 speed auto - 4.88's
5/6 speed manual - 4.56's

I just would like to make sure - I dont mind having to turn off the OD every now and then to get the gas milage back and I surely dont want to do this again if 4.88's actually consume more fuel on the highway, but with added pep!

Robncar your post does make sense. Ahh if only there would be a formula for this....

[robncar]

Originally Posted by zband

So is the verdict with gearing, in terms of gas milage going back to near original specs, are:

With 33's:
4 speed auto - 4.88's
5/6 speed manual - 4.56's

I just would like to make sure - I dont mind having to turn off the OD every now and then to get the gas milage back and I surely dont want to do this again if 4.88's actually consume more fuel on the highway, but with added pep!

Robncar your post does make sense. Ahh if only there would be a formula for this....

Yes, your chart looks correct... for the 6-cylinder.

Ya, no formula, but experience. It is something you only want to do once due to the cost.

I have a buddy that really overthought this. He did calculations, he pondered, he wouldn't even drive mine. He regeared to 4.56 with 35's. He was not really happy with the performance. He then drove mine, regeared to 4.88's (he has the 5-speed). It cost him $$$ but he now can see the light. He's poorer but happy.

I try to help folks, especially with the 4-speed auto, to not make the same mistake.

[Grewe02]

Originally Posted by zband

I would like to *finally * regear the jeep after running 33" tires and 3.73 gears. Mathematically I think 4.56 's should would nicely and give me back some MPG's. Since I'm at it I thought why not some lockers - so I'm thinking Eaton e-lockers (I'm kinda set on the selectable)

1. Where would you purchase gears and lockers ? (good deal?)

2. Im here in Lansing MI any suggestions on where I could get a good quality install, ie someone who is will to get the specs exact?

I didn't even bother reading the thread because nobody can ever agree on this subject. But my recommendation is to wait until you gain a tire size. Then go to 4.88s with 35"s. IMO you will be way happier.

[robncar]

Originally Posted by Grewe02

I didn't even bother reading the thread because nobody can ever agree on this subject. But my recommendation is to wait until you gain a tire size. Then go to 4.88s with 35"s. IMO you will be way happier.

The OP has the 4-speed auto. It's a different animal. Your recomendation does not apply, sorry. If he had a manual, I'd agree with you.

[Grewe02]

Why does it not apply? Do you have both a 4 spd Auto and a 5 / 6 speed manual? Have you driven both?