Topless Stang

Sort of a misleading title....but here goes

I purchased a takeoff 8.8" rear w/4.10s and the cobra pinion flange preinstalled from Blue Oval a little while ago. I finally got around to installing it back at the end of April. After install it was great, but my work commute was less than 5 miles round trip and I didn't put any serious miles on it. Fast forward to June...I relocated for a new job and put jus over 900 miles on he car. Sometime during those 900 miles I developed a horrible vibration/grinding sound when accelerating. It's almost unbearable from 20-45 mph, but it dies down just a little once you get to higher speeds. I'm thinking that the gears weren't installed correctly or the pinion nut wasn't dont right...but I'm breaking down and putting it in he shop tonight.

My question is this....instead of paying for the gears to be fixed (by possibly redoing the shim) should I just have new gears installed? I know that if the gears have worn wrong then I'll have to get new ones installed anyway. I just don't want to pay the laor to try to fix it, only to end up having bad whine due to improper wearing. I'm also on the fence about my gear ratio. Having the 4.10s was nice, but during any highway driving it sounded like I was running the motor pretty hard, not to mention I can almost see my gas gauge move if I stand on the pedal. My car is a DD/Street car first. It will see track time, but I'm not looking to set any records with my six banger either. I guess what I'm asking is if I should step down to 3.73s. I have an auto with a ProCharger Stage II kit installed and from what I read autos with a blower do really well with 3.73s, plus highway driving is much better. My situation is a little different, so after reading several gear threads I decided to start my own. What do you guys/gals think?

jimkaray

I thinking you might have a bad bearing. You've got plenty of added torque with the s/c so you might be a happier with the added top end of the 3.73's.

Topless Stang

Holy crap...I haven't talked to you in quite some time Jim. How have u been? The guy at the shop I'm going to took it for a short ride on Saturday and he told me hat might be the problem too, but he won't know until he gets it broken down. If its that then the repair won't be pricey at all and I may wait on getting different gears. I just felt like I was really over driving the car when it was on the highway. I just get nervous when my tach starts to sit at 3-4000....other than that I love the 4.10s over the stock gears.

How do bearings like that go bad? Could it have been a faulty install?

jimkaray

I'm hangin' on there. Just been finishing up working all day into the night adding some sound deadener plus rewiring and mounting new switches in the console for my nitrous set up. Came out nice just have to finish up the hook ups for the bottle opener.
A number of ways a bearing could fail, in your case I'm guessing defective part possibly or improper installation. No or low lube or maybe even lubea poor quality. Of course they wear out with high mileage.
FYI...If you decide to make a change I've got a set of 3.73's I should get rid of now that I've committed to the 4.10's. I swapped out the OD gear for better cruising RPM when I had my trans rebuilt.

wcgman

It might be too late, but I'd consider draining the pumpkin and checking for any metal fragmentation (might be too small to see) and refilling making sure that friction modifier is definitely added to the mix.

Topless Stang

Thanks for the heads up. They drained the fluid and found metal everywhere, so they also have to flush and clean the axle tubes. They're being thorough, thats why the price is a little higher than a standard gear install.

wcgman

Sounds like you found a good shop. I wouldnt worry too much about the cost if I were you. I had a rear end go out on me where the splines on the axles just wore out or sheared off. Ended up having to roll it down the hill and let it rest against a tree because the parking brake cables were shot and with no rear end, park didnt even work. That was a crappy week indeed.

Topless Stang

Now that would suck....thankfully nothing like that has happened to me. I would go thru that and then some if it meant I would be the proud owner of a GT500 in the end

808muscle

Did your noise sound anything like mine? I believe mine is a crush sleeve or pinion bearing failure. I just ordered new 4.10s and a Motive install kit. Last year when installing a trutrac I just ordered a generic bearing install kit of ebay....... Possibly got some crappy parts.