Never done this, wanna do it right but dont know how!

[XJs4Ever]

My 89 has 307's and I just aquired a set of 3.55's front and rear. Ring, pinion and carriers and even a complete spare front D30 with all the steering components. Mechanically I have no reservations that I can regear these axles but I have never set backlash and don't want to lunch the diffs in the first outing.

I can't pay someone to do it and besides dammit I want to learn this myself. Any help is mucho appreciado. The 307's were fine when it had P225 tires on but with the 31's it lost alot of power/mpg. Eventually I'll fine sone 3.73's in the boneyard but 355's are everywhere and I got three sets for free. They can only help and from what I've heard it makes a huge difference.

[JeepcoMJ]

most of us won't tackle a regear.

 

we just swap axles. it's actually cheaper.

[project88mj]

hey i got 3.55 and i think that they hold the motor back so i am going to swap in an axle that has 4.11 in it already or just put them in myself as long as you take your time maybe ask another knowldgeable gear head if it looks good to him. (some day ill have a dana70 in the rear and a dana60 in the front and about 500hp turning 38s)

 

i hear that they are not the best for long highway drives but they are do-able,

 

in the city and around town as well as on the trail i hear that they are the best for a truck our size.

 

:yes:

[Pete M]

I hate 3.07s and I feel your pain Rick, but regearing is one of the few things that even I won't do. It's a mix of science and voodoo and if it doesn't come out right, you can end up with a noisy axle or even a burnt up axle. Is your MJ your daily driver?

[Eagle]

Backlash is only part of the issue -- setting the pinion depth for proper engagement is perhaps even more critical. That's hard to do without the proper measuring equipment, or lots of gear-marking compound and trial-and-error.

 

Second point -- used gears are almost always noisy, because there ain't no way you will ever get them set up exactly the way they were run in before. You may have them set up "correctly," but they won't be the same.

 

Lastly, it's just not worth the effort to go from 3.07s to 3.55s with 31" tires. I ran 31s with 3.73s. The overall final drive ratio works out to exactly the same as 3.55 gears with stock tires. So by going to 3.55s with the 31" tires, about the best you'll manage to do is get back somewhere in the area of stock 3.07 gears and stock tires. You probably won't have much luck finding 3.73s in a junkyard, because that wasn't a common ratio. But most 4-banger XJs and MJs had 4.10s, and that's the optimum ratio for running 31" tires. My humble advice is to not waste any time, effort or money on the 3.55s. Just look for a set of JY axles out of a 4-cylinder XJ or MJ and throw those under your truck.

[project88mj]

:agree: :agree: :agree: :agree: :agree: :agree:

 

I'm looking I'm my area no luck yet but i will not give up :fs2:

[mvusse]

To setup the gears yourself you will need some specialty tools, like an inch-pound (not foot pound) torque wrench to measure bearing preload, a dial indicater and various mounts to measure backlash and a spreader for a D35 to physically stretch the housing lengthways to remover/insert the ring gear assembly. You may be able to make your own out of structural steel scraps like square tubing or angle iron.

 

The only way to get the gears set up right is to insert, check measurements, take out, add/remove shims, repeat. Since the pinion bearings are pressed on, it might help to take an old set and clearance them with a die grinder so they just slide on/off. Once you have the correct set up you press the new ones on. For that it may help to "bake" the bearings on an electric skillet and keep the pinion shaft in the freezer for a few hours.

 

Get a bunch of crush sleeves for the pinion since they can only be used once, and each try is a use, and at least one tube of gear marking paint to double check the pattern when you think you have it right.

 

I have done it under a vehicle before and do not recommend it. Put the axle on a work bench.

 

It's not rocket science, but it is very time consuming and a royal PIA. That's why most people pay a shop to do it, and why shops charge as much as they do.

 

I have done it three times. Will I ever do it again? Probably. Will I be cursing myself and promising (again) to pay someone next time? Definitely.

 

And never EVER get used gears unless you swap the entire axle. A new gear set can be had for ~$150

[DirtyComanche]

It's not hard to get them right, but it can be a huge pain. And you have to understand all aspects of what you're trying to achieve. Also, you're going to want to do it with the axles out of the vehicle. Unless maybe you have a post lift in your garage.

 

The problem with a dana axle is that all the shims go under or behind the bearings. So to change the shimming, you have to press the bearings off, then back on again. Which can be a real pain. One trick is to make 'setup' bearings by taking a set of brand new bearings and hogging out the races a couple thou so they are no longer press fit. Then to change the shim setup you can just slip the bearings on and off by hand. Once you get the shimming right, you press on a set of good new bearings... And it should all be exactly the same as it was with the setup bearings.

 

That said, I did a toyota third, and it refused to be the same with the setup bearings as without. It was a huge pain. I won't do anything on a toy now. Part of the problem may have been the setup bearings were not the same brand as the final assembly bearings. It should not matter, but I had SKF auto bearings for the setup and Timkens for final assembly, and I don't trust SKF auto bearings as they are made off-shore. Their aerospace bearings I don't mind, as they are still domestic...

