6 posts in this topic

If you read this Moses, many thanks for your Dana 30 rebuild article, it's the only one I've found that helped me.

Here is my problem in a rather large nutshell. 1995 YJ, 2.5 5spd. I had an axle seal leaking and bad lower ball joints so I figured it would be a great time to upgrade to 4:88 gears and 4340 axles since I am rolling 33-12.50's. I opened up the diff to find a recent but very poorly installed 4:56. The caps were on upside down and it had about .100" backlash so I am essentially starting from zero. The carrier bearings appear to be original so I am fairly sure the shims are close but I am making a set of test bearings for all positions. There were no shims behind the forward pinion race and only the slinger behind the bearing, probably the culprit of the massive backlash. The pre-load shims are another issue. It appears the installer used all the shims he had and all that were on it originally. The original shims (determined by some discoloration) stacked to .057", He or she added another .041" to stack out at .098". I can do all the setup and the new gears have the pinion depth marked so I know what to shoot for, my question is what ballpark the pre-load shim pack should be in to start the setup? If I read correctly, the torque for the pinion nut is 160-200 ft/lbs so I know if it gets too tight before I hit 160 there are too many shims and if it hits 200 and doesn't have enough pre-load, not enough shims. I would just like a good spot to start. I am using a Motive gear set if that makes any difference. Thanks in advance to whomever might be able to help. I'm sure the Dana 35 in the back is in similar condition so any help will be greatly appreciated.

I would also like to mention how awesome it is to find a forum that is just simple and to the point without all the smells and bells to stagger my poor old Dell to a standstill!

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Mudbullet...Glad the article works well.  You're in a dilemma here and need to go with your test/used (reasonably good condition) bearing approach.  Spend time relieving the old bearings' inside bore sizes enough to allow the bearings to slide onto the pinion shaft and carrier flanges with even finger pressure.  Keep these inner bores concentric, no looseness or bind, when grinding or sanding the bore.  

I've found that inexpensive 1/4" shank drum sanding discs from Lowe's or Home Depot will work as well as arbor grinding stones.  Course works best on bearing steel, finer may be useful for polishing/finishing.  Expect sanding paper to go away quickly when using a 1/4" drill motor on bearing steel.  Here's a typical kit from Home Depot, you can get an even cheaper type, whatever you care to spend:  81ddd7f5-1449-4065-ae78-850296abf0f2_100 

I suggest that you first trial fit without approaching full torque on the pinion nut.  For trial rough fitting, you're just trying to seat the bearings and fully flatten shims; full torque application is not necessary until you're reasonably close to the right shim stack.  This will work for the YJ Wrangler front Dana 30 since you're relying on shims for both pinion depth and bearing preload (not a crush sleeve for the preload like the Dana 35 rear axle).  

Overall, you have one of two choices:  1) invest in an expensive bearing cap arbor pinion depth kit from Miller/OTC to establish the baseline pinion depth or 2) get yourself plenty of tooth contact marking paste and shims.  If you choose the likely option #2, you'll need to assemble the differential and ring gear/carrier with new ring gear bolts and Loctite 271 on the threads; then after installing the pinion shaft and bearings with trial shims, you can roughly fit the carrier into the axle for trial testing.  This can be done with trial bearings and just enough shimming to take out all lateral play at the carrier bearings; at the same time adjust the gear tooth backlash within factory specification.  

Run a tooth contact pattern test with a slight load on the pinion flange.  I use a shop rag as a "tourniquet" around the flange neck to get a good tooth impression in the marking compound.  Rotate the ring gear with a box-end wrench applied to previously torqued bolts.   

If you trial fit with good used bearings (their bores sanded out to a finger-press fit), you'll be very close to the final fit and preloads.  If anything, there will be only minor shim adjustment at the end.  Keep in mind that the high final pinion nut torque will thoroughly crush the shim stack, and this could change both the pinion depth and the bearing preload.

Note:  As an additional point, I do not trial fit with a new pinion nut.  I save the new pinion nut for what I'm sure will be the last fit-up and torque setting.  You can even grind the outer pinch thread off the old nut for trial fitting.  This will allow quick tightening and removal during the testing.  For final tightening, install the new pinion nut with Loctite on the threads for insurance and additional sealing.

The Dana 35 rear can also be trial fitted.  Use the old crush sleeve for trial testing; you're initially just trying to seat the good used trial fit bearings and flatten the shims enough for an accurate pinion depth reading and approximate bearing preload setting.  Final pinion nut torque is critical at both the Dana 30 and Dana 35 axles; you will need a new crush sleeve at the rear pinion for final preload setting once you're confident you have the correct pinion depth and have installed the new bearings.  Be very careful not to over-tighten the bearing preload on the 35, or you will be installing another new crush sleeve.  If crushed too much, the sleeve must be replace.  You cannot back off the nut and leave a lighter torque setting against the sleeve.  The nut may come loose in service.  Final pinion nut installation requires a new pinion nut with Loctite on the threads.

