I'm putting a 12 tooth pinion in one of my Ruckstells. I've tried a search, as I think it's been discussed before, but cannot find what clearance I should aim for. I suspect I should be looser than with the stock 11 tooth, but don't know how much.
I looked in my Ruckstell book and it suggests a clearance of .008-.012. that is with stock 13/39 gears. I've got .010 with 2 paper shims in place between the differential housing and the drive shaft. Is that enough or should I add another? My stock 39 tooth ring "shouldn't" work but I had to have my bronze thrust plate machined flat and that added the clearance to get me close.
Noel, I don't know about the Ruxtell, But Glenn Chaffin suggests .005 to .006 if there is no run-out. .010 should be acceptable if there is .003-.004 run-out. (pg 28 of his guide).
Noel,
The stock pinion/ring is 11/40. The 13/39 is the 3:1 high seed ratio set.
I put a 3:1 in mine and had about 0.006". It runs free with no abnormal noise.
From:
http://www.mtfca.com/discus/messages/179374/247500.html?1321737832
Glen Chaffin said, "Every rearend is different. Don't judge clearance by shim thickness. Actually measure it with a dial indicator. Hold the pinion gear stationary and rock the ring gear from side to side and measure the total travel with the dial indicator. You want no less than 0.005 and no more than 0.010.
Sounds good to me.
Jim
i measured my clearance with feeler gauges, Rocking the ring gear back and forth seeing if the feeler gauge would fall or pick up the tooth on the gear. Not saying it is the right way because it is a pain but no dial indicator was available.
Thanks, guys. I guess I'll be safe with the .010. I tried using solder to see my clearance but only ended up with broken chunks of flattened solder. Using my dial indicator like Jim mentioned gives me the .010. With only one shim in, and around .005, the gears still felt like they were bottoming out and hitting as I rotated them. The teeth on the new 12 tooth pinion are a bit more rounded than on the stock 13 tooth pinion, and I thought I'd read somewhere that they needed more clearance. Jim, there is a 12 tooth pinion made to be halfway between stock and the 3:1 set-up. I'm hoping for a little less RPM at cruising speed and think I have a good engine to pull it, along with the underdrive of the Ruckstell for pulling hills.
I like Jack Daron's suggestion for pinion backlash: "If it will bend (crimp) and not cut a piece of copy paper,it is good."
http://www.mtfca.com/discus/messages/257047/283426.html?1334937205
Les Schubert's suggestion from another thread is similar:
"A good test is run a strip of good "bond" writing paper through the gears. If all the clearance is removed when the paper is in between the gears then you are probably in good shape. Yes you will have to have the right side housing off to do this, with the drive shaft bolted up to the left side housing."
http://www.mtfca.com/discus/messages/257047/262113.html?1327720351
Aaron Griffey warns in a third thread about the dangers of getting it too tight: "I would rather have the clearance a bit looser, like .014 in the tightest spot.
Up to .020 is just fine. .010 might be okay for slower speeds but if you are gonna push it close to 50MPH you'd better stay on the loose side or it could start slinging teeth."
http://www.mtfca.com/discus/messages/118802/130519.html?1268753631
If you have the gears properly meshed, meaning running smoothly with each other and with a full contact area, the clearance will take care of itself. Too much emphasis is put on clearance. While it is important, you can set up gears all day long with "proper" clearance and still have a lousy, noisy mesh.
Jerry makes an important point. If you have 0.010" clearance, your pinion teeth make full contact and it turns smoothly you should be good to go.
Thank you gentlemen. I just rechecked with 2 paper gaskets in place and have between .008 and .009 movement of the pinion with holding the ring stable. I have to order more shims to put the right diffy housing on. The Ruckstell bronze thrust plate was warped on this diffy as the prior owner had forgotten to put in the inner Hyatt bearing. I had it machined flat and the change in height from the left housing gave me the distance I needed to put the 12 tooth pinion in without buying a 3:1 ring gear. Even with putting a .010 and .015 shim adjacent to the steel shims near the bronze (formerly babbit) thrust washer I'm .025 short of being tight. I'll order some more shims and have to lengthen the locator pins and I think I can get it together.