Ring/Pinion Backlash

[Phred]

I'm setting up a Model A differential.

According to Les Andrews book, .008 - .010 backlash is required at pinion - ring gear.

1) according to the photo attached, I am measuring with a dial indicator at the small end of the pinion, tangent to the tooth. Is my setup an accurate way to measure the backlash?

2) I get a reading of .007". While this nearly falls into the range listed in Andrews' book, when turning the driveshaft by hand (gears are dry, no oil or grease) it "feels" like a lot of play. Does the thick 600W gear oil take up the slack?

Thanks in advance Fordbarn.

[Tom Wesenberg]

That should work fine and give room for the gear oil to do it's job.
I like to use blueing to check the wear pattern.

[Ed Saniewski]

Phred, take a look at Tom Endy's instructions on rebuilding rears. I printed them out and use them over and over again. http://www.santaanitaas.org/technica...tech-articles/ .

[harleytoprock]

How can the measurement be accurate with no axle housings torqued down?

[Phred]

There is no access to the gears in this quick change housing when both axle tubes are in place. the differential carrier is resting in the LH bearing cup/axle tube. Gravity and hand pressure kept it firmly in the bearing cup during measurements, and measurements were consistent.

When rotating the pinion drive shaft by hand, the "feel" of the amount of backlash was the same with the RH axle tube on or off. I would suspect my readings are pretty darn close.

Any additional suggestions on how to get a reading in this case would be appreciated.

[Ron in Quincy]

Sponsored Links (Register now to hide all advertisements)

The only other item you might want to check is on page 382 of the Service Bulletins, October 1929, it covers the axel housing gaskets to use depending on your axel housings; the carrier bearings were moved inward a few thousands to reduce end play ; this is when the .010 housings gaskets came into being; the article says to use, as I recall, .006 housings gaskets in the earlier housings to reduce end play.
Note: if you look at the S.B. index it shows (truck) which is a misprint and the article is actually for passenger car rear ends.
I could be wrong but I think some people, when rebuilding a rear end, may not have matching axel housings and run into the problem of one side end play is different than the other ? this condition could certainly contribute to excess back lash.

Ron Rude

[jetmek]

NO install and torque side housings ck backlash at pinion shaft /...006 is desired backlash

[jetmek]

if its a QC, check at output to change gear splined end of pinion

[harleytoprock]

Your in the wrong direction. First you need to set the rotational drag pre-load on the carrier bearings. That's done with torqued axle housings on and by adjusting number of gaskets. Then you ready to adjust gear back lash with torqued housings on and same gaskets. Adjusting back lash is by moving gaskets from one side to the other. Total number of gaskets must be the same as when carrier pre-load was set. It's all time consuming.

[Phred]

Carrier and pinion preloads are set fine. I understand the concept of changing the shims from side to side to adjust backlash.

As shown in post #1, I was curious if my measuring at the small end of the pinion gear was reliable/accurate place to measure backlash.

Jetmek: Measuring at the spur gear end of the pinion driveshaft is a great idea, thank you. Everything can be installed, tightened, and measured easily that way. I suspect results should be similar to my original measurements.

Thanks again.

[tbirdtbird]

The biggest favor you can do yourself right now is as another posted said:
Ignore Les Andrews and immediately go to Tom Endy's web pages for the DEFINITIVE way to do things.
Link is above

[Ron in Quincy]

I have rebuilt at least 10 rear ends, 28 t0 31 over the years. The most important part is the pre-lode on the pinion, knowing you have matched axel housings, good spider gears and housings, use the gaskets as directed in the service bulletins which I reference in my previous post; According to a Ford mechanic, who was a good friend of mine and retired from a Ford dealership in Sacramento quote" the only thing we made sure of when working on the A's and early V8 rear ends, that the pre load on the pinion was correct, we did not worry about back lash, we used a single gasket on each side of the axel housings"
That is how I have rebuilt the rear ends for my As and have never had any problems. I personally do not feel it is necessary to go through what some restorers go through when rebuilding a rear end, and it scares some new A owners so they are afraid to tackle the job.

Just my opinion,

Ron

[Mitch//pa]

Originally Posted by Ron in Quincy

I have rebuilt at least 10 rear ends, 28 t0 31 over the years. The most important part is the pre-lode on the pinion, knowing you have matched axel housings, good spider gears and housings, use the gaskets as directed in the service bulletins which I reference in my previous post; According to a Ford mechanic, who was a good friend of mine and retired from a Ford dealership in Sacramento quote" the only thing we made sure of when working on the A's and early V8 rear ends, that the pre load on the pinion was correct, we did not worry about back lash, we used a single gasket on each side of the axel housings"
That is how I have rebuilt the rear ends for my As and have never had any problems. I personally do not feel it is necessary to go through what some restorers go through when rebuilding a rear end, and it scares some new A owners so they are afraid to tackle the job.

Just my opinion,

Ron

I have no doubt this method was used by many many and I am wondering if that's why we see so many spun carrier bearings..

[john in illinois]

I have done several banjo rear ends. On the last one -a v8-I learned something interesting about preload. I was getting some help from a guy who rebuilds and manufactures quick change and other banjo rear ends exclusively.. He told me that if you set pinion preload and assemble the bells,the torque to turn the pinion shaft is the sum of pinion torque plus the carrier. Thus for example if pinion is 10 in lb and total is 18 then carrier is 8. This can save time as you do not have to measure carrier pre load separately. Tom Endy's tutorial is very valuable for all v8 and A rear ends.