"Play" in Rear Differential

buildone · #1 (**permalink**) 03-16-2011, 04:52 PM

How much rotational "play" should you have in an IRS rear differential with TrakLok? I have about a 1/4" as observed at the pinion flange. I assume this is a function of "backlash" setting? I really feel it, especially in 5th gear.

Thanks!

LMH · #2 (**permalink**) 03-16-2011, 07:26 PM

You have a 1/4"?...! Wow! Is the pinion flange nut loose? That needs to be set up with the correct gear pattern. I would take it to someone who knows how to set that up correctly.
Larry

buildone · #3 (**permalink**) 03-17-2011, 05:24 AM

Oh man! I sure wish I'd known to check this before putting it in the car.....live and learn I guess! The guy I had put the traklok in was a Mustang mechanic

Does it have to come back out of the car to correct?

Really appreciate it.

LMH · #4 (**permalink**) 03-17-2011, 06:33 AM

It depends on what's in the way and access to the rear cover, pinion flange etc. I would probably take it out being that it's IRS and take the differential to a local shop.
Good luck!
Larry

redmt · #5 (**permalink**) 03-17-2011, 06:42 AM

1/4" rotational or 1/4 turn? As in say on a clock , from 12 to 1 or from 12 to 3? If your talking 1/4 turn as in from 12 to 3, pull it and rebuild it

buildone · #6 (**permalink**) 03-17-2011, 07:16 AM

Quote:

Originally Posted by redmt

1/4" rotational or 1/4 turn? As in say on a clock , from 12 to 1 or from 12 to 3? If your talking 1/4 turn as in from 12 to 3, pull it and rebuild it

It's about a quarter of an inch "rotational" measured at the outer edge of the pinion flange.

Jerry Clayton · #7 (**permalink**) 03-17-2011, 09:47 AM

backlash is measured at the ring gear, not the pinion flange---pull the rear cover(I'm assuming ab ford 8.8 gear?) and check the backlash correctly--typcily it will be .008-.012 and that will be quite a bit of rotation on the pinion

redmt · #8 (**permalink**) 03-17-2011, 11:29 AM

Quote:

Originally Posted by buildone

It's about a quarter of an inch "rotational" measured at the outer edge of the pinion flange.

I wouldn't worry about it too much. As Jerry C said though , the correct measurement is taken at the gear set. If you are getting drive line / gear slop that you can hear or feel in 5th gear, I would look for something else besides the rear end. Depending on the miles and abuse its had it could just be a collective "slop factor" in everything. If everything is reasonably tight, I'd be looking at the gear set and main shaft uin the tranny.

LMH · #9 (**permalink**) 03-17-2011, 12:26 PM

Pull it and fix it. Then it's not a problem that leads to other problems. That's my opinion.
Larry

redmt · #10 (**permalink**) 03-17-2011, 12:46 PM

Quote:

Originally Posted by LMH

Pull it and fix it. Then it's not a problem that leads to other problems. That's my opinion.
Larry

FIND it and fix it. If it ain't broke you can't fix it. One test he might try is to lock up the rear brakes and rotate the drive line both in and out of gear. Then raise the rear wheels off the ground, release the brakes and do the same test. That will at least tell you what direction to look for the slop. If you get more slop with the rear end raised then it's in the tranny or even possibly the clutch drive hub. He needs to isolate the problem first.

ubeturas · #11 (**permalink**) 04-05-2011, 02:07 PM

used differentials

Quote:

Broadly speaking, there are three input torque states: load, no load, and over run. During load conditions, as previously stated, the coupling is proportional to the input torque. With no load, the coupling is reduced to the static coupling. The behaviour on over run (particularly sudden throttle release) determines whether the LSD is 1 way, 1.5 way, or 2 way.

If there is no additional coupling on over run, the LSD is 1 way. This is a safer LSD: as soon as the driver lifts the throttle, the LSD unlocks and behaves somewhat like a conventional open differential. This is also the best for FWD cars, as it allows the car to turn in on throttle release, instead of plowing forward.[2]

Locking differential
Main article: Locking differential

buildone · #12 (**permalink**) 05-23-2011, 04:12 PM

Thanks, guys. One thing I did do was try to evaluate it by rotating the drive shaft by hand with the car in and out of gear, and the rear wheels off the ground. With it in gear, the pinion flange hardly moved at all (meaning the transmission is ok?), and with it in neutral, I get the 1/4" rotational movement of the pinion flange. I had also read as mentioned above that the correct backlash should be .008 to .012.....I was just wondering if anyone knew what that would translate into at the pinion flange. I did check to see if there was any play in the U joints, and if the driveshaft to pinion flange bolts were loose.......both seemed to checkout ok.