I raised my motor and tranny 1.5" for better ground clearance. The driveshaft is about 18" long and connects to an IRS. The yoke pulled out of the TH400 tranny about 1/2". Now when I decelerate there is a rumbling sound, which gets worse with braking. Ideas?
1. Drivetrain to body interference, since the motor and trans are raised. Possibly shifter even hitting the body when you let off the gas or hitting the brakes....
2. Motor to mount to frame bolts loose or possible trans to crossmember bolts loose.
3. Grab the yoke and try to gyrate it...and then the driveshaft. Normally, I set the driveshaft up so the yoke is 3/4 of a inch off the tailshaft. Now, if when the car was built it and that 1/2 to 3/4 rule was used, and you've now added 1/2 to it....thats 1" to 1-1/4" off the tailshaft. The further back you are, the looser the fit on the splines....this could very well be the problem.
4. Check your center section on your IRS for loose bolts or mounts.
5. A harmonic vibration either in your 1/2 shafts or in the driveshaft. Tie a Bungie cord around them, without the hooks to see if it quietens down.
I had a rumble in a Hemi Drag car, it was a Challenger R/T. I had it up on the lift I bet about 20 times. Then finally had someone up it in neutral while up on the lift, redlined it a few times, I finally heard it. Someone stuck a soda bottle up inside the frame. At a certain RPM, a harmonic vibration would make the bottle dance in the frame.
Checked for interference, etc and all looks OK. I measured and there is 1" of exposed yoke. From the end of the tranny to the u-joint centerline is 2.5". Do these numbers seem excessive? Also, this tranny and u-joint are 20 years old and I'm guessing there is some wear that could exacerbate the problem. I'm gonna go to a driveshaft shop tomorrow and want to know what to expect.
1" inch doesn't seem excessive to me... that's about what I have, and I measured for the shaft exactly the way the driveline shop told me to. If you grab the yoke and try to move it radially (up and down or sideways) on the tranny output shaft, is there any play? AFAIK, there should be no play. That would indicate worn splines or inadequate engagement of the yoke to the shaft.
Dave: Bill O'Reilly used it the other night. And the waitress at IHOP asked me if I wanted my eggs scrambled or exacerbated. But she didn't look too bright. I guess the yokes on her
1" inch doesn't seem excessive to me... that's about what I have, and I measured for the shaft exactly the way the driveline shop told me to. If you grab the yoke and try to move it radially (up and down or sideways) on the tranny output shaft, is there any play? AFAIK, there should be no play. That would indicate worn splines or inadequate engagement of the yoke to the shaft.
SS could be right....doesn't take hardly any slack there at all to get sounds and or a small vibration. Since you raised the drivetrain, how does your pinion angle look? Are all your U-joints good and tight? U-joint straps?
If you raised the motor and trans both together, ie, like putting a block between the trans and mount and motor to motormounts, not accounting for pinion angle, over 18" of driveshaft length, could possibly pose a problem....Also, while your in the vicinity, shake the pinion and see if the bearings are still tight.
If you raised the motor and trans both together, ie, like putting a block between the trans and mount and motor to motormounts, not accounting for pinion angle
Let us know your pinion angle....
My guesses would be that you either changed the U joint angle or that your yoke going into the trans is worn or the bushing is worn in the tailshaft. You could have pulled it out past the good spot and it has some slop in it now where it enters the tailshaft.
Any one of those could make the driveline obstreperous.
The U-joint angle increased when the tranny was raised. So it might be the joint or the yoke slop or the bushing. Off to the driveshaft shop and see if their highly trained grease monkeys can find the culprit. Stay tuned. Thanks, guys, for not bloviating.
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