Move Pinion forward and back per Les Andrews

[Al 29Tudor]

Hi Gents,
We are in the middle of dis-assembling a 1928 differential.
In Les Andrews red book, page 1-95 picture in lower right hand corner he shows two gear teeth with wear patterns and text says, "move pinion forward" and "move pinion back"
I don't think there is any adjustment for pinion other than Preload.
Am I missing something.
Thanks for your help.
Al Leach, Venice, FL

[Tom Endy]

The only way you can move the pinion forward or back is to either take a cut on the bearing stop on the pinion or add shims. I don't believe any of this is necessary. I have never found shims on a pinion and I have had a great many apart.

Once the pre-load is set on the carrier and pinion bearings a backlash adjustment is made by shifting the banjo gasket Left\right. This moves the ring gear either closer or farther away from the pinion. The pinion is straight down the center line of the car and you cannot shift it left\right.

Suggestion:

Got to the web site of the Santa Anita A's of Arcadia, California at www.santaanitaas.org . Put your cursor on "Technical Reference" , my name will drop down below. Click on it and it will bring up a menu of technical articles. Scroll to the three on differentials. You can download them. This may be of help.

Tom Endy

[Dave in MN]

[QUOTE=Tom Endy;1348631]The only way you can move the pinion forward or back is to either take a cut on the bearing stop on the pinion or add shims. I don't believe any of this is necessary. I have never found shims on a pinion and I have had a great many apart.

Once the pre-load is set on the carrier and pinion bearings a backlash adjustment is made by shifting the banjo gasket left\right. This moves the ring gear either closer or farther away from the pinion. The pinion is straight down the center line of the car and you cannot shift it left\right.


Tom,
Please consider the following:

I agree with you in that I also see no need to ever make a cut on the bearing stop of the pinion gear. I, like you, have never seen one too tight or with too little backlash.

I disagree with you that it is never necessary to shim the pinion. As you can see from the photo in my original post (#14), when studying the contact pattern with white lithium grease, the contact pattern was not even close to satisfactory. This condition was caused by excessive clearance between the pinion gear and the ring gear and that equates to excessive backlash. This photo was taken with all but one gasket moved to the other side in an effort to lessen the backlash.
I agree that it is obvious that the centerline of the pinion gear can not be changed from left to right by adding shims to the pinion but since the pinion gear has a basic cone shape, moving it towards the rear, with a shim, will decrease the clearance between the pinion and the ring gear. Just as important, moving the pinion back may better center the contact pattern of the gears.

When I was rebuilding the rear end assembly for my touring car, I contacted the manufacturer of the gearset because just shifting gaskets was far from what was needed to obtain a good contact pattern and backlash. The first thing he asked me was, "Did you visually center the pinion gear on the ring gear?" He also said: "The only way to obtain proper meshing is to complete this step and that will require shimming the pinion gear." Now remember, he was specifically talking about the gearset he manufactured. After installing and adjusting the thickness of the shim at the pinion, everything came together almost perfectly. Now remember, this gearset is a 4:11 and is likely a ratio not many people purchase new and install. The other ratio gearsets may be manufactured differently and may not require shimming to obtain an acceptable backlash.

I know you consider the backlash adjustment "the least critical of all the adjustments" and in your restoration guidelines state that: "Generally you may end up with more backlash than you want. This is usually due to the wear in a used ring & pinion gearset, and it cannot be avoided." I'm just proposing that it is possible to obtain a very good tooth contact pattern with no excessive backlash if the extra step is taken to shim the pinion when warranted. IMO: A worn/used gearset may warrant shimming the pinion.

Installing and adjusting the thickness of the shims between the pinion gear bearing stop and the pressed on taper bearing takes extra assembly time. I pressed the rear bearing on and off several times, each time adjusting the thickness of the shim, to obtain the proper mesh and backlash. It is not hard and like the rest of the rebuilding process just tedious.

By the way Tom, Thank you for your very detailed and well written Model A Ford Rear Axle Assembly Restoration (2014 Revision) Technical guideline. I used it as a manual for the differential clinics I hosted this past winter. I printed it in whole for each attendee to refer to during the clinic and to take with them.
Good Day!

[Al 29Tudor]

Thank you Tom.
Sent you a PM earlier.
Yes, I didn't see any provision for adjustment of the pinion other than pre-load.
Your tutorial from earlier this year on the 1928 differential has been really an excellent guide for our project.
I'm setting up a step by step list of everything to do with a check box so we don't miss anything.
Thank you again.
Al Leach

[Tom Endy]

Originally Posted by Al 29Tudor

Thank you Tom.
Sent you a PM earlier.
Yes, I didn't see any provision for adjustment of the pinion other than pre-load.
Your tutorial from earlier this year on the 1928 differential has been really an excellent guide for our project.
I'm setting up a step by step list of everything to do with a check box so we don't miss anything.
Thank you again.
Al Leach

You need the 2014 tutorial, it is pretty much a check list.

