North American Turbocoupe Organization



Transmission mount vibration?
Sophosis Offline
Member
#1
Has anyone encountered a vibration due to one being bound in twist after tightening? I tightened it after I got the crossmember put up and bolted in.

I had to pull the transmission back out out to fix an oil leak, so while I've got it out I want to make sure about this vibration. It comes on in 5th gear ~55-60 mph. And it is -bad-. I wouldn't dare drive it as bad as it vibrates. It doesn't do it in any other gear at the same speed. It doesn't do it in coast in 5th, only with any measure of power-on.

Since I had the input shaft cut down, I'm thinking about at least changing the input shaft bearing... it looked 100% fine and clean when I put it back together - I checked it for marks/metal chips and saw nothing that would make me suspicious enough to change the bearing.

I'm really wondering if the mount would cause the vibration.. seems sorta unlikely, but thought I would at least ask. With it out of the car, the crossmember is sitting at 75 degrees turned from normal.
1988 Turbo Coupe
- 0.020 Diamonds w/stock rods, T3 w/stock IC, BoPort 1.5 cam, LA3 w/QH on MAF, water/meth
- 5-lug swap, 31-spline, 4.10s, vacuum brakes, PBR front brakes, 2000 Mustang GT 17" rims
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Pete D Offline
Administrator
#2
This is not an area of great experience for me, but given that the problem only happens in 5th gear, I'd guess it isn't the trans mount. Could something be off in the trans?
Pete Dunham


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Dan S Offline
Administrator
#3
Sophosis Wrote:With it out of the car, the crossmember is sitting at 75 degrees turned from normal.

Can you explain this in a little more detail or take a picture of the cross member installed? Also, did you possibly change u-joints when you did the install?
Dan S
Custom 88 TC, Mandarin Copper Pearl Metallic
http://natomessageboard.com/ubbthreads.p...5#comments
1972 Ford F-100 SWB Styleside
2015 Lincoln MKC 2.3 EcoBoost AWD
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Sophosis Offline
Member
#4
Pete, that's what I'm afraid of Sad

Dan, I can take a pic when I get home, if needed. Since I tightened the crossmember-mount after I had everything back in, it essentially preloaded the mount with a twist. When I pulled it back down, crossmember attached, the crossmember settles at about a 75-degree angle from normal (closer to in-line with the trans than perpendicular, like normal).

The driveshaft is a new aluminum unit from The Driveshaft Shop. I doubt I have 1000 miles on it since installation. None of the joints felt bad when I re-installed it, but I'll check again with this specifically in mind.

Sigh.. more and more with this reply I'm beginning to think transmission internal. The vibration happens only in fifth under load. Same speed+ in 4th is no issue. Same rpm in another gear is no issue. I really didn't want to crack it open, again. I bought it used from a Mustang part-out and the guy said the trans was A-OK... but we all know how that goes. Other than this issue, it shifts beautifully.
1988 Turbo Coupe
- 0.020 Diamonds w/stock rods, T3 w/stock IC, BoPort 1.5 cam, LA3 w/QH on MAF, water/meth
- 5-lug swap, 31-spline, 4.10s, vacuum brakes, PBR front brakes, 2000 Mustang GT 17" rims
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Dan S Offline
Administrator
#5
When you re-installed the drive shaft, did you happen to turn the yoke on the rear? When installing the drive line, the splined yoke in the tailshaft of the transmission, should be 90* to the yoke of the rear end. That may be the problem area, since it's only happening in high gear when the shaft is at its highest speed. That's where I was going when I asked for a picture.
Dan S
Custom 88 TC, Mandarin Copper Pearl Metallic
http://natomessageboard.com/ubbthreads.p...5#comments
1972 Ford F-100 SWB Styleside
2015 Lincoln MKC 2.3 EcoBoost AWD
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5.0TurboCoupe1988 Offline
Posting Freak
#6
Dan S Wrote:it's only happening in high gear when the shaft is at its highest speed

the driveshaft spins the same rpm in any gear at a given speed. he said it only does it in overdrive...not in 4th at the same speed.

my guess is the OD bearing and/or the OD gear itself.
1988 TC 2.3/5-Speed, 148K
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Sophosis Offline
Member
#7
Yes, that's right.. only in 5th at the same speeds. The driveshaft was fine previously and I haven't touched the ujoints on it since they're new. Also still retains the flange mount for the rear-end.

