Dana 30 Pinion Preload Shim Stack

[Mudbullet]

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!

[Moses Ludel]

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:   

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 

[Mudbullet]

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.

[Moses Ludel]

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 

[Mudbullet]

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.

[Moses Ludel]

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 

 

[Mudbullet]

I haven't had a chance to do anything this week, I'm starting back on it this weekend. I will take some pics of my tool and how I am using it. Maybe it will help some others to make a faster setup. It could also be used to check the pinion depth before removing an old pinion to get a reference to setting a new gear back up. Thanks for all the help, I'll keep posting with progress.

[Moses Ludel]

Mudbullet...I really like your suggestion about checking the OE pinion's depth before removing it!  Assuming the gear and axle housing are original and accurate, with bearings reasonably fit, you would have a great reference/starting point for shims.  Good idea...

Your approach with the reference measuring plate is sensible and quickly demystifies the pinion depth set-up if we reuse the same axle housing.  Installers need to understand that the pinion depth shim stack varies between pinion gears and also between axle housings or drop-in third members.  

Using your preliminary depth reading, you can take the pinion head marks from the old pinion and new pinion.  If the new pinion offers the Dana +/- marks offered in a mark chart, you can determine the shim thickness difference between the two gears.  Adding or subtracting the right shim thickness should place the new pinion head at the right depth.  Without +/- marks, matching the pinion depth measurements in the housing will serve the same purpose.

Looking forward to your photos...Thanks!

Moses

[Mudbullet]

Another helpful thing I figured out by accident as I was standing in front of my drill press sanding out my test bearings (takes a while) and I could tell my drill press was getting tired of the side loading on its bearings. I considered a spindle sander but those things are pricey even for a cheap one. I am using my table saw top for a clean surface and because it has a ground cast iron surface so it is flatter than my work bench, I stopped sanding to test fit my bearing and the light went off, the other side of the table on my saw is set up for a router. I slid the fence back, put my sanding drum in my router, slowed the spindle speed down a tad, then made quick and more accurate work of it. The bearing can sit on the flat surface and then just work it around the drum sander. Cheap router tables can be found used or even Harbor Freight routers will work. The bearings in a router are designed for side loads so you won't be doing any damage like with a drill or drill press and you end up with a better more accurate test bearing than by trying to hold it flat on the drum with no support under it in a drill press or using a hand drill.

Another thing I found on the Motive brand gear set, in addition to the depth from carrier centerline to the top of the pinion gear, they also mark the backlash on the ring gear the set was hone meshed to. On my Dana 30, it was set at 2.261" pinion depth and .006" backlash, that's a very accurate bullseye to aim for and I'm thankful that information was included in the set.

[Moses Ludel]

Two huge time-savers...The router and deck idea is very smart, I've done many bearings with sand drums and had to back off constantly to avoid side loading my drill press.  Also, control is so much better with your flat deck and router approach!  This helps maintain a precise bearing bore.

Motive's backlash marking plus providing the pinion depth measurement is brilliant.  If you do this carefully, the setup should be right on, a huge time saver.  Then there are only the bearing preloads to consider.

I came into the automotive/truck mechanical trade at a time when Dana/Spicer and others outlined archaic methods for setting up gears and preloads.  In updated form, these tools are still provided to dealerships and appear in contemporary factory shop manuals.

Note:  I have a 6' tall bookcase of FSMs from the 1920s to 2007 that show complex and often expensive tools for axle gear change-outs.  Carrier centerline-to-pinion head measuring fixtures date to the 1910s and earliest hypoid gear sets.  I have Dana 25 through Dana 80 Miller axle centerline indexing tools that are way more complex than your plate method; these dealership-level tools take longer to use and achieve essentially the same results as your approach...If the axle housing is true with the pinion shaft centerline precisely perpendicular to the carrier bearings' centerline, you can even install gears in a new, raw axle using your method—and Motive's measurements.  It has been argued for years that arbor disks, a centering bar and a special pinion block holder for the dial indicator is the only reliable method...not necessarily!

Aftermarket tools like bearing cone simulators were the first move away from expensive centerline alignment tools.  My bearing bore sanding method is basically a knock-off of the bearing cone tools.  If you're not doing these axles day in and out, a set of sanded used bearings will suffice.  I have a number of mock used axle bearing sets in my gear work tool box.  Label your handiwork for the Dana 30 and Dana 35 axles.

Motive has taken the setup method to the next level by focusing on the fundamental goal of gear matching:  pinion depth, ring gear alignment and gear backlash.  Bearing preload settings are the follow-through steps.  Looking forward to your photos...

Moses

[Mudbullet]

Well, I've had a crash course in differentials (almost literally) the past couple weeks, My Astro van dropped a c-clip and the right axle parted company with the housing. It appears the hardening wasn't deep enough on the tip end of the axle, actually both axles. They have sort of a reverse mushroom head on them now, the outer edge sharp and hard, the center of the axles were badly cupped like a worn out cam lifter. The outer edge had finally worn into the pin enough to let the axle slide in and drop the c-clip. Luckily I was able to get it off the road and stopped before the axle was completely out of the housing but I've been pretty busy putting everything back together.

