Rear axle misalignment..

[GodAmGT00]

I've posted this on another forum, but I figured I'd give here a try..

Well, in my quest to figure out why I get such nasty drivetrain vibration, I've gone through a lot of variables, and still haven't been able to pinpoint an exact cause, unless...

Last night, when I was checking out my rear tires, which have been only rubbing on one side (yes, I haven't rolled my fenders yet, so sue me..), I noticed that the Passenger's side sticks out nearly a half inch past the fender... I run to the other side, and notice that my 315/35R17's are actually a half-to-a-whole inch tucked under the fender.. WTF?!?!?!?

SO in my mind, my rear axle is pretty far off from what I believe to be normal. I would have never seen that much of a discrepancy w/ my old tires/rims...

Since I've swapped U-joints, had the rear axle rebuilt, and rebuilt again, complete suspension overhaul, NEW tires/rims, and new tranny mount, I couldn't for the life of me find out what was causing the vibration... Now I think I know..

Now here's the "meat and potatoes." Since panhard bars are used to center the rear axle on the chassis, this sounds like the only approach I have to straighten things out; no pun intended..

Question I have is, since I have a rear-diff girdle, it looks like a panhard may not work. Has anyone else used a panhard bar along w/ a rear diff. girdle w/ success?? Before I make the plunge, I wanna know if it'll work..

TIA


JT

 

[bdcardinal]

u have the Maximum Motorsports Panhard bar with the FRPP diff girdle. its tight, but it fits. the chassis mount covers the fill and drain plugs, so when i do have to service the diff, it will be interesting.

 

[flexiclese]

I use a MM PHB with a TA girdle, TA just released the girdle in the last year we recessed load bolts to clear PHB's. Part # 1806 I think...

 

[GodAmGT00]

Mine has the recessed load bolts, so I think I should be okay, but as was mentioned, the drain and fill plugs are going to be in the way I believe... Maybe not.. It may only need the torque arm removed...

What are your guy's impressions of the MM Panhard bar??

Does anyone make Watts Links for our cars?? If so, can I even use Watts Link w/ the Rear diff. girdle??


JT

 

[bdcardinal]

i think Griggs might make a watts link. i was up at Buttonwillow Raceway for the SVTOA event. both Maximum and Griggs were there. i didnt get to check out Griggs booth, but Maximum was absolutely awesome. my driving instructor holds the lap record for Buttonwillow in the configuration we were running. he has an AIX car with all MM parts, and said something didnt feel right on mine. we took it to Maximum's pit stall and they proceeded to counterweight my car for free!!!! the owner and all teh employees are totally badass.

 

[CdnNavybob]

Evolution motorsports also makes a watts link for out cars. Never heard much feedback on it though...

 

[GodAmGT00]

Sweet.. I'm going to check out Griggs/Evolution, since I've seen the MM Panhard bar already... I'm willing to bet though, that I may not be able to use the Watts..

I really have to do something about this soon since I think my pinion gear is pretty much done.. After the fluid add the other night, the sound hasn't really toned down... What's worse, is that this will be the 3rd time in 2 years I'd have to rebuild the diff... I'm going to wait until I get the suspension/drivetrain issues ironed out..

Thanks for all the help guys...


JT

 

[stangman98]

What gears are you running? Alot of the time if you are running 4.10's or better you will get vibration if you do not have an aluminum driveshaft. Also, are you sure the backspacing on the wheels are perfect on both sides? Just adding a Panhard bar may not help the issue. Have you looked at your torque boxes to make sure those are in good shape? That could also be an issue.

 

[GodAmGT00]

Currently, I have 3.73's w/ the Eaton 31-spline LSD, T/A Diff. girdle, and all of the other suspension stuff.. I was doing some research, and I saw that some of the newer Mustangs were experiencing some of the same problems, w/ bigger than normal axle offsets from the factory.

Excellent points.. I haven't checked the torque boxes, since I've been so busy w/ work, school, more work, then my other job... I plan on getting under the car tomorrow... As far as backspacing, I'll pull the wheels off tomorrow and measure it, although they seem to be pretty true. They also almost balanced out perfectly. Here's another point of interest...

I got into an accident last year, however, the vibration was neither worse, nor better than it is now... Originally, the shop who rebuilt my diff the first time, didn't bother to shim the diff correctly, and ate the bearings in a matter of a year.. I replaced U-joints and the tranny mount.. The tranny mount actually got rid of some of the vibration, but the U-joints, I think are no good. I get a squeak when the car shifts... I think it's just a big mess of the rear..

On top of this, I think the breather valve is stuck open, because I seem to be puking fresh gear oil (Mobile 1 @ $12 a quart, Friction Mod @$5, Sonofabitch) at an alarming rate.. Also, the pinion seal looks like it's leaking, due to the vibration, I can only assume..

I may also bring it to an alignment shop to see if they can at least get me some raw data to work w/..


JT

 

[LI98GTStang]

Did you remove your dogbone at one time? I know for most people, removing the dogbone doesn't do anything, but some stangers have posted that they get vibrations with it off. Maybe worth diggin up in the backyard and trying if you still have it around.

 

[GodAmGT00]

Well, I've never removed the dogbone, so I can rule that out..

Yesterday, I removed the rear wheels, and the backspacing is spot-on on both wheels... I didn't really get to dig too deep, as to the torque boxes, and hopefully, if it doesn't rain until later today, I can check them out...

3 days, and the rear axle is already out of fluid from the breather..



JT

 

[spederman]

I had the same problem last year. I started to look at GT's in parking lots when i would walk by and i would say most Gt's had the same problem. And it was always on the same side. So i wondered if maybe it had something to do with the torque of the cars. But anyway, I had the Ford body shop put the car on the laser frame straightening measuring machine thing. They used the lasers to find out how much the rear end was actually off, and ended up unbolting the whole rear end from the car, moving it over whatever it required and rebolting it down. Its been staying put so far. But i never had a vibration anyway, it was just something I noticed one day and my OCD started annoying me so i had to get it fixed.