Pinion Bearing Preload
 

I plan on putting in a Mitchell Overdrive unit in my 30 Coupe. I'm on a waiting list to get the unit, so in the meantime I'm stocking up on tools to do the job by myself. Just got a pinion gear puller and installer from Synder's, and when I looked at the instructions I was surprised to see that the puller was also manufactured by Michell Manufacturing. Instructions for the use of the puller said to remove the two large pinion bearing nuts after carefully dimple punching the inner nut to mark its location relative to the keyed slot. Then take off the nuts to install a backing plate. This would destroy the preload for the bearing. Other instructions I have seen regarding the driveline say to remove the pion gear and bearing nuts as a unit so as NOT to destroy the preload. Question is, can the preload be accurately reset by the punched dot method or is it better to remove the unit as an assembly without affecting the preload. Since preload can also be reset using a torque wrench, is it really that sensitive? What's best, keep original preload, use the punch point technique, or use a torque wrench. I'm just a shade tree.

Re: Pinion Bearing Preload
 

The center punch idea would not be repeatable. You are right taking the nuts loose and destroys the preload. You could estimate the prelode

. A tool is available from mitchel to remove as a unit. Then you keep your prelode.
They might rent it orsell it

John

Re: Pinion Bearing Preload
 

Bearings should not be preloaded at room temperature because they need some play for thermal expansion, just like a wheel bearing.

Re: Pinion Bearing Preload
 

One method is to check the preload with an inch pound wrench on the end of the dr. shaft before removing the nuts. Then reset with the same wrench as recommended in publications to 20 inch pounds or hopefully the same value as before removal. There is an article on the Santa Anita A's website for od's.

Re: Pinion Bearing Preload
 

Re: Pinion Bearing Preload
 

I like the idea of trying to determine preload with a torque wrench. It should be about 20. If the existing nut tightens at 16 or 18 for instance, that would tell me the preload was pretty light. The Mitchell pinion and installer kit is only to remove/install pinion from banjo. After that, I will need to pull/drive the pinion from the drive shaft. The Mitchel puller does not work for this...I will need to use a different type of bearing puller. The Mitchell pinion puller uses the large nut as a stop for the plate which contains the three bolts used to tighten against the bajo protector to remove the pinion from the banjo. Messing with this large nut destroys the preload. I am buying some 1 1/8" collars to use as a stop for the puller plate so there will be no need to mess with the preload. This collar that clamps to the driveshaft is described in Tom Endy's "Mitchell Overdrive Installation" article. I don't know why Mitchell's kit doesn't include the driveshaft clamp, but instead uses the preload setting nut as part of the banjo pulling operation.

Re: Pinion Bearing Preload
 

Watch this carefully and then be sure to follow Mitchell’s instructions carefully.
https://m.youtube.com/watch?v=fKRHYlwR7eU

Re: Pinion Bearing Preload
 

You really cant use a torque wrench to check pre load, you need a continuous read type, like an inch pound beam torque wrench. Without going back to my notes, I beleave it is 18 inch pounds.

Re: Pinion Bearing Preload
 

GPierce: Thanks for the video. Very good.

Re: Pinion Bearing Preload
 

My 1935 Motors Manual says you should feel a light drag on used bearings and a heavy drag on new bearings. I would not remove the nuts, but if no drag is felt, I would tighten them just enough to get a slight drag. Keep in mind the outer nut will change the drag when it is tightened. these rear ends do not require a rocket scientist to work on them.

Re: Pinion Bearing Preload
 

Jim , I could not agree with you more that it doesn’t take a “rocket scientist”. While I am a hot rod Chevy guy who loves my 28 model A more than all my cars and am/ have been , learning the quirks and specialties of working on my car every day for years I can’t help but think after reading a ton of posts about everything on the A forums that there is a lot of over thinking about stuff… granted some things are more specific to some things on an A than other cars the basic principles to me are very similar to vehicles in general. When I put my Mitchell in I set it up by feel and it has been working perfectly for 5 years and about 10,000 miles. Am I wrong in this assumption? And yes, I do know what happens when you assume��

Re: Pinion Bearing Preload
 

Marc, ya done good!

Re: Pinion Bearing Preload
 

You could send your puller back. The Mitchell comes with one. I would also just do it according to the instructions how ever on reassembly I would just reset the preload. It's not that hard and only adds a little time to the project.

Re: Pinion Bearing Preload
 

The pros that do modern rear ends even to this day, do it by feel. They do not waist time checking rolling torque with beam or dial type wrench.
As has been said and repeated; It's not rocket science.

Re: Pinion Bearing Preload
 

This is incorrect. These are not wheel bearings. They need to hold the gears perfectly with no play. Keep in mind that thermal expansion also cause the housing and shaft to grow and lenghten.

Re: Pinion Bearing Preload
 

One thing that is not mentioned is what was the preload before disassembly? I have seen some that had almost zero preload.
The 20 inch pounds recommended is for new bearings, that will wear in. I shoot for about 5 inch pounds with used bearings, as they are worn in to each other. This is easily checked with a beam style torque wrench, but the shaft needs to be vertical to be accurate.
Contrary to posts above, the puller does not come with the OD Unit.

Re: Pinion Bearing Preload
 

There is an excellent article about rebuilding a rear axle in the Jan-Feb 1995 Restorer magazine "Model A Ford Rear Axle Adjustment", starting on Page 10. I highly recommend reading this article. I used this method on my car and it worked well.

Re: Pinion Bearing Preload
 

You are correct. Thank you for catching my error. The unit DOES NOT come with a pinion puller.

Re: Pinion Bearing Preload
 

go to santaanitaas.org it has the best pictures and instructions on the scroll down to preload on the pinion. Bearings are precision don't take a chance with someone telling you to just guess at it these old cars were built to higher standards than most think thats why so many are still running on the roads. the old punch mark is a hit and most times mis as you are setting by sight not torque. going to the trouble you are it just takes a little more time to do it right. as for taking it out as a unit I can't see it being done as the pnion has to have one timken bearing install and slide from inside housing and the the outboard bearing is put on and it can't go through to the inside of the housing. thats when you torque them together.
So don't try it or you will bust the ring out of the housing that holds all together. Just my two cents for what it's worth it I've seen and heard so much mis information on this I had to reply
Jim
IHS