Help With Driveline Vibrations In 88gt

9

92LX5spd

15 Year Member

Feb 23, 2013

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Mar 6, 2016

#1

• Mar 6, 2016

• #1

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.

 

Jason 302

10 Year Member

Aug 9, 2003

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Mar 6, 2016

#2

• Mar 6, 2016

• #2

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.

 

Reactions: Davedacarpainter

9

92LX5spd

15 Year Member

Feb 23, 2013

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Mar 6, 2016

#3

• Mar 6, 2016

• #3

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

Aug 27, 2012

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Mar 6, 2016

#4

• Mar 6, 2016

• #4

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

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Mar 6, 2016

#5

• Mar 6, 2016

• #5

92LX5spd said:

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.

Click to expand...

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.

 

9

92LX5spd

15 Year Member

Feb 23, 2013

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Mar 11, 2016

#6

• Mar 11, 2016

• #6

Well, I got the aluminum driveshaft in and things are much improved. I can still feel some vibes in the shifter over 3000 rpm, but less. Then again that might just be normal for a non-insulated shift handle. The rest of the car is smooth up through the revs. A nice improvement. Thanks.

 

Jason 302

10 Year Member

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Mar 11, 2016

#7

• Mar 11, 2016

• #7

92LX5spd said:

Well, I got the aluminum driveshaft in and things are much improved. I can still feel some vibes in the shifter over 3000 rpm, but less. Then again that might just be normal for a non-insulated shift handle. The rest of the car is smooth up through the revs. A nice improvement. Thanks.

Click to expand...

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.

 

Jace_78

Member

Mar 10, 2016

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Mar 11, 2016

#8

• Mar 11, 2016

• #8

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....

 

Gearbanger 101

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Mar 11, 2016

#9

• Mar 11, 2016

• #9

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.

 

9

92LX5spd

15 Year Member

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Mar 12, 2016

#10

• Mar 12, 2016

• #10

I did go with the Ford Racing driveshaft. Took longer to put the car up on stands than it did to put the 'shaft in. Nice and easy. I did not have the clutch and flywheel balanced together but did put in a new Ford flywheel with my new clutch.

 

Jace_78

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Mar 12, 2016

#11

• Mar 12, 2016

• #11

Did you make sure your flywheel was the proper offset for your motor?

 

madspeed

Colonel Mustard

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Mar 12, 2016

#12

• Mar 12, 2016

• #12

you mean imbalance? ie 28oz, 50 oz or zero balance

 

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92LX5spd

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Mar 12, 2016

#13

• Mar 12, 2016

• #13

The one I bought is the direct Ford replacement for the original factory flywheel. The Ford part numbers are the same on the new one from the original one I removed.

 

madspeed

Colonel Mustard

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#14

• Mar 12, 2016

• #14

ok, that ca rule out flywheeissue unless your motor was rebuilt and balanced differently

 

Jace_78

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Mar 12, 2016

#15

• Mar 12, 2016

• #15

madspeed said:

ok, that ca rule out flywheeissue unless your motor was rebuilt and balanced differently

Click to expand...

Ya I meant imbalance, early post no coffee couldn't think of right word lol

 

Gearbanger 101

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#16

• Mar 12, 2016

• #16

madspeed said:

ok, that ca rule out flywheeissue unless your motor was rebuilt and balanced differently

Click to expand...

Rules out the flywheel, but not the clutch. This is why it's been recommended to balance then as an assembled unit.

 

9

92LX5spd

15 Year Member

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Mar 12, 2016

#17

• Mar 12, 2016

• #17

But wouldn't an imbalance in the flywheel/clutch show up when free revved up in neutral? The engine free revved smoothly up past 4000rpm. The condition was only noted in gear, at speed under load.

 

Gearbanger 101

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#18

• Mar 13, 2016

• #18

92LX5spd said:

But wouldn't an imbalance in the flywheel/clutch show up when free revved up in neutral? The engine free revved smoothly up past 4000rpm. The condition was only noted in gear, at speed under load.

Click to expand...

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.

 

Jace_78

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Mar 13, 2016

#19

• Mar 13, 2016

• #19

I put mine on Jacks and revved neutral and then in gear, became apparent u joint was not centered.