output shaft runout

enjenjo · July 25, 2011, 08:22:00 PM

We are chasing a vibration on a 90 Mustang 5.0. So far we have pulled the rear end out, and gone through it, new driveshaft including yokes, and now we have pulled the trans and clutch. The vibration starts about 50 mph, and gets worse the faster you go. It does not change of you throw it into neutral and let the engine idle.

The trans is torn apart, I expected to find a bent or twisted output shaft. I found no twist, and the total runout on the output shaft is .020". I did find a shakey output shaft bushing. I will replace the bushing. Do you think .020" is too much runout? Anything else to look for?

Crosley.In.AZ · July 25, 2011, 08:31:10 PM

Quote from: "enjenjo"Do you think .020" is too much runout?

Anything else to look for?

nope , i do not see .020 as too much.

seems you have covered the stuff I would suggest to look at.

Bruce Dorsi · July 26, 2011, 12:56:23 AM

Any chance it could be in a rear wheel or tire?

chimp koose · July 26, 2011, 01:14:18 AM

Crosley is the trans expert and I may well be wrong but I would think .020 runout is a lot..I would think .002 runout would be ok but .020 is greater than the tailshaft bushing clearance and would cause problems,no?

enjenjo · July 26, 2011, 01:35:12 AM

Quote from: "Bruce Dorsi"Any chance it could be in a rear wheel or tire?

Changed them, no difference.

Warpspeed · July 26, 2011, 01:36:06 AM

Put it up on stands without any wheels or tires on it.
Run it up to 50 Mph+ and see what happens.
Try it again without the tailshaft.

No idea what it might be, but a few tests might narrow it down.
If something is shaking real bad under there, you might be able to see it.

If you have access to a roller dyno, you could also run it up to speed (at no load), and again maybe see what gets the shakes.

enjenjo · July 26, 2011, 01:41:32 AM

Quote from: "chimp koose"Crosley is the trans expert and I may well be wrong but I would think .020 runout is a lot..I would think .002 runout would be ok but .020 is greater than the tailshaft bushing clearance and would cause problems,no?

I am inclined to agree with you, but checking several manual transmissions I have here, I found over .020" movement in all of them. The only reference I could find to output shaft runout, says .5mm, which figures out to just over .019". I guess I am looking for someone with experence with this combination.

chimp koose · July 26, 2011, 03:00:31 AM

See! Crosley IS the trans expert! Gotta love this site ,I learn stuff all the time.

chimp koose · July 26, 2011, 03:04:06 AM

Just a thought but could the pinion angle be really out of whack?

enjenjo · July 26, 2011, 09:41:09 AM

Quote from: "chimp koose"Just a thought but could the pinion angle be really out of whack?

That was checked when we had the rear end out.

GPster · July 26, 2011, 11:19:56 AM

Just a strange thought. Could ther be something in the driveshaft? You know it's straight but does it always stop with the same side up if it's rolled across the floor? You'd probably need the universal joints off but if you get to that state again try it. When they balance a driveshaft they may not spin it that fast. GPster

wayne petty · July 26, 2011, 11:50:34 AM

i have fixed several drive shaft vibration problems by changing the output shaft bushing... i did not measure the play.. but there was some... the driveshaft vibration vanished after the bushing and seal change...

these were on E4OD transmissions...

i also had one... that ate up the slip yoke... like a C clip axle shaft.. a deep groove was worn into the sliding surface ... on a T5 turbo coupe... i think i still have that transmission..

the last thing... mustangs and Tbirds with T5s.. usually have a big inertia ring on the drive shaft.. i looked around last night and could not find an image of the exact part on your model...

i looked it up at the ford parts site accessed through motorcraft.com

T5s also have 3 holes along the bottom of the tail housing.. for a big weight... to dampen the harmonics... is there any sign that there were bolts through the 3 holes?? signs that brackets were bolted down tight on both sides... people throw those away... ford did not put them there for no reason..

kb426 · July 26, 2011, 01:04:44 PM

From hanging around a mustang forum some, I know that you aren't the first to have a problem. If you haven't checked the engine mounts, you should. That can cause alot of problems. I had a slightly bent driveshaft on my 32 which caused a vibe and caused the real seal on the 3550 to leak. As you might imagine, it ruined the rear bushing. I ended up removing the trans, standing it on end and then removing the tail housing. I made a driver to remove the bushing and then heated, cooled, and pressed the new one in. With a new driveshaft, life is better.

Crosley.In.AZ · July 26, 2011, 09:45:30 PM

trying to get .002 run out in a output shaft of a trans is near impossible.

i aint an expert, I just know what I see that works or not. IF this shaft has a ''wave type twist'' in it at .020 run out, then you can have troubles.

Rustangs can have body - chassis trouble as mentioned, I figure Frank has looked at the torque boxes or what ever they call them for rust, loose, popped welds that can lead to problems

enjenjo · August 01, 2011, 08:51:28 PM

We are still chasing the vibration. It's still there.

We bought another T5, went through it, and installed it with a new clutch. While we were at it, checked to see we had the right flywheel. Checked the motor and trans mounts, they are new urethane mounts. Slotted the trans mount holes to get it lined up perfectly. No change.

So far we have gone through the rear end, new driveshaft, new Ujoints, new trans, new clutch, changed the rear tires, and checked all the angles. Very little rust on this car, it came from NC. I am at a loss where to look next. The vibration changes with road speed, but not engine RPM, and is the same when under load or coasting. Starts about 65 mph, and gets worse as you go faster.