I have an 1986 CJ daily driver w/the 4.2 and 5 speed. It had the 2.72 gears and I re-geared it to 4.10 and run 31 X 10.50's and at 60-65 MPH it runs about 1900-2000 rpm's. I would if I was you cause since the re-gear I can use 5th gear.

BOOGER

"Sometimes Insanity and Genius walk the same side of the street"

 

You should not only regear, but if you plan to add a locker at some time, do it now too. Otherwise you'll have to pay labor to have the locker installed, but doing it now labor will be virtually the same for regearing and installing the locker as it would be for regearing only. Go with the 4.10 and a locker.

 

I also agree with the re-gear.

3.73 is the magic #....any ratio higher than that and you have to changer carriers.....so you might as well do it all at once....

I ran stock gears for some time with 31's....then went to 32's and it was really tough on both the road and trail to drive.....to get an idea of what it will be like....try starting out in second gear (ok...so you may have to use someone else's jeep to try it). Anyway, that is about what it will feel like.

4.10 Gears are perfect for 31-33" tires. While your at it, maybe throw in a Detroit Tru-track. It's very good limited slip that does NOT require a special additive to the diff oil. Great for every day use and does well on the trail...tire start to spin? Just give it a little brake and you will get more traction.

Don't forget...that if you do the back...you have to do the front as well.

 

Thanks guys for the info. How much do you think that the Detroit Tru-track will cost?

 

If you have overdrive, follow the advice and go to 4.10. If you don't have overdrive, 3.54 works well with 31's.

 

... Oh... and yes, you do have to regear both front and rear. Can you imagine if you regear the rear, and then lock in 4WD and attempt to drive with two gear ratios? Something will have to give, and it will likely be either one of the diffs, or the transfer case.

Also, agreed, if you're going to put in a locker, do it now. The Detroits are good lunchbox lockers and will do you well. Are you asking about the cost of the locker, or the cost of the locker and labor to install?

 

Cost of the locker is what I'm looking for. They seem to be a wide range on cost and types. I'm going to call the shop first thing this morning and have them start the re gearing and depending on the cost of the lockers, I might have them done later. In fact I'm not sure that this shop will install lockers. I might have to trailer the jeep to ORW and have them do it.

 

A detroit Truetrac for a 30 spline 44 w/ 3.94 or higher (numerically) gears is gonna cost right at about $500. If the shop can install gears they can install lockers. The ring gear bolts directly to the Truetrac, as is replaces the entire carrier. The shop shouln't charge any extra for the locker install as long as they haven't already set up new gears.

 

I'm in the process now of taking my jeep from the shop that it's at and taking to ORW and have them finish the repairs and upgrade. I agree that it should be a simple put the part and go but for some reason it's not happing.

 

Interesting?

 

Definitely, think about regearing.

A few thoughts some of which have already been already been pointed out, but are repeated to show agreement and for the sack of completeness.

1. If you regear you need to do both, front and rear.
2. If You wish to re gear and can afford to do so now, this is a good time to do so.
3. If you plan to add a locker or LSD (Limited Slip Differential) to the front or or rear or both the best time to do so is when you re gear.
4. If you can not afford to re gear both front and rear ends now, try draining and refilling with clean gear oil. This may not stop wear but it will reduce it, and new oil is $10 to $50 in oil and what ever they charge you in labor, (should be less then 1 hour total). Where as new gears will be $150 for gears, plus $90 for install kit, plus labor (4 to 6 hours) and that is per end. So a re gear will be over $1000 for both front and rear. It should be noted that the numbers given for re gear are somewhat optimistic.
5. The correct gear ratio for you will depend on what you plan to do with the jeep and what transmission you have and what transmission you may plan to switch to in the future. You should be complimented for doing a good job of describing your plans for use of the jeep, but you do not mention what model or even type of transmission you have (auto or stick).
6. The Ideal gear ratio is but one part of a larger equation, that includes: Engine size and type, transmission type and ratios, transfer case ratio, tire size and last but not least expected use and expected economy verses off road ability of the jeep.

Okay, most of the above is simple enough, and seems to be coved often on internet boards but points 5 and 6 need a little additional explanation. However I need to get soem sleep tonight so I will add to this post in the morning.

 

Good points!!

The Jeep will be a daily driver with weekend 4x4 on trails. I don't want a rock crawler. I don't plan on going above 31' on the tires and at some point the jeep will get a 2' lift. Not sure yet what I have for a transmission, I think it's the T-4? The jeep is a 4 speed stick with the 258 IL6 that I rebuilt last summer. JeepDawg had a good point with the gear ratio upgrade. I think I'm going to put in the 3.73 front and rear with a Detroit Trutrack in the rear diff. I don't have the cash to put the Trutrack in the front diff at this time. Maybe at some point before summer I can put the Trutrack up front.

 

I'm sure some of the board members have 3.73 gears laying around their garages that would part with them for cheap. Put a "wanted" bulletin for 3.73 ring and pinion on this board and see what response you get.

 

Why not spool the rear and put the true track in the front?

as for 3.73 I throw them away regulary what rear do you have?

 

Not sure what you mean by spooling the rear?

I'm running a dana 44 rear and a dana 30 front

 

Spooling locks the dif, providing no differentiation at all. This would be fine on a dedicated trail rig or on a street driven Jeep that only goes in a straight line. However, when you go around a corner and the inside wheel wants to turn slower than the outside wheel, a spool can be troublesome. I would not recommend a spool for a daily driven rig.