Need thoughts on backlash

Doug Domm · 09-06-2009, 09:35 AM

We are replacing gears in a GM 8.5 inch 10 bolt. They are Richmond 4.88 and call for .010 backlash. We can get .012 and .008 with the shims we have now. This is a transbrake application in a 3300 pound car. What is an acceptable plus or minus from Richmond's .010 and would you use a tighter backlash with a transbrake? Thanks Doug

Alan Roehrich · 09-06-2009, 09:44 AM

The pattern is more important than back lash, but back lash is better on the tight side, so long as it does not bind. Check to make sure that it does not have a spot that binds or gets tighter than 0.002-0.004, and you'll be fine at 0.008.

Doug Domm · 09-06-2009, 12:20 PM

Alan, thank you very much as you just confirmed my thoughts. And thank you to Classracer for this forum, it has served me well and is an excellant tool for resources. Doug

X-TECH MAN · 09-06-2009, 02:52 PM

I agree with Alan.....I use .004 at the tightest spot when checking and set the pinion so the tooth pattern is closer to the inside of the ring gear than in the middle in a drag race application. Under a load the pinion tries to move toward the outside of the ring gear which could cause chipped and broken teeth.

09-06-2009, 09:35 AM	#1
Doug Domm Member Join Date: Apr 2006 Location: canada Posts: 250 Likes: 28 Liked 84 Times in 21 Posts	Need thoughts on backlash We are replacing gears in a GM 8.5 inch 10 bolt. They are Richmond 4.88 and call for .010 backlash. We can get .012 and .008 with the shims we have now. This is a transbrake application in a 3300 pound car. What is an acceptable plus or minus from Richmond's .010 and would you use a tighter backlash with a transbrake? Thanks Doug

09-06-2009, 09:44 AM	#2
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,066 Likes: 1,487 Liked 1,630 Times in 378 Posts	Re: Need thoughts on backlash The pattern is more important than back lash, but back lash is better on the tight side, so long as it does not bind. Check to make sure that it does not have a spot that binds or gets tighter than 0.002-0.004, and you'll be fine at 0.008. __________________ Alan Roehrich 212A G/S

09-06-2009, 12:20 PM	#3
Doug Domm Member Join Date: Apr 2006 Location: canada Posts: 250 Likes: 28 Liked 84 Times in 21 Posts	Re: Need thoughts on backlash Alan, thank you very much as you just confirmed my thoughts. And thank you to Classracer for this forum, it has served me well and is an excellant tool for resources. Doug

09-06-2009, 02:52 PM	#4
X-TECH MAN Banned Join Date: Dec 2007 Location: Lake Placid, Florida Posts: 3,203 Likes: 1,047 Liked 235 Times in 110 Posts	Re: Need thoughts on backlash I agree with Alan.....I use .004 at the tightest spot when checking and set the pinion so the tooth pattern is closer to the inside of the ring gear than in the middle in a drag race application. Under a load the pinion tries to move toward the outside of the ring gear which could cause chipped and broken teeth.