I will post what I've done so far on the Jeep though. Here's the pinion head etched with the depth. The second picture is the router in action. It is a variable speed and I ran it at about half, I wouldn't want to run it much quicker. The sparks show just how effective it was. The sandpaper rolls worked so much better. I had already went through three 80 grit 3/4" rolls on one carrier bearing and about half done on the second. The third picture shows the 3/4" 80 grit roll from the router which finished the second carrier bearing and did both pinion bearings. It was still cutting well too. I swapped to a 1" roll to do the races because of the increased diameter of them.

The fourth picture is the basic concoction I came up with, I hadn't drilled the hole yet but it is a piece of cold rolled that started at 1/4" nominal, ground flat then parallel, 2" wide by 6" long.

The first thing I did was measure my plate thickness in several places to make sure it was consistent then zeroed the calipers, that way all measurements will be taken minus the plate thickness.

I located and drilled the hole and deburred, then put my pinion in with only the oil slinger and test bearings, torqued it to about 65 ft.lbs. and checked the pinion head depth (7th pic) it came out to 2.2835" with a target of 2.261" I was 0.0225" too shallow. My shim assortment wasn't tremendous but I chose the two I measured at 0.0115", re-torqued the pinion at the same value as before and I got 2.258", 0.003" deep but I feel certain that will decrease at full torque.

I've pressed the new bearing on and have everything ready to start assembly, hopefully some time this week.

 

[Mudbullet]

I also put my ring gear on, I snugged 4 bolts up pretty tight then set my indicator up and spun the carrier slowly to make sure there was no strange run-out. I then put the bolts in and torqued in two stages to spec with red Loctite, hence the silver hash marks (silver Sharpies rule!). I then re-checked the run-out and it was dead on.

As for the gear set-up, like you stated above, it has always been presented as almost an alchemy science. That's one reason I have never attempted a gear change but thanks to YouTube "University" and your article, I finally understood the set-up and what was critical and what was secondary. From the world I am used to working in, the pinion tolerance of +/-.002 is a huge ballpark to play in. I came from an industry that made dental drills and files for root canals where the tolerance is 3 place metric. My calipers are accurate to */-.001 so I should be good.

I hope my gear change will encourage others to do their own, nothing quite as rewarding for an old wrench spinner than to learn something new and do it successfully.

[Moses Ludel]

Mudbullet...I am so pleased that you've shared your learning curve and confident approach.  Others will benefit greatly...The router for the sanding drums is such a time saver!  Much more accurate as well, the drum is a true 90-degrees from the bearing cups and inner race collars.  I like your flat 1/4" thick plate, too...easy to do the math.  Nice!

Excited to see how close your tooth contact pattern turns out after using Motion Gear's pinion head depth measurement.  The 0.003" might be a consideration, you'll have to see.  In any case, if Motion is accurate you have the actual gear lapping index.  The proof will be in the tooth contact pattern on Drive and Coast sides.  

Don't forget to load the pinion shaft (the tourniquet rag on the pinion flange works) while making a tooth impression in the marking paint.

Thanks for taking the time to share photos!

Moses

[Mudbullet]

I'll certainly re-check the pinion depth when I set the preload (hopefully today) while the pinion is at full torque. If it's still deep, I'll order a shim assortment. I probably need to do that anyway since the 4:56 gears I am taking out will go back in my son's Cherokee and my daughter's Grand Cherokee has the typical rear whine going on so I need to rebuild it. I may even invest in a case spreader, certainly seems like a much better way to get the carrier in and out especially on the carriers which have the shims on the outside, much less likelihood of damaging a shim getting everything in place. Thanks for the encouragement, I'll keep posting until the job is done and test driven.

Something Motive has in their instructions I haven't seen in any others (haven't looked at a whole bunch of others) or in any install tutorials, heat soaking and cool down on initial driving. As part of their warranty, you must drive the vehicle 10 miles then allow the differentials to completely cool down, this is to be done 3 times. I assume it is to prevent overheating and possibly annealing the hardening of the gear contact surfaces. Probably isn't a bad idea regardless of who's gear set a person uses. I could see this causing catastrophic wear very quickly if the gears should happen to soften and I wonder if it may be the source of some failures where the set-up was suspected when in fact, the set-up was fine, the gears just weren't broken in correctly. I think most people never realize just how much heat is generated in a differential. I can attest to the fact they can generate 2nd degree burns if you happen to get in contact with the housing after a long drive. Anyway, I thought I would add that info.

[Moses Ludel]

Yes, new axle builds have a lot of initial heat...Motive is not over-reacting, they have to warrant these gear kits.  Most don't realize that new axles require break-in, there is little discussion about new cars and trucks needing to break-in their axles.  

I never tow with a new axle build until the break-in/cycling is well over.  I also like to change the lube at 500 miles or so.  A less expensive synthetic oil can be used for the first fill.  There is always some oil contamination from an axle break-in.