Differential Bearing Preload

[Zimmco]

I came up with a simple tool to rotate the ring gear/differential when setting preload. It's easy to make, very light, and won't hurt the axle seal during all the assembly/disassembly it takes to do this.

Take a piece of approx. 11/16" conduit long enough to reach well past the end of the axle bell and allow an extra 6" or so. Flatten one end to form a loop around a second piece of conduit as long as the differential carrier is wide. Drill and bolt this, allowing some offset so it all centers in the carrier. Wrap tape around the cross piece on the ends so it fits snugly in the carrier. (Don't make the cross piece too long or it'll hit the pinion snout when rotating the assembly). See the photos below to make sense of all this.

I clamped a piece of all-thread to the end sticking out of the axle bell and measured preload with a ruler and a weight. Center the all-thread so it's weight doesn't affect your measurement. You could drill a 1/4" inch hole for the all-thread to pass through conduit rather than clamping it.

 

[ford38v8]

It takes a devious mind to dream up a labor saving device! In my younger days, I'd work out some tool like that to save time or money ...or both, and when all was said and done, I'd worked harder to invent the thing than the job would have taken by doing it by the book! The real payoff on something like this is that it worked and ya beat the system!

On a related note, split the banjo gaskets to allow insertion without removal of the bolts, and use only half the bolts. When the right combination of gaskets has been determined, use a fresh set and bolt it up for good.

Another preload simplifier is for the pinion itself: Put the assembly in a large bench vise, pinion pointed down clamped in the vise. Spin the banjo with both hands as fast and hard as you can. The correct preload will allow no more than one full revolution of the banjo.

 

[Zimmco]

You sound even more devious than me with that split gasket trick! I wish I had thought of that. I did do the pinion spin since I read about it before on here. Being type A, I had to check anyway. It was right on.

 

[hotcoupe]

thanx for sharing that with us,GREAT idea!
tom

 

[JM 35 Sedan]

Al, cool idea! Do you have the pinion gear mounted in the banjo/center housing when you are setting carrier bearing preload?

 

[ford38v8]

john, That's not my original idea, it's one that old time mechanics used. I did mine the old fashioned way with the KRW tool, and wan't confident I'd got it right until this trick was showed me.
To answer your question, the pinion preload is done first, with an otherwise bare banjo.

 

[Zimmco]

John-the pinion wasn't in yet. The torque tube in the photo was just to support the rear hanging off the table so I could rotate it to get to both sides while I did the diff preload. Then the banjo went up on the table without the torque tube or axle housings for the pinion setup. Then I used the whole setup again to check gear lash at the pinion and using my conduit tool just to verify lash at the ring gear. Then I put the seals, axles and spiders in and assembled. Phew!

 

[JM 35 Sedan]

john, That's not my original idea, it's one that old time mechanics used. I did mine the old fashioned way with the KRW tool, and wan't confident I'd got it right until this trick was showed me.
To answer your question, the pinion preload is done first, with an otherwise bare banjo.

Alan, I used that method you had previously posted here (spin banjo with pinion spline in soft jaw vice) back in May when I installed 3.78 gears in my 35 fordor. Worked like a champ. When I set bearing preloaded on carrier/differential housing and ring gear assembly, I did not have the pinion mounted in banjo housing because I did not want that drag to influence my judgement when setting carrier/differential housing preloaded. I also set this preload by placing all gaskets on one side then split that in half on either side of banjo housing prior to setting R&P gear backlash. It all seems to have worked well with no rear gear noise or any other problems with the rear in the last 8k miles.

 

[JM 35 Sedan]

John-the pinion wasn't in yet. The torque tube in the photo was just to support the rear hanging off the table so I could rotate it to get to both sides while I did the diff preload. Then the banjo went up on the table without the torque tube or axle housings for the pinion setup. Then I used the whole setup again to check gear lash at the pinion and using my conduit tool just to verify lash at the ring gear. Then I put the seals, axles and spiders in and assembled. Phew!

Zimmco (Al), we did each step very similarly except I had the assembly mounted vertically for each step. Didn't think of attaching torque tube and using table like you did. Another good idea. I need to rebuild another rear using 3.54 gears for my coupe, so may try your idea's then.