 

Another thing that can be a pain with a dana axle is you might not be able to remove the carrier without a housing spreader. I have a D44 lying in my garage that regardless of how much prybar+swearing I applied to it, it would not give up the carrier. So, yeah... I probably could have got it out, but I wasn't in the mood.

 

Used gears, as Eagle said, aren't the best idea. You can make them quiet, but it can be hard. It depends on what shape they're in. Basically to be quiet you have to get the contact pattern under load the exact same as it was before. Yet, the BL still has to be in spec. If the origonal pattern sucks, you're hooped. And you might not be able to replicate the old pattern easily... If it's trail only, it doesn't matter.

 

 

However, I think with gears, it's a 'if you have to ask, you probably shouldn't' sort of thing.

[Redramman]

Its better to have lower gearing(higher ratio number),than to high.here is a cool tire/gear ratio chart.

http://4lo.com/calc/geartable.htm

[Redramman]

This site has alot of info downloads and sells tools and parts . The big square metal thing is the diff spreader. Not many people do their own gears.

http://www.ringpinion.com/ContentFrame. ... b_Done.inc

[XJs4Ever]

Well I refuse to subscribe to the opinion that going from 3.07 to 3.55 isn't worth the effort thats ridiculous and there are no 4.10s [whats a 4.11?? :huh???: ] to be found in these boneyards around here. 3.73's are up for grabs occasionally tho. Also no MJs in the junkyards either and an XJ rear is too much of a pain in the arse to swap into a Comanche. Nah, sorry but I'm stickin to this plan. I have one guy I traded a 48" hi-lift jack for a chainsaw who said he'd do my gears for $100 per end, axles out so I will contact him and set it up. I'll buy the beer and he can show me the deed. I'm an F.A.A. licenced aircraft airframe and powerplant mechanic and I THINK I can handle it with the training but like everything else you need to be taught how not to pee on the toilet seat before you learn to lift it up first - same $#!t here. If it fails - I will learn what failed and try again but I never quit before I try.

[Pete M]

Depending on what axle it is, dividing the ring gear by the pinion gear can give 4.10 or 4.11. Essentially they are the same thing though.

 

Don't be getting your panties in a bunch there Rick. :cheers: The guy are only trying to help. The facts that you're an aircraft mechanic and you'll be getting help from someone who knows gears were not included in the original post. Plenty of Jeepers have tried regearing on their own, and many many have failed. Some horribly so. We're just looking out for ya. :thumbsup:

 

As far as I know, XJ rear axles only need new perches burned on to go under an MJ.

[Redramman]

:agree: Check out the link to Randy's ring & pinoin that I put in a couple posts up ^

[Eagle]

Well I refuse to subscribe to the opinion that going from 3.07 to 3.55 isn't worth the effort thats ridiculous

No, it's not "ridiculous." It's pretty well accepted Jeep lore. Of course, how valuable your time and effort is to you may be different from how valuable my time and effort are to me. It's a LOT less effort and time to add a pair of perches to an XJ axle (or even to burn or grind off the originals and relocate them) than it is to set up a differential.

 

As to the worth of the results; I'll just post the figures and each reader can make their own decision. These figures were all derived using actual tire manufacturers' revolutions-per-mile from their web sites or sales brochures, so there's nothing theormetical here. And to avoid differences due to the several overdrive ratios used in the XJ and MJ over the years, I'll post only the 4th gear (1:1 ratio) numbers.

 

3.07 gears / 225/75R15 tires:

26.75 MPH/1,000 RPM

60 MPH = 2241 RPM

 

3.55 gears / 225/75R15 tires:

23.21 MPH/1,000 RPM

60 MPH = 2584 RPM

 

3.55 gears / 31x10.50R15 tires:

24.93 MPH/1,000 RPM

60 MPH = 2407 RPM

 

3.73 gears / 31x10.50R15 tires:

23.65 MPH/1,000 RPM

60 MPH = 2536 RPM

 

4.10 gears / 31x10.50R15 tires:

21.51 MPH/1,000 RPM

60 MPH = 2788 RPM

 

You want to go through all that work to make a ratio change that's about 15-1/2%. The tires you're running are 6.8% bigger than stock (in terms of actual revolutions per mile, which is what counts), meaning your net improvment for all that work is going to be 8.7%.

 

Maybe that's worth it to you, but having driven and wheeled 31s with 3.73s, there's no way I'd even consider doing 3.55s. Those who have been around here may recall that the reason I ended up with the 3.73s was an accident anyway. I had done the numbers, and I bought the 3.73 gear sets with the intention of installing in my Cherokee to run 30x9.50 tires. Then a Comanche with a 4" lift followed me home. My brother gave me the old 31x10.50s off his Nissan. The MJ had 3.07s, which sucked predictably with the big tires. Rather than buy another set of gears, I just threw the 3.73s into the MJ. They were fine on the street (about like 3.55s and stock tires, as I said above), but not enough gear for wheeling. 4.10s would have been optimum for wheeling, and still very good for street.

