Ring & Pinion Pre-Load Shimming

[Toms51]

Hello all.... I am in the middle of my dana 25 rebuild. The gears are all mint and I am just replacing seals, bearings and bearing cups. I’ve seen a million videos on the importance of setting rotational torque. My question- If I duplicate the exact shims that came out and change nothing else, will it not return to the exact location and rotational torque as previously set? If this Jeep, when finished, will only see light duty show/parade use, does this torque thing really matter?
Thank you
Tom

[LarrBeard]

Hello all.... I am in the middle of my dana 25 rebuild. The gears are all mint and I am just replacing seals, bearings and bearing cups. I’ve seen a million videos on the importance of setting rotational torque. My question- If I duplicate the exact shims that came out and change nothing else, will it not return to the exact location and rotational torque as previously set? If this Jeep, when finished, will only see light duty show/parade use, does this torque thing really matter?
Thank you
Tom

BMorgil is the expert on all things Dana/Spicer. He will give you more info that you thought you needed about setting up shim packs and all of the ins and outs or rotational torque.

[bmorgil]

LarryBeard... what a build up!

Tom, setting the correct pinion bearing preload is imperative to the life and durability of a few things. When you are going through the axle your thought process is fairly good. Sticking with the original shim pack thicknesses will always keep things close.

We are looking at the dimensional tolerances between bearing dimensions. You are changing the bearings. They can't be made to the exact same dimensions. You shim it after a rebuild if those tolerances affect the build up. That being said, modern bearings are very, very close. Changes of more than a few thousands of an inch would be unheard of in a quality bearing. If we were going racing I would say proper tools, processes and specifications prevail. Since we are not doing that, You will get great results the way you are going. The shims initially make up for all the manufacturing tolerances. On the pinion depth, if it is not within 2 thousands or so of its original depth, it will begin to get noisy and generate heat. If the ring gear backlash gets too tight or loose, again with the noise and strength becomes an issue. I have set up MANY axles using the original shims and gears with new bearings. The carrier position (backlash) controlled by the shims under the carrier bearings and the pinion position will be just fine reusing or exactly replacing the shims.

So noise is the biggest concern with the position of the gears controlled by the pinion and carrier shims. Way off and it's noisy, runs hotter and is weaker in general. The preload of the bearings is a bit different story. You do need to check and adjust it if needed. The chances are it will be good.

Assemble the carrier into the housing with no pinion in the housing. I am going to assume you don't have a case spreader to drop in the differential assembly. The assembly when shimmed correctly is about a .015" press fit into the housing. This provides the critical carrier bearing preload. Too much and the races may spin out. Too loose and a lot of bad things happen. You should have to VERY carefully slightly cock the races and drive the carrier into the housing. Lube the bearings and use a SOFT dead-blow. This is how outer races get scratched. Do not draw it in with the bearing caps. They will break in half. Drive the carrier all the way in (you will hear it hit home). Torque the caps and pull on the carrier and you should feel a good smooth resistance to rotate. It should take a few foot lbs to rotate it. Incorrect carrier bearing preload is a majior contributor to axle failures.

On to the equally important Pinion bearing preload. Remove the carrier and install the pinion with no seal. Torque the pinion nut to spec (use the old nut). This preload most likely will change. A .001" change in the bearing pack can run the pinion too loose or too tight. Too loose is worse than too tight. The specification to rotate the pinion is 10 to 25 inch lbs. I have no fear running them up to 35 inch lbs. I never run them under 20 inch lbs. If the pinion bearing preload is insufficient, the pinion looses its critical position. The force on a pinion under load is tremendous. It is trying to force the pinion out the front. With no preload everything moves too much.

I hope this helps you! To answer your question in a shorter format, yes it's important!

Bob

I hope this helps you. I have taught a lot of classes on rebuilding the Dana axles. I haven't seen it all but I saw a few. I do know that in every class I ever held, someone would say " I just bang em' in and out and back together with my air gun, I've never had any problems"!

[Toms51]

Thank you very much Bob. That is the most comprehensive answer I’ve gotten on any topic. Between you and the OCD gentlemen in Connecticut that’s rebuilding the engine, I’ve got the same answer. I will use your directions and put this axle together correctly. Is it a regular inch pound torque wrench that is needed? I could use one anyway.
Thanks again
Tom

[LarrBeard]

We're going to start calling you Dr. Dana!

