Vibration

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FL.40

Member
Joined
Oct 28, 2012
Messages
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Location
United States
My Car
1973 Mustang Coupe 351W T5
Gents, I have a question for the collective.

Upon purchase of my Mustang I noticed the speedometer did not function.

I did a little surfing on the net and came to the conclusion the speedo gear had came loose from the shaft of my T5 transmission. So I ordered a new clip and set off on pulling the trans. I pulled the tail shaft housing, installed the new clip and reinstalled the tranny , along with a new cable, new polyurethane tranny mount, and Mobile One synthetic ATF.

Now the problem, I have a very bad vibration at about 2500 RPM( Sorry I dont have a tach yet to give a exact RPM).

I have previously put new u joints in and ran fine, so I can rule those out.

I have put about ten clutches in different cars over the years so I think I am not a rookie at this. But I can't figure this one out.

I did not pull the bell housing or clutch. Could I have bound something up upon install? Bad pilot bearing? Could I have thrown the drive shaft out of balance, somehow?

Any ideas or suggestions would be very beneficial.

Jeff

 
Check all bolts. If they are tight try reinstalling the rubber transmission mount. If it goes away, you're done. Just an idea. Chuck

 
Like Chuck said ,i would check the new mount. They like to cause some vibration because they are so hard. Swap it with the old one just to rule it out.

 
Like Chuck said ,i would check the new mount. They like to cause some vibration because they are so hard. Swap it with the old one just to rule it out.
Put on a rubber mount, poly trans mounts transfer all vibrations into the frame. they should be marketed for racing use only.

 
Like Chuck said ,i would check the new mount. They like to cause some vibration because they are so hard. Swap it with the old one just to rule it out.
Put on a rubber mount, poly trans mounts transfer all vibrations into the frame. they should be marketed for racing use only.
Hard to believe...but firmer is not always better.

 
Thanks for the reply's so far. I will get out to the garage tomorrow and try out the suggestions that were mentioned.

My gut feeling is a bad pilot bearing/bushing. It just seems like ,to try and explain it ,when you are using a air grinder to ream out a hole and it starts to bounce around the inside of the hole, type of vibration. I am not sure how else to explain it.

I have thought about the vibration and I remember that there was one before I did the work. Not as bad , but it was there.

Yeah , I am sure the mount is exaggerating the issue, but there is something else wrong and I have to find out what it is.

Would a worn out tranny do this? I have no records on this tranny. Other than the tag says it is out of a 1983 Mustang SVO, so I can assume it has seen it fair share of abuse over the years. Would a rebuild help?

Would I be better off finding a World Class transmission, rather than rebuilding? $200 on a rebuild kit or $200 to $400 for a used World Class tranny plus rebuild. A couple hundred more but is the World Class that better of a transmission?

Sorry to be long winded, but a detailed question "usually" gets a detailed answer.

Thanks for listening

Jeff

 
check the yoke going into the tail shaft. A lot of times the tail shaft bushing is worn and not replaced. The seal usually gets replaced, but not the bushing. See if you can get any up and down play in the yoke while seated in place in the tail shaft housing.

 
Is the vibration in high gear on the road? Does the vibration come and go? Is there a similar vibration wirh the clutch engaged in neutral... disengaged? Is the vibration present in all gears at the same RPM?

The more you can describe the vibration the easier it will be to narrow down the cause. I am looking forward to see what the issue is.

 
Is the vibration in high gear on the road? Does the vibration come and go? Is there a similar vibration wirh the clutch engaged in neutral... disengaged? Is the vibration present in all gears at the same RPM?

The more you can describe the vibration the easier it will be to narrow down the cause. I am looking forward to see what the issue is.
It happens all the time. Clutch out, have not tried it engaged. I have only ran it in first and second, too bad of a vibration to try any more than that. Same RPM( although that is a guess, I don't have a tach yet.) And even in neutral. When I stand next to the motor and rev it, I don't notice it as much, but sitting in the seat it is obvious.

I will look at the yoke, It still has the stock drive shaft, and I read somewhere the t5 is long than the auto by 3/4 of an inch. I wonder if it is binding?

Thanks for listening

Jeff

 
If the T-5 is from a SVO Mustang(84-86) the gear ratios are way off for use behind a V-8 (4.03:1 in first gear, I think). A world class T5 with a 2.95:1 first gear is a better choice and will handle more torque. Chuck

 
The u joint bolts are tight, pull the drive shaft.

Pull the shifter boot, handle, lever, speedo cable, all tight.

Loosen the tranny mount, put jack under bell housing, remove cross member and take bolts out between tranny and bell housing( all tight).

Lower trans to floor, look in through hole all the way to the pilot bushing. Didn't look bad, but some dust and debris from the clutch.

Pulled bell housing and clutch , and took a digital caliper to the pilot bushing, then to the input shaft of trans..

.020 difference. Seems ok,but I don't know the specs on this.

Re install bell housing, and starter , block up back of motor under the housing, and start engine.

Yup vibration is still there. Although a lot less that before. Hooked up my timing light which has a tach feature and it shows up around 2300 rpm.

Tomorrow I think I will pull the flywheel and try running it again.

Any thoughts?

Thanks for listening

Jeff

PS I put new rubber motor mounts in two weeks ago. So no polyurethane feel.

 
Found this article interesting:

http://www.fordmuscle.com/archives/2005/12/T5Rebuild/

I thought there were actually some tidbits of useful information:

Ford began using the Borg-Warner designed T5 in small passenger cars in the early 80's. However these early non-World class (NWC) models weren't suited to handle the power of modified V8 engines, and it wasn't until the availability of the World-Class (WC) T5 gearboxes designed for the new fuel injected 5.0L Mustangs that the popularity of the transmission took off. Compared to NWC T5's the WC's benefit from needle bearings under the gears and tapered roller countershaft bearings for reduced friction. This change also allows the later to run considerable less viscous ATF fluid rather than heavy gear oil. The blocking rings are upgraded from brass to fiber lined steel for smoother gear synchronization. The early WC T5 versions were rated to handle 265 lb-ft of torque, while subsequent changes to gear material and size in 1990 bumped the torque rating to 300 lb-ft. The 1993 Cobra T5 was rated to handle 310 lb-ft, while Ford Racing's aftermarket "T5-Z" could handle 335 lb-ft as a result of a smaller first gear (2.95:1 compared to 3.35:1) and stronger steel.


To be clear, this is 2300 RPM without the rear wheels spinning?

 
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I'm thinking you have just described an unbalanced flywheel. See if a weght has come off.
X2 what flywheel did you use? Early engines have a 28 ounce imbalance. Later model engines like the 5.0 have a 50 ounce imbalance in the flywheel. This will cause a NASTY vibration like you describe.

 
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