Used Axle Gear Swap; Good Idea/bad Idea

[CRF136N]

OK, so I am pretty confident in most every mechanical aspect of these trucks but differentials are totally foreign to me, that's why I ask.  I attempted the pinion bearings in my old dodge once and it was a fail (but I think I realized what I did after the fact in regards to the yoke nut torque and could probably do it right the second time...but that how ya learn, right?)

 

Here is what I am working with; this '89 mj I just picked up has the 3:07 gears in an open D35 mated to the ba10 5-spd; and of course the d30 up front.  I upped the tire size from 205/75-15 stock to a 235/75-15...which did not help its getup-and-go with the renix power plant (but sure looks a whole lot better!).  Being my super clean low mileage 'barn find' of a manche, I do not have any plans to hack into this truck in any way as I want to leave it as clean and stock as possible...but as with anything any opportunity for an easy minor improvement; or an upgrade after a part failure is justifiable to me.

 

I have an '87 xj with a LIMITED SLIP 3.55 d35 in the rear (and d30 in the front).  I am just getting this xj buttoned up enough to sell; its not worth much but I can maybe squeeze enough out of it to justify the effort (and its getting all the old parts I have lying around and I'm keeping all the new stuff I put on it!).  Seeing as I am planning on pulling the axles apart on the manche anyway to replace the pinion and axle seals and replace the old oil, it wouldn't be much additional effort to pull the ring/pinion and swap for the slightly higher gear ratio...being an otherwise perfectly good d35 right now, as the rule of thumb goes with these cruddy d35 axles I'm not interested in buying new gears for it...if it fails I'm finding something better, but with 85k on its going to be awhile.

 

So see where this is going?...I sure wouldn't have a problem swapping that limited slip 3:55 rear gear set into the manche (and the front to match of course) giving my nice pile of an xj some 3.07's, should really make it a turd with the aw4 but whatever, I am sure some high school kid would love it as a first vehicle and will never know the difference...besides its now sporting the manches old 205/75-15 tires :)  On the other hand I suspect the 3.55's would really help the manche out without compromising the fuel economy too bad as the larger tire should help offset the difference.

 

Swapping axles is too much work with cutting/welding rear perches plus the front axle is always a gangly fun disaster I just don't want to mess with right now.  If this is a realistic possibility of just swapping the gear packs while I'm in there I'm all for it; I just don't know if its a bad idea to swap used gear sets between axles like this...thoughts?  If not, I am ok with the MJ as it is; would just be nice to make the gears a little more useable in it without having to always downshift and rev the motor out just to get to the top of an incline in the road.

 

Thanks for any info!

[Bornindesert]

If it was me and I didn't want to buy new ring and pinions, I'd swap gears in the D35's and axles for the D30's. I'd also take the time to properly set up the D35's, meaning setting backlash, pinion pre-load and mesh. You'd need some new shim kits and a hand full of new crush washers. BTW, torque range for the pinion nut is something like 250 ft-lbs up to 500 ft-lbs (don't quote me, I'm just saying its A LOT of TORQUE). Setting up the D30's properly is much more work in my opinion, have to deal with carrier preload, pinion depth, backlash, pinion pre-load and mesh. It's a job much better suited for set-up bearings which would mean buying at least one master install kit. Not impossible to do under the vehicle, but much much easiler to do on the bench, which means pulling the front axle anyways. 

[CRF136N]

Meh; already sounding like too much work lol. Suppose I should have mentioned as I forgot...the limited slip rear d35 in the xj is from my '96 police package xj (swapped 'em cause the '87 originally had a d44)...but I wouldnt imagine it would make any difference...the 87 still has the original front axle. All this lash/shimming/etc is sounding too involved...or is it easier than it sounds? Neither of these are daily drivers so I'm not in an hurry but would be nice to sell the xj asap...wanna use the $$$ I get for it for a spray in bed liner on the mj :D

[Bornindesert]

I'd say it's definitely not easier than it sounds, which is why many just swap another axle or have a shop set up the gears. If you have some patience and take the time to learn the process, than it's just like rebuilding an engine or trans for the first time.

 

You'd also need to check and make sure the later model '96 D35 is not a C-Clip rear, the carriers don't interchange...I don't think anyways. The '87 D35 would be Non-C-Clip rear, if it's the stock axle. So, if they don't you wouldn't get the limited slip into the MJ axle. The gears probably would interchange but you'd have to check that out too.

 

Plus, agree that just pulling the shafts out of a D30 that's been on the truck for 25 years can be a royal PITA. That's one tough NUT!

[mvusse]

I would swap the axles. D30 is a bolt in affair, and shock mounts/spring perches for the rear axle are less money and labor than a gear change, even if the carriers do swap between C clip and non C clip.

 

Yes, you already have the gears. But you will need two master install kits, a set of set-up bearings and a number of pricey new tools you will likely never use again.

[CRF136N]

I'm convinced, not gonna waste the time. Was just a random thought as I'm stealing any half decent parts off the xj before I sell it; thanks for the replies...not that I don't want to learn axles as having the jeep disease and going through countless jeeps its a good skill to have, I just have too many other fires to put out this summer...maybe next summer :)

 

Thanks again!

[CRF136N]

...although that limited slip rear end is kinda nice for driving in the snow ;)

[Bornindesert]

I'm sure something else will pop up before snow falls, in the mean time think about how much more time you'll have to drive the Manche this summer!

[CRF136N]

I'm sure something else will pop up before snow falls, in the mean time think about how much more time you'll have to drive the Manche this summer!

Prob not gonna be rackin up the miles on the mj too fast, its more a weekend cruiser for hauling my dirtbike around.  The police package '96 xj is my next burning project...and toy...

as it sat a year ago after buying it for $200 :)

 

As it sits today, after WAY too much time and money; just can't stop but in too deep now, gotta keep goin!   :doh:

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Just Empty Every Pocket...amen.  Why the HELL did I ever buy a jeep as my first car back when I turned 16!?!  They need to have minimum requirements to own one; perhaps a college education in economics to show financial understanding and responsibility and come with caution waivers that must be signed by law stating the addictive nature and financial/family ruin associated with the addiction...not to mention the acceptance of kitchen tables becoming work benches and spare bedroom closets becoming parts storage units...yup, been accused of them both. . :MJ 1: .

[CRF136N]

HAHA; that little smilie driving the Comanche really is me, thought it looked familiar...I just need some black rims on my MJ and everything else from the paint to the decals match...

. :MJ 1: .

 

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:rotfl2:

 

 

[Biotex]

I'm going to be doing a write up very soon on a step by step to install a set of used gears in a D30.

Honestly, it is easier to just change out the whole axle IMO, but i'm very remote where I live, and no parts available. At least I have all the tools needed.