[bmorgil]

Is it a regular inch pound torque wrench that is needed? I could use one anyway

You are welcome Tom!

This is easiest with a good old fashioned "beam style" inch pound wrench.

https://www.amazon.com/dp/B01FMXEWQC?tag=housegrail-20&th=1&psc=1&geniuslink=true

https://www.homedepot.com/p/Presa-1-4-in-Drive-0-in-to-80-in-lbs-Beam-Style-Torque-Wrench-CP31006/206975714?mtc=Shopping-B-F_D25T-G-D25T-25_1_HAND_TOOLS-Multi-NA-Feed-PLA-NA-NA-HandTools_PLA&cm_mmc=Shopping-B-F_D25T-G-D25T-25_1_HAND_TOOLS-Multi-NA-Feed-PLA-NA-NA-HandTools_PLA-71700000034127224-58700003933021546-92700049573927173&gclid=Cj0KCQiAn8nuBRCzARIsAJcdIfPRp7wiEkchudtTQUpJ ratgP4Z8mJMgheikVji0r9nE4M20UL2ncB8aAqXpEALw_wcB&gclsrc=aw.ds

This isn't a real precise measurement. You are going to rotate the pinion with the wrench, floating the handle while trying to read the scale. It will take a torque spike to get it moving. Once you have it rotating you should see it cruising along at a fairly steady reading plus or minus 5 inch pounds or so. An average around 25 inch pounds would be just great! Be sure to use gear lube lightly on the bearings.

[gmwillys]

It is almost a lost art to setting pinions. Dr. Dana has done an excellent job in explaining the process so even I can follow.

[Toms51]

You can say that again! Thanks again Bob, I go into this with a renewed confidence.

[Toms51]

Ok gentlemen, she’s all together, rotational torque set at 20/22 inch pounds. Now on to knuckles and axles. New issue - bought two new spicer type axles from KW. The long one came assembled and the short one came apart (weird) and when I attempt to press the u-joint in I discover that I can just press them in by hand. This does not seem ok even though the guy at kw says it is. I don’t think he knows what he’s talking about. There is no stop or c-clip to prevent the cup from spinning right out to the inside of the knuckle. All u-joints I’ve ever done are a super tight fit that needs a press to install. Any thoughts on this? I tried attaching a short video to show that I can assemble this axle by hand but it says file error. I hope my explanation of this problem is sufficient enough.

[LarrBeard]

Ok gentlemen, she’s all together, rotational torque set at 20/22 inch pounds. Now on to knuckles and axles. New issue - bought two new spicer type axles from KW. The long one came assembled and the short one came apart (weird) and when I attempt to press the u-joint in I discover that I can just press them in by hand. This does not seem ok even though the guy at kw says it is. I don’t think he knows what he’s talking about. There is no stop or c-clip to prevent the cup from spinning right out to the inside of the knuckle. All u-joints I’ve ever done are a super tight fit that needs a press to install. Any thoughts on this? I tried attaching a short video to show that I can assemble this axle by hand but it says file error. I hope my explanation of this problem is sufficient enough.

OK Doc, this one is in your court ...

[bmorgil]

This is a tough one. Only because a high quality part may be hard to find. I had the same issue with my right front axle shaft. First, you are missing the INTERNAL snap rings. The bearing caps are retained by the snap ring on the inside of the yoke ears. See the photo. The U-Joint I purchased from KW was also missing the snap rings. A phone call and I had them the next day.

Now as for the fit. Unfortunately you are correct. A pres fit is the way it was designed. It is a light press fit, as a high interference fit would cause the yoke to distort on assembly. That all being said, Depending on how hard you run the front it may be OK. Not totally correct but OK. I say this because there are a lot of them running around this way. As long as they have some resistance when you push them in. Usually the U-Joint cap gets a little rusty and freezes up in the yoke ear anyway. If you've disassembled one that was "frozen in" you know what I mean!

Here is the failure mode that could occur. Under load the bearing caps could begin to creep extensively. This would wear the yoke ear holes and things will get sloppy. It will make noise and exhibit signs of a worn U-Joint if it ever gets that loose, eventually fracturing the yoke ear. Unless you are running it hard and/or many miles in Four Wheel, I don't think it will ever cause you trouble. If you are going to run it for a lot of miles with the front axles locked in (no hub locks free wheeling) I would shop for a Genuine Spicer Shaft and U-Joints.

