Quote:
Originally Posted by Tom Endy
In order to reduce the backlash you need to move the pinion gear closer to the ring gear. The pinion gear is attached to the drive shaft and is located dead center of the car. You cannot move it, but you can move the ring gear. To do this you need to remove the carrier bearings and put a shim under each. This will require the addition of more banjo gaskets in order to re-establish the carrier pre-load. The additional gaskets will give you a latitude to shift the ring gear closer to the pinion gear.
Tom Endy
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Tom,
Moving the pinion gear back also decreases the space between the meshing gears thus reduces backlash. The always dead center pinion gear is cone shaped, smaller at the rear...larger at the front, moving it rearward causes an area of the gear that has a larger circumference to mesh with the ring gear thus reducing clearance between the two rotating parts.
My previously described process of shimming the pinion gear to reduce the backlash is derived directly from information provided by the manufacturer of the gearset. The manufacturer of the gearset stated it was necessary to shim the pinion to get it centered with the ring gear.
(See the description below that explains what "centering the pinion" means.) I followed his instructions and ended up with proper backlash, proper contact pattern and a rear end assembly that dosen't leak, whine or clunk when shifted. Following his instructions worked for me.
Back story: After following your (Tom Endy's) Rear End Assembly Tech Article to the letter, I found I had an unacceptable amount of backlash. I called Steve Becker at Bert's who sold me the 4:11 gear set. He politely offered to replace it with a set of NOS gears. I declined and asked him to provide me the name of the manufacturer. I knew that if I was having a problem, others using this same gear set would too...I wanted to make the manufacturer aware there was a problem with their gear set.
When I called the manufacturer and explained I had set up the assembly with the proper pre-loads and had adjusted the ring gear as close to the pinion as possible and had excessive backlash, the first question he asked me was: "Did you center the pinion gear on the ring gear?"
I said: What?
He then said:
"The pinion gear should have an equal margin of tooth protruding beyond the front and rear of the ring gear when it is properly centered. (He described a centered pinion as the condition where the pinion gear is properly aligned forward to rear (centered) with the ring gear.)
The production manager then politely explained to me the process of centering the pinion to the ring gear (moving it back) by placing shims between the pinion and the tapered bearing closest to the pinion gear.
When I took the assembly apart to inspect the centering, I could see that the pinion gear was too far forward to call it centered. I machined a shim to a thickness that was more than I needed and test fit it. Too tight...Now I had no backlash...I took it apart and machined the shim thinner. I over shot with my machining but corrected my error by adding a .005" Differential Gear Case to Bearing Shim to my machined shim to provide for proper centering and the proper backlash.
Since building up the above described assembly for my touring car, I have built 11 rear end assemblies for customers cars. I have found it beneficial to shim the pinion bearing on only two 2 of the assemblies.
It appears it is not all that common a need to shim the pinion but when it is necessary, because of too much backlash, it is the solution if you cannot shift any more housing gaskets. I no longer machine shims...it is much easier to stack the number of .005" Differential Gear Case to Bearing Shims necessary to achieve proper clearances.
"And now you know the rest of the story... Good Day"