Recently replaced my differential and had it built by a very reputable shop for my '66 stang. Had one of the axle bearings replaced as well.
The differential is a ford 8 inch. I went from a 2.80 open gear to a 3.80 trutrac and now after 70mph and up I get a VERY bad shaking/vibrating. It gets worse as I speed up.
I can feel it coming up from the shifter and it seems to be coming from the back of the car. There is no whining or any abnormal noises, just a very violent vibration.
The shaking is absolutely ridiculous. I had the drive shaft balanced and new ujoints put in a while back. I did however accidentally start the car while it was in gear (Car was on jack stands no wheels on) and the driveshaft spun around a bit and flicked off the little caps into a tub of gear oil. Nothing seemed wrong and I simply popped them back on. I don't think it was serious enough to do any damage especially since it was such a short period of time, I just thought that could be helpful information.
Motor mount bolts also seem a little loose, but they've been like that and I didn't have a problem before.
The only real different thing other than that is the new tire I had put on. It's the exact same tire as the rest and I had all of them balanced.
I had the drive shaft balanced and a new u joint put in a while back and everything was fine until now. However the car was accidentally started while in gear on jack stands and the driveshaft bounced around a bit. The u joint end caps are fine though. Could that have bent or damaged the drive shaft?
Opinions? My morale has gone down because I just started driving the car again after two months and this is happening
I'd have the driveshaft checked out to be sure it didn't bend a bit. As for the gear oil, that likely contaminated the grease and caused the needle bearings to burn up. Gear oil is obviously thinner than bearing grease. I would have cleaned out the caps, and repacked them before installation. I'd also recheck the drive train angles.
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Check the balance of the driveshaft first, then also check tire balance. An out of balance driveshaft can set up an awful vibration especially if a harmonic is arrived at.
Wow you guys are fast. The other forum took FOREVER for a reply. I'm wondering if
I can drop my car off instead of pulling the drive shaft myself, filling up the t-5 I have is major pain. Would a bad driveshaft get steadily worse after a certain speed?
In the case it's not the driveshaft, what else comes to mined?
It actually takes surprisingly little "funkiness" in a U-joint to have issues.
(for instance, if you were missing some of the roller bearings out of a
cap, you WILL have vibration issues)
You'll be looking for a bent DS and taking a real close look at the U-joint.
Here's a vibration chart.....
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I would check and make sure all the needle bearings are in the ujoint caps. If those are OK then take the shaft to the shop and have it check. If that all checks out then it's probably in the differential.
So it seems that we can narrow it down to the driveshaft/ujoints? I checked the caps and all bearings seem to be accounted for. I also rotated the driveshaft 180 and snugged it back down, didnt help. I'll drop by south bay driveline and have them take a peak. I had them do work on the driveshaft before and they did an excellent job.
Would the plunge into gear oil be that bad for the ujoints?!
Get the driveshaft checked it might even be the u joints because i had a vibration last year and when i changed the ujoints it went away. Also jack your car up and let the wheels spin see if the wheels or axle flange wobbles. One of my cars had a les over 30 thousandths out of round, i replaced the axles and no more vibration. These can be annoying to isolate but do not give up
So it seems that we can narrow it down to the driveshaft/ujoints? I checked the caps and all bearings seem to be accounted for. I also rotated the driveshaft 180 and snugged it back down, didnt help. I'll drop by south bay driveline and have them take a peak. I had them do work on the driveshaft before and they did an excellent job.
Would the plunge into gear oil be that bad for the ujoints?!
South Bay Driveline has done good work for me as well. Keep us posted on the outcome.
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*67 Vintage Burgundy 390GTA with most of the bells and whistles*
With all the mention of the driveshaft and I agree with everyone, I bet it is the tire. Even if they were all balanced doesn't mean that they were all balanced exactly the same (not trying to speak poorly of someones work).
More than likely if it were the driveshaft your vibration would be there mostlikely at any speed, where as a tire, if not balanced properly for speed will start to give a vibration when it's balanced speed is exceeded.
I just had the driveshaft rebalanced and straightened. Steve at south bay driveline is an awesome guy, he did it free of charge! I've taken my driveshaft to him before and he does excellent work.
However I'm still having the same problem! I think I'm going to take the car to another shop and have the wheels rebalanced. I can see some weights actually falling off my wheel.. One thing to note that even in neutral the problem still exists at speed.
Last edited by happystang; 01-28-2013 at 02:39 PM.
You've probably eliminated the driveshaft as being an issue (but it is
still turning in neutral)......
Uneven tire wear, rim/s with runout and a possible tire balance issue
are your next places to look.
I had an 9" axle shaft runout issue in my race car one time that required
pulling them and straightening. They were Factory factory pieces. Ok at
speeds that most passenger cars drive but at 130+ it was really pretty
obnoxious.
__________________
As the drill sergeant said, "I taught you everything you know. I didn't teach you everything I know."
"Human beings, who are almost unique in having the ability to learn from the experience of others, are also remarkable for their apparent disinclination to do so."
- Douglas Adams
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HORRIBLE vibration after 70mph