The tooth contact pattern method is not what you want to hear, but it can ultimately get you the results you want.  Given that you're essentially starting from scratch (there's no magic starting shim stack), the contact pattern will be your only assurance that you've got the pinion depth right.  Pinion bearing preload is the easier part, though many prefer the crush sleeve to a shim stack preload setting.  Trial bearings will make all of this a lot easier.  

If your trial bearings have minimal wear, the new bearings will be a very close match.  You'll be able to press new bearings in place without having to remove them off for additional shim work.  In my experience, quality bearings with close tolerance standards almost always match or interchange.  A good original bearing should be a very close fit to the new bearing, especially for shimming purposes.  Use your intuition here; compensate slightly for any bearing wear.

Moses 

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Thanks, that's kind of what I expected to hear but was hoping there was a "range" on the pre-load stack. At least they did install new Timkens on the pinion when they installed it and I am using new Timkens back so the pinion depth should be pretty easy to get right. The carrier pre-load seems good when I pulled it having to use a small prybar and some enthusiasm.I found a mess in the spider pin where they had use a 1" long roll pin, knocked through so it was only holding on the flange side of the carrier, then they drove another used pin on the button side, bent it over and cut it off, then staked around the hole. I am sure at this point the pinion nut wasn't the only nut involved in this job. I don't have and can't locally source the right roll pin to hold the carrier pin, I'm setting this whole mess aside and just ordered new Tru-Tracs for front and back. If I'm going to have to do a long process trial and set-up, I may as well do it on something strong and useful. Thanks for the help. As the old saying goes, it's hard to find good help these days.

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Mudbullet...I do have a suggestion that might save time...After making your trial bearings for the pinion and carrier, install the pinion without any shims, and tighten the pinion flange nut snugly.  Set the carrier in position without shims and use the bearing caps to hold the bearing cups/races where you want them.  Jockey the ring and pinion gears to simulate the rough gear alignment and backlash; establish a reasonable tooth contact pattern then tighten the bearing caps enough to hold the carrier cups steady—without perceptible carrier lateral movement.  

Use a dial indicator to see how much pinion shaft end play there is between the point that the gears come together with a reasonable tooth contact pattern and the outer position of the pinion shaft when you pull the shaft straight rearward from the axle housing.  This end play measurement will give you a rough shim pack starting point.  Install the rough stack shims and check the pinion shaft end play again while keeping watch on the tooth contact pattern.  Now you can fine tune the shim packs to get the right contact pattern.  Finally, add or subtract the necessary shim thickness for proper bearing preloads, correct pinion depth and backlash.

Note:  All this time, the tooth contact pattern should be governed by Dana/Spicer chart views of proper tooth patterns for the Dana 30.  You'll do the same with the Dana 35 rear axle.  Keep in mind that final torque on the pinion nuts will flatten shims and alter the settings.  Allow for this by tightening the old/test pinion nut securely during your final trial tests...This will help make your new bearing and pinion nut settings match up with the test settings.

We've discussed trial bearings.  These bearings are running in the original races if those races are okay.  You shared that they've only been installed a short time, presumably the races are not damaged.  Once you get your trial fit (pinion depth, carrier centering for the right backlash, and the preload shimming for the bearings of the Dana 30, you can disassemble and change out the races.  Again, there should be only a slight variance between the old cup and cone settings and the new bearing cone and cup/race settings.  Try to estimate that slight difference so that your final assembly will put the bearing preloads, gear backlash and pinion depth exactly where you want it.

Moses 

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I think the pinion depth is going to be a fairly easy job, Motive has the distance etched on the pinion of the inner pinion face to centerline of carrier, 2.038" I believe (don't have it in front of me) as the distance the ring and pinion were match honed to run together. I have a piece of plate that I had parallel ground on both sides and hole through it to use a depth mic. By placing the plate on the bearing cap surface in the housing and checking the distance to the top face of the pinion, then subtracting the plate thickness should get me near dead on the correct shims if I have the pinion in with no shims and snugged down to about 80-100 ft/lbs. It seems it would be at least as accurate as the Ratech tool I see advertised. Do you see any issues with this home brew pinion gage I may be missing? I am assuming the bearing cap surface is parallel to the pinion race seat and perpendicular to the pinion axis. Once I have that set, then setting the carrier for backlash and preload shouldn't be too bad, trial and fit until it's laying a good pattern and the backlash is where it needs to be. It comes back to the shims for the pinon preload that gets me thinking too much. The old bearing races I will be using are dulled but no wear I can detect with a "thumbnail mic", there's no pitting or spalling and they spun quietly on the bench.

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Mudbullet...This bearing cap seam should index with the centerline of the bearing cone/race.  The bearing cap/housing seam should be mid-line of the bearing cup/cone and also the mid-line of the ring gear.  I like your approach.  Let us know how close this turns out.

The Spicer/Dana bare axle housing approach uses discs sized for each bearing cap with a round bar that runs through the disc centers.  The only advantage is that the bar is true centerline for both bearing caps.  If your plate tool bridges between the two bearing cap machined flats in the housing, this would be nearly the same thing.  

Motive Gear has a good approach if they furnish the measurement from the bearing cap/housing seam (the bearing cone centerline) to the pinion head.  See how that works.

Moses 

 

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