Tom Endy

[Al 29Tudor]

Sponsored Links (Register now to hide all advertisements)

OK Tom, I'll get it
Thanks again.
Al

[BILL WILLIAMSON]

Remember, as to the ring gear tooth contact area, you try to get a PEANUT shaped area, CENTERED on the ring gear TOOTH!
Bill W.

[Al 29Tudor]

Thank you Bill.
We will try to get that pattern.
Tomorrow we will install another members engine and then get back to the rear-end project full time. (well full time ???)
Al

[Jim Brierley]

Both articles by Tom and Les are very good. I do have a disagreement with Les when his book says to bolt both axle housing halves together to get a preliminary pre-load check. (or words to that effect). Bolting the halves together without shims (gaskets) can bend the housings and result in leaks. I recommend bolting the left housing on,(I use only 4 bolts at this ( time) place the assembly on end and slip the right side on. Now measure the gap between the housing and the center section. This will tell you how many gaskets to use. Now install half that thickness on both sides and check backlash. This is time consuming but worth the effort. Just my opinion!

[Tom Endy]

Originally Posted by Jim Brierley

Both articles by Tom and Les are very good. I do have a disagreement with Les when his book says to bolt both axle housing halves together to get a preliminary pre-load check. (or words to that effect). Bolting the halves together without shims (gaskets) can bend the housings and result in leaks. I recommend bolting the left housing on,(I use only 4 bolts at this ( time) place the assembly on end and slip the right side on. Now measure the gap between the housing and the center section. This will tell you how many gaskets to use. Now install half that thickness on both sides and check backlash. This is time consuming but worth the effort. Just my opinion!

My technique is to bolt the right axle housing to the right side of the banjo with no gaskets and torque the bolts down to 35 ft. lbs. With the carrier assembly installed I add two .010 gaskets to the left side of the banjo and attached the left axle housing and begin pulling all the bolts down toward 35 ft. lbs. stopping periodically to check that I can turn the ring gear with my finger by reaching in through the torque tube flange on the banjo. If I feel it getting too tight I stop and add one or more gaskets. In this manner no strain is put on any of the hardware.

Two .010 gaskets is the least amount of gaskets I want to end up with. Anything less and there is liable to be an oil leak.

Tom Endy

[larrys40]

Originally Posted by Tom Endy

My technique is to bolt the right axle housing to the right side of the banjo with no gaskets and torque the bolts down to 35 ft. lbs. With the carrier assembly installed I add two .010 gaskets to the left side of the banjo and attached the left axle housing and begin pulling all the bolts down toward 35 ft. lbs. stopping periodically to check that I can turn the ring gear with my finger by reaching in through the torque tube flange on the banjo. If I feel it getting too tight I stop and add one or more gaskets. In this manner no strain is put on any of the hardware.

Two .010 gaskets is the least amount of gaskets I want to end up with. Anything less and there is liable to be an oil leak.

Tom Endy

Al,
Like Tom I have done many rear axles... our only difference is I go ahead and split the .020 thickness and mount a .010 gasket on each side as a starting point.And adjust add subtract, change left to right as needed for proper gear contact and preload. dab 4 small points of rtv at equal places to hold the gaskets and then see where things fall. A agree with Tom that I have never had to shim or adjust the Pinion bearing/race by shimming it. Your tooth contact is dictated fine by the preload and shim of the carrier bearings by the various gasket thicknesses.

Once correct gasket thickness is determined seal well with a skim of rtv including a little on the threads ( especially lower half) of carrier bolts to ensure that there is no leakage there.

Good luck!
Larry Shepard

[Growley bear]

Originally Posted by Jim Brierley

Both articles by Tom and Les are very good. I do have a disagreement with Les when his book says to bolt both axle housing halves together to get a preliminary pre-load check. (or words to that effect). Bolting the halves together without shims (gaskets) can bend the housings and result in leaks. I recommend bolting the left housing on,(I use only 4 bolts at this ( time) place the assembly on end and slip the right side on. Now measure the gap between the housing and the center section. This will tell you how many gaskets to use. Now install half that thickness on both sides and check backlash. This is time consuming but worth the effort. Just my opinion!

Yes, and that process can ruin cups and cones if squeezed too hard. They end up looking like a pinion bearing that had the preload set with a rattle wrench.

[Jim Mason]

Seems to me the depth of the pocket for the pinion double cup was changed at the same time the gusset was added. either on vince's or marco's site for the drawing...