5th gear looked fine when I had the tailshaft housing off. I spent some time with it when I counted the teeth the be 100% sure what gearing I was going to wind up with. I guess I'll pull the tail housing back off and check the bearings.
1988 Turbo Coupe
- 0.020 Diamonds w/stock rods, T3 w/stock IC, BoPort 1.5 cam, LA3 w/QH on MAF, water/meth
- 5-lug swap, 31-spline, 4.10s, vacuum brakes, PBR front brakes, 2000 Mustang GT 17" rims
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5.0TurboCoupe1988 Offline
Posting Freak
#8
while you're in there, check the output shaft bearing.....since the OD gear engages right next to it, it could also be the culprit and just not showing up until it's being driven by the OD gear.

edit: 4th gear is 1:1 so the main shaft is locked down from the input to the output shaft. that's easy on the output shaft bearing but when it's driven from the side, it puts more strain on the bearing.
1988 TC 2.3/5-Speed, 148K
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Sophosis Offline
Member
#9
Well, the mainshaft rear bearing isn't perfect, but didn't look like it was taking the beating I was feeling. I haven't taken the countershaft out yet, but I didn't like the feel/sound of the front bearing even though it spins pretty freeling, so I'm gonna go ahead and replace all four bearings.

The part that had me concerned was when I pull the input shaft out, the 15 individual bearings I couldn't move by hand.. they were wedged in there. Once I popped them out, I found a speck on one of them that seemed to be holding up that set. The other issue seemed to be I was a little too free with the RightStuf™. Found some black stuff in between the rollers on the rear main bearing.

I found a couple bearing-only kits, but I'm gonna check the bearing brands on them before I order them. They should include the individual bearing rollers and thrust bearing too.
1988 Turbo Coupe
- 0.020 Diamonds w/stock rods, T3 w/stock IC, BoPort 1.5 cam, LA3 w/QH on MAF, water/meth
- 5-lug swap, 31-spline, 4.10s, vacuum brakes, PBR front brakes, 2000 Mustang GT 17" rims
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Sophosis Offline
Member
#10
Coming back to this.. I've been wrestling with this vibration since this thread. This started after putting in the new motor and v6 trans.

Everything I went through to nail this down:
- Replaced v6 trans case and between-input/output bearings
- Pulled v6 trans, re-shimmed countershaft for zero play
- Swapped original 4cyl trans back in
- Ran the car with yoke only - smooth as silk
- Re-inspect on jack stands - sounds like it's *in* the aluminum driveshaft, but can hear/feel in rear end with screwdriver on ear
- Pulled apart rear-end and inspect, no issue found
- Last ditch, swapped out Spec 3+ clutch and put old clutch back in (stock replacement)

No more of the nasty vibration with this configuration.

This puzzles the snot out of me as the vibe was only in 5th when going down the road. I almost opted to have the driveshaft checked at The Driveshaft Shop (where I bought it at, 2hrs drive to Salisbury, NC for me). If it was fine, I was going to put new carrier bearings in the rear end. Since the sounds could also be heard at the bellhousing, I put the old clutch back in.

So now I'm left with having to call Spec, I guess... I get the feeling it's gonna be a strange conversation.
1988 Turbo Coupe
- 0.020 Diamonds w/stock rods, T3 w/stock IC, BoPort 1.5 cam, LA3 w/QH on MAF, water/meth
- 5-lug swap, 31-spline, 4.10s, vacuum brakes, PBR front brakes, 2000 Mustang GT 17" rims
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