trax

iTrader: (2)

I put my 9-inch together myself last summer. I've got a C7AWE case, a set of Richmond 4.10's, and a Daytona pinion support in a Moser housing. All bearings are brand new.

I carefully shimmed and checked the gears using a dial indicator, and the pattern looked great. I put 100 gentle miles on the rearend to break it in, and the thing was DEAD QUIET. No whine, nothing. Quiet as a stock 10-bolt. Ok I thought, good job for me.

However, this past weekend at the drag strip, I made several 5000 RPM launches on my BFG drag radials. As soon as I hit the brakes to go to the return lane, I noticed that the gears were howling like crazy on deceleration. On the road I've noticed that it's loudest below 40 MPH. Acceleration and steady cruise is a much quieter, but still quite noticeable whine. The sound didn't seem to change or get worse between runs.

So help me understand what happened here?

My car runs mid 12's, so I find it hard to believe that the car's power levels are causing physical damage to the rearend... I'd find it much more likely that I botched something in the gear setup and it wasn't evident until I started abusing it.

I haven't pulled out the center section to take peek yet, but here is my semi-educated guess. Please let me know if I'm way off base here... I'm always learning

1. Since a 9-inch carrier is held in place by adjusting nuts (the phone-dial things) which have retention clips of their own, I would wager that the force of the launch would not affect the side-to-side location of the carrier.
2. Similarly, the pinion depth is dictated by the shims between the center section and the pinion support. The pinion cannot physically move further away from the ring gear since the inner pinion bearing and race keep it from pulling out.
3. HOWEVER, if the pinion nut was able to back off just slightly from the force of a launch, this could introduce slack between the outer pinion bearing and the flange of the yoke, which keeps the outer pinion bearing in place. If the outer pinion bearing was allowed to back off just slightly, this could allow for some slop in the pinion location.

Does this idea have any grounding in reality?

Thanks!

MCBRIZ28

iTrader: (2)

If you used the regular style pinion bearing preload crush sleeve I bet it has collapsed a little opening up the backlash causing the whine. If you have the aftermarket solid preload spacer I am like you pinion nut back off some how and open up backlash.

DAVESS02

iTrader: (30)

I've seen cases that had the treads pulled where the adjusters are. I'd think checking the backlash would be a good place to start regardless of what your problem is.

Billiumss

iTrader: (11)

You have Richmond gears..... They are known for gear noise.

trax

iTrader: (2)

MCBRIZ28 -- I'm using a solid pinion spacer.
DAVESS02 -- I'll run a pattern tonight if I get time and I'll post some pics.

DAVESS02

iTrader: (30)

I'm mainly curious to see if the lash has increased. If the adjuster has moved, you'll have lots of slop between the teeth.

TJ

iTrader: (10)

its 4.++++ and its a richmond. with a lil abuse they make noise.
i had a ford factory gear with .028 of slop and it never made one single noise.
been abused since the 70's, im sure, and ive put numorous launches on it.
im on my 3rd 4.33 gear, and it still makes noise around 50mph.
i think its the nature of the beast.

trax

iTrader: (2)

Well I finally had time to get to the garage. Took 90 minutes to go from a running car to a center section sitting on my workbench. I'm gonna take a break for dinner... then I'll post up a ton of pics with some patterns and photos of the backlash measurements.

trax

iTrader: (2)

Ok, something's not right. I just checked backlash: .004".

First, some pics of the mounting angle of the dial indicator:


And the lash reading:


The adjuster screws:


I can't find my notes from when I assembled the gears but I want to say I had something in the neighborhood of .008-.012 like in this article.

Taking a step back, when I installed the gears, I never properly set preload on the carrier bearings. I snugged the adjuster nuts, verified lash, then cranked them before putting in the locks. I verified that backlash was unchanged, then called it a done job.

However, I didn't consciously set the adjusters for an additional .004"-.006" of snugness.

Could that be the problem?

trax

iTrader: (2)

Update -- I reset lash to .009", reinstalled the rearend, and verified proper pinion angle. Noise persists on decel, with no noticeable change from before. Acceleration and cruise make almost no noise. So I'm still not sure what's going on.

Any other stuff I can try before I buy another ring and pinion?

Jawsgear

iTrader: (2)

You need to run a pattern on the teeth so we can see what the depth looks like. Also take a closer pic of the teeth on the ring gear, drive side and coast side so we can verify the gear did not get hot and burn up. Did you check the pinion bearing preload while you had it out, if so what was it?

Jeff

trax

iTrader: (2)

Jeff,

The rearend is in the car again so that will have to wait for the weekend. What does a burnt-up gear look like? Also, I didn't check the pinion preload since I don't have a dial torque wrench. Is there another way to check it?

Thanks