true trac

I installed the true trac and wanted to know if the noise it's making is normal. Driving down the road it's about the same sound that the trans makes when you go kinda fast in reverse......sort of a humming/whining. My best guess is since it's a fully gear driven unit that the sound its making is normal. It drives very smoothe and I can't feel it slipping when I go around corners. I would like to know what the overall normal operation is for the true trac and if it's supposed to make any noise, what exactly? Any thoughts?

No its not supposed to make any noises. Backlash is usually set wrong in most cases.

The gear set up is probably off.

If the backlash is set wrong, how do I correct it?

Tell whoever installed it to fix the backlash... or else you will be replacing the whole thing shortly!!!

pinion depth is most likely off.

Turns out it was shimmed wrong but it's good now. The dial indicator measured 0.009" of backlash and the pattern check showed that the ring and pinion were meshed perfectly.

so what is it set to now?

0.009" is too loose....especially if the gears and bearings are new.

what are they supposed to be set to, mine started at .005 and after 500 miles or so they are at .009 now should i re-shim them?

That's on the loose side for sure. It all depends on if they're GM gears (5 or 2 cut) or aftermarket. The newer style GM gears like to run tighter. I would use the manufacturer's specs on aftermarket gears.

The reason I said 0.009" was loose for new gears is because of the wear in you experienced....so they'd end up in spec. I doubt you'll gain any more backlash after 500 miles. I like to keep them under 0.008" but others might have a different idea.

well...they are aftermarket and they cam with no specs, i think they need tightened up cuz now i can hear a slight "whistle" about 55 mph

The way to do that now is re-shim and use a new sleeve (unless you have a solid spacer). You might get awat with adding 0.001-0.002" to the pinion shim but check the pattern because changing the pinion shim to tighten the backlash will also slightly change the gear mesh by moving the pinion into the ring.

Let us know how it goes.

it measures 0.009" of backlash as of right now but all I did was replace the open diff with the true trac, I did not change the ring gear or pinion.

There's still a slight amount of maching difference in the carrier. Did you use new bearings? I hope so and if you did, it's on the loose side because they will wear in a little.

well...after talking to some guys last night they said feel of the diff cover after you drive like 5 min around the neighborhood and if it is pretty hot your back lash is set wrong,

and mine was pretty hot, along with them making a slight noise, so mine are coming back apart this weekend!

I did use new bearings and it turned out the factory shims got it where it is now. I used the thicker shim on the side with the ring, so the ring and pinion are as tight as they can be with the factory shims. A friend of mine said that as long as the backlash is between 0.008" and 0.012" it is good and I'm at 0.009" now. I took his work for it cuz he has done countless rear ends and his Nova is EXTREMELY fast!! After we did the pattern check, the clean spots on the ring were dead center. As for the pinion, we didn't touch it aside from rotating the yoke to do the pattern check.