My 88GT 5spd has a vibration that starts at about 3300 rpm and continues up to the redline. I feel it it the shifter first and then as the revs climb, in the rest of the car. It's not terrible but it's definitely there. Around town, under 3000 rpm, under load or just cruising, its smooth as can be. It does not vibrate if it is free revved out of gear or if you push the clutch in at speed, so I'm guessing it's not in to engine. The trans is a pretty new T5Z (not abused or power-shifted, I bought it new in the crate) and when I put a clutch in with the trans, I did put the alignment dowels in place on the flywheel too. Any suggestions? Thanks.
Help With Driveline Vibrations In 88gt
- Thread starter 92LX5spd
- Start date
Jason 302
10 Year Member
You can take it to a driveshaft shop and have it balanced. It helped my stocker out. New U-joints wouldn't be a bad idea either, if they haven't been replaced.
Best thing to do is drop the coin on an aluminum one from FRPP or DSS. Not only are they balanced, but aluminum absorbs the vibrations much better.
You can also try mounting the driveshaft in different positions on the rearend flange. Like unbolting it, turning it 90*, and bolting back on.
Best thing to do is drop the coin on an aluminum one from FRPP or DSS. Not only are they balanced, but aluminum absorbs the vibrations much better.
You can also try mounting the driveshaft in different positions on the rearend flange. Like unbolting it, turning it 90*, and bolting back on.
I think the aluminum driveshaft is a good idea. I'm wondering if that is the culprit though since the vibrations are loaded engine rpm dependent and not road speed dependent. Not trying to argue, but just trying to get my head around the problem. Either way, I do want to get an aluminum driveshaft.
mikestang63
SN Certified Technician
draw a line down the length of the driveshaft with a white grease pen and then spin the driveshaft.. it could also be a little twisted.. or the u joints worn.
Jason 302
10 Year Member
That's why I suggested replacing the u-joints too. They might be binding or something while under load. But you're right, driveshaft spins faster with wheel speed, not rpms.
Jason 302
10 Year Member
Good to hear. Which brand did you go with, Ford Racing? That's one mod I haven't done to my car yet that I would like to eventually.
I had issues with mine as well, did the summit aluminum driveshaft which calmed it down a bit then put it up on jacks and found one of the drums was rubbing, was especially shaky under heavy braking or slowing down over 60 mph. Went to discs in the rear and everything is better....except my e-brake 
Loose/misaligned u-joint could cause it also messing with the flexplate in any way. Motors are externally balanced so adding/removing weight or getting a perfectly balanced flexplate will cause vibes....
Loose/misaligned u-joint could cause it also messing with the flexplate in any way. Motors are externally balanced so adding/removing weight or getting a perfectly balanced flexplate will cause vibes....
If you didn't have the clutch assembly and flywheel balanced together when you installed the new clutch, that could also be a source of your issues.
Rules out the flywheel, but not the clutch. This is why it's been recommended to balance then as an assembled unit.
The clutch/flywheel is not likely the issue. I was just making making clear the point that the the two should still be balanced as a unit, regardless of the brand, or newness.
Driveshaft could be a likely culprit. Don't disregard wheel balance either.
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