 

But ... do what you want to do. It's obvious you didn't come here to ask for advice but to tell us how much you know and how little we know, so ... enjoy the work.

[Pete M]

No need to fight here guys. There's some opinion in there when it comes to seat of the pants "that was worth it" conclusions.

 

I went from 3.07s to 3.55s in my 88 and it was a world of improvement with the 30" tires. But I didn't pay a penny for the upgrade. The pennies I spent (a lot of them) went to replacing the Dana 35 I just blew up with a Dana 44 (so that exploding thing wouldn't happen again). The gearing improvement was a side-benefit because I didn't really know any better at the time. If I was to do that over again, I'd have gone to 3.73s or 4.10s. But then, the truck was just 2wd at the time and so was only half the cost of a 4x4 to regear. But having said that, I was still much happier with 3.55s over 3.07s.

 

Don't forget to factor in the cost of new bearings and seals. Oh, and I second the Randy's ring and pinion website. Lot of tech on their site.

[mvusse]

4.10 gears / 31x10.50R15 tires:

21.51 MPH/1,000 RPM

60 MPH = 788 RPM

 

Ummm, 2,788 RPM maybe?

[HOrnbrod]

Well I refuse to subscribe to the opinion that going from 3.07 to 3.55 isn't worth the effort thats ridiculous and there are no 4.10s [whats a 4.11?? :huh???: ] to be found in these boneyards around here. 3.73's are up for grabs occasionally tho. Also no MJs in the junkyards either and an XJ rear is too much of a pain in the arse to swap into a Comanche. Nah, sorry but I'm stickin to this plan. I have one guy I traded a 48" hi-lift jack for a chainsaw who said he'd do my gears for $100 per end, axles out so I will contact him and set it up. I'll buy the beer and he can show me the deed. I'm an F.A.A. licensed aircraft airframe and powerplant mechanic and I THINK I can handle it with the training but like everything else you need to be taught how not to pee on the toilet seat before you learn to lift it up first - same $#!t here. If it fails - I will learn what failed and try again but I never quit before I try.

 

Hey Rick, I have to chime in here. When I went to 31" tires, I immediately realized I needed to regear. I had 3.55s (have the AW4) and decided to go to to 4.11s. And I agree with the previous posters, 3.55 gears are too tall for 31" tires. They will be an improvement over your 3.07s (anything higher is an improvement), but not much of an improvement and you won't like it for long. I wanted to do the gear swap myself too. A friend has a lift, so I picked up a set of Yukon 4.11s, a master rebuild kit, and went to work. To make a long story short, the only way I could get the pinion depth correct was by reusing the crush sleeve, which was wrong. I simply could not get the new crush sleeve to crush. I also ended up reusing the same pinion shims as they seemed to be closest to right. Drove it around; the gears were quiet, but after a few miles I developed vibes between 35-50 MPH when accelerating. After eliminating EVERYTHING else (driveline angle, tranny mount, u-joints, driveshaft, tires, steering, suspension, etc. etc.), I finally realized I must have flocked up the gears. I brought it to a shop, and that was the case - I had screwed up on the preload setting, among others. And I still don't know how. I'm not ashamed to admit it, and I did learn a valuable, although expensive, lesson. NEVER AGAIN! Period. So try it yourself if you must, maybe you'll be luckier than I was. Hope so. And I highly recommend you do not use 3.55 gears. Go to 4.10/4.11 (whatever) at least. It seems to be the ideal ratio for great acceleration and fuel economy. My 2 cents Rick-man.................

[project88mj]

while we are on the subject for those of you who had you gear work done at a shop what was the total cost: gears and labor costs included please.

[Eagle]

4.10 gears / 31x10.50R15 tires:

21.51 MPH/1,000 RPM

60 MPH = 788 RPM

 

Ummm, 2,788 RPM maybe?

Ummm ... maybe.

 

Dang typos ...

[Eagle]

while we are on the subject for those of you who had you gear work done at a shop what was the total cost: gears and labor costs included please.

Trust me ... you don't want to know.

 

When you find shops offering to do it for $100 an axle ... just remember, "You get what you pay for,"

[project88mj]

yeah i want to know (thats kinda why i asked) :fool: :thwak:

[DirtyComanche]

I think book time is like 6 hours an axle... Starting from a roller.

 

Dunno what shops charge out there...

[project88mj]

book time? :hmm: starting from a what? :huh???:

 

sorry I'm a bit of a :dunce:

[DirtyComanche]

Most autoshops don't bill the actual amount of time it takes to do the job, but rather the amount of time written down in some almighty 'book'. This way a fast mechanic makes more money, as he can work 'more hours' than there is in a shift...

 

And a roller, as in, it just rolled in... Like, drivable vehicle.

[Pete M]

Sometimes you can get a better price if you bring in an axle separate from the vehicle. That way it doesn't occupy a valuable lift spot.