ring gear backlash with transbrake

hi all,
Sorry if this is in wrong place, I saw some rear stuff in here so figured im ok.

anyway, question... Im building a ford 9" center section and want thoughts on backlash. The car is street driven couple thousand miles/year so I plan to use 8620 street gear in it, but it will also be launched off transbrake at times. Ballpark 800+ HP.

my question is, i know what ring gear backlash *SHOULD* be, but should I change this for the transbrake use? In my head it makes sense to make the backlash smaller for less shock on the gears, but there's lots of things in my head that sound good until they come out...

I tried to keep this short but let me know if I left out any important info.

thanks!

IMO using an 8620 street gear with a T-brake + decent power is usually just asking for trouble.

But "it is what it is" so if you're set on using a street gear anyway you could always try setting the backlash anywhere in a range between the gear maker's recommended "tight" number, down to just before finding a real/actual "bind" point when rotating the gear (as long as wear the pattern still looks OK). And then pray.

ha... i hear you... ive gone back and forth on the gear... use 9310 and check/change it every season... or 8620 and hope it doesnt grenade... ive seen/heard success stories both ways... i could still be talked into either...

thanks!...

.006 - .010" I don't think the street gears will notice the difference between a stock and strip set up.

Usually when you go on the transbrake, it takes up all the slack in the driveline, so unless the lash is excessively loose, I dont see it breaking any teeth off the gears.

hi just as an FYI.... when you footbrake a car, it will take up driveline slack, but when you're using a transbrake - thats not the case. The "lockup" happens in the trans, anything behind trans isnt affected. the rest of the driveline is just kind of hanging out chillin, until you let go of the button....

Wire the Line lock in with the Trans brake to take up the rear slack.

My TB takes up the slack. Not as much as a footbrake situation, but it does indeed put some slight pressure on it.

pmrphil wrote:The line lock is plumbed only to the front brakes - how can that possibly affect slack in the driveline? I don't think street gears will be an issue, unless the launch RPM is to the moon. 4,000 - 4,500 shouldn't kill it too quick unless you're launching a tank. No change is needed in backlash, IMO.

When you roll into the staging lights you apply the brakes, which has taken up ALL the slack in the driveline and with the line lock and Trans brake wired together the line lock holds the car in position while the trans engages reverse. The car doesn't rock because of the sloop in the rear end. Try it you might start to go some rounds.