I can tell you the shaft I received from KW was incorrectly machined and had to be modified by me before I could even install it. I used it because I was able to make it fit, and Larry needed a ride. The U-Joint fit is less than optimal. There is insufficient press on the bearing caps just like yours. The outside of the yoke had to be machined so it would fit through the hub. The U-Joints they supply are the cheapest I have seen in a long time. I have no idea where this stuff was made. I smell China, India, perhaps the Philippines? They are fine for a parade vehicle that accumulates little miles. They are not for a hard working rig. They are inexpensive however. As I said, I ran it because LarrBeard needed a ride. When the Jeep comes out of storage next year, there are a few little things to fix. The shaft will be replaced with a Genuine Spicer.

For a high quality high strength U-Joint use these https://www.summitracing.com/parts/sdh-5-260x?seid=srese1&gclid=Cj0KCQjwxMmhBhDJARIsANFGOSsPbRluYi-YpkcbwK7GGfNGo0HAmwjUQJlL0DfzuvkK8GDqMCLHjvEaAng_E ALw_wcB

These U-Joints are sealed. No grease zerk. They are designed to seal forever, They work excellent. They are not cross drilled which gives them better strength than a grease-able U-Joint. Remember this is a change in design. The original joint ran in a bath off grease in the closed knuckle. The seals were removed from the U-Joint. This "bath" lubed the pivot bearings as well as the U-Joint. I do not use the "bath" design. I use sealed U-Joints and periodically re-pack the pivot bearings. Filling the knuckle with lube is a messy, leaky old fashioned way of doing it. It does work. Eventually the Knuckles will drip lube on the floor. I like it a bit neater.

[gmwillys]

Bmorgil hit the nail on the head. The caps need the press fit for long life on all parts.

[Toms51]

Well men, I did it. I’m shelving the KW axles and have sourced 2 NOS axles, along with 2 NOS knuckle seals. I really think those are cool, the 2 halves with the paper gasket, hard to find from what I understand.
This leads me to the easy question. Shouldn’t a gasket go between the knuckle and axle spindle. I’m pretty sure there is none based on axle diagrams but that seems weird to me. With all that knuckle lube sloshing around in there, that seems like a good spot for a gasket.

[bmorgil]

No gasket Tom. The lube should not be sloshing around. If it rises that high it will travel past the shaft and into the axle tube. It is important if you are going to fill the knuckles, to use the right lube. Something like this. https://torqueking.com/product/777/closed-knuckle-lubricant-for-closed-knuckle-4x4-front-axles/ . The right lubricant is very thick with a very high viscosity. It is the consistency of room temperature honey. It is similar to what should be in the steering box. A "00" weight so to speak.

This helps with the dripping knuckles. Only eliminating that type of lubrication will cure it completely. If you use sealed U-Joints and re-pack the pivot bearings periodically, filling the knuckle is unnecessary.

[Toms51]

Thank you sir. I have in fact acquired all the lubes for the Jeep, specifically created for vintage Jeeps and sold by the gentleman in Connecticut who is rebuilding my engine. The knuckle lube viscosity is exactly as you describe. I’m going with that way because that’s the way it was and I think it’s cool, messy, but cool.

[gmwillys]

Another option is a product of John Deere, and they use it in their corn heads on combines. It is a 00 grade grease, and it doesn't generally drip when hot.

[bmorgil]

Ya gotta love cool! I admire your perseverance. That original design was the best way they had to insure maximum life from a vehicle that might run in deplorable conditions. Many military personal will attest, they worked in some nasty stuff, above and under the water! As modern tech improved the closed knuckle was left in favor of the sealed stuff.

[Toms51]

Thanks Bob, I would say it’s not so much perseverance as a “why not” attitude. This is strictly a hobby thing for me with no time limit. I’m learning new things, keeping the brain working so I figure why not try to make it the way it was, for the most part. I am building this to putter around, go to a show or 2 and maybe sell it if I get a good offer. It is being built for light duty and any new owner will be firmly told that it is not a rock climber. Building one of those just cost more money that I’d rather spend on my 63 Buick or vacations. Everything in balance, right? Thanks again for your guidance, I’ll be looking for more of it soon.
Stay warm
Tom