[Al 29Tudor]

Jim,
I think Les starts with an equal number of shims on each side and reduces from there.
Your comment explains why - so the housings are not distorted.
Thanks.
Al

[Al 29Tudor]

I'm putting this out there to see if I understand the procedures.

1. Carrier pre-load. Assemble and install carrier, no spider or axles, bolt up both axle housings. Add spacers under carrier bearing races in axle housings until carrier won't turn. (Is it ever necessary to shim the races?)

2. Bolt up banjo and right axle housing and set in carrier. Add minimum of two .010 gaskets, then bolt up left axle housing, maybe more gaskets, until carrier turns snugly, making sure I never bind up or distort the axle housings.

3. Now divide the gaskets 1/2 on each side and proceed to pinion and ring gear pattern and backlash. Always keeping the same gasket stack and locating the gaskets to either side as required to achieve proper wear pattern and backlash.

Please correct me or confirm I got it right.
Thank you Tom and Jim for your time and patience.
Al

[Al 29Tudor]

Tom,
[1. Carrier pre-load. Assemble and install carrier, no spider or axles, bolt up both axle housings. Add spacers under carrier bearing races in axle housings until carrier won't turn. (Is it ever necessary to shim the races?)]
Page 34 of your 2014 dissertation answers this question and states any shims required can go under the bearing - easier than the race in the axle housing.
Next get a handle on the yoke.
Wow!
Al Leach

[Dave in MN]

Sorry, I have not read Les Andrews section in his book about shimming the pinion. I am offering the following from a recent experience regarding the ill fit of a new 4:11 gearset.

Last year, early in the driving season, I lost a tooth on my 4:11 gearset when the double nuts on the pinion gear loosened. I ordered a replacement 4:11 set and installed it using Tom Endy's very detailed write-up. Upon completion and with the maximum number of gaskets shifted to lessen the backlash between the pinion gear and the ring gear, I still had an excessive amount of backlash in the neighborhood of .070".

Not being satisfied with this amount, I contacted Steve Becker at Bert's who gave me the name and contact info of the manufacturer of the gearset. The manufacturer coached me on the procedure of centering the pinion gear to the ring gear prior to starting the assembly procedure. I determined I needed and then machined a shim that was .067" to place between the pinion gear and the first tapered bearing. With this shim in place and again using Tom Endy's procedure, I was able to obtain about .005" backlash with adequate but not excessive gaskets to provide a good seal to the components. The assembled rear end is very quiet and took us to Loveland and back this summer.

Because of the difficulty I had with acheiving proper backlash in my own rearend assembly, I decided to put on a differential rebuilding clinic at my workshop. There were about 20 local club members in attendance for each session. I held one session where we took two assemblies apart and evaluated their condition and developed a list of repairs to complete and components to purchase for restoration. After the components were repaired and new parts purchased, I hosted two additional Saturday sessions where we assembled the differentials. One assembly needed shims at the pinion gear to get the backlash exactly where we wanted it. The other assembly did not require any shims.

It is often said or assumed you can only get the backlash as good as the shifting of gaskets will allow. This statement is true if you don't try adding shims between the pinion gear and the first or rear tapered bearing you press on to the pinion. The bearing shims sold in .005" thickness for shimming the carrier races can be used between the pinion gear and the rear bearing that is pressed on to the pinion. They fit the components perfectly. During the clinic I hosted, we did use 7 of these shims to obtain the proper pinion gear centering on one differential.

An interesting side to all of this was that when the pinion was properly centered and the backlash was correct, we had a good contact pattern when checking the assembled components with yellow bearing grease laced with yellow pigment.

The first photo (white lithium grease) shows the contact pattern before shimming the pinion gear. It has a bad pattern with the pinion gear teeth riding over the edge or crest of the ring gear teeth. This state would not last long. This contact pattern was the best I could achieve by just shifting gaskets at the pumpkin. Excessive backlash was very evident in this case. This was a new 4:11 gearset.

The next two photos show a more centered engagement on both the thrust and coast side of the 4:11 ring gear. This pattern was achieved with shims (.067") at the pinion as described above. The backlash was about .005".

Good Day!

[Jim Mason]

Bad memory it was the axel housing that was changed

http://www.abarnyard.com/workshop/rearend.htm

[Al 29Tudor]

Thank you Dave,
That's great information and I have filed it for our project.
Our banjo is cracked at four tube mounting holes/bosses so a new banjo may require shimming.
Thank you again,
Al Leach

[Ed Saniewski]

Dave, any chance someone recorded the work session and could post it on youtube? A class like that would be wonderful to share with us. Thanks, Ed Saniewski