Drive line vibration

Dave C · Post by **Dave C** » Tue May 03, 2016 2:42 pm

A short while ago I mentioned I had a very bad vibration(drive line?) at approx 45-50 mph. on my '65 123E

I took the d/shaft to Pat's drive line and they determined it was bent.

They cut the ends off and replaced the tube and balanced it. The u-joints were also replaced.

I took the diff out as it was a bit clunky and took it to IWE Rear Ends Only and Ian replaced all the bearings and the diff carrier as a bearing had spun on it.

Put it all back together today and the vibration is still there, although not quite the same intensity. I ran it up to speed (with the axle stands under the springs to simulate the weight on the wheels) with the wheels off...no difference and with the brake drums off...no difference.

I have a new gearbox mount coming as the one on the car is a bit soft and oil soaked, but prying on the mount produces very little movement.

I can also detect no play in the front d/shaft slip joint/gearbox main shaft. With the car sitting on the ground the diff looks to be parallel with the ground.

This is getting frustrating as I have never had this level of vibration in any car I have owned or worked on. As it stands now the car is basically undriveable over 45 mph.

Cheers,
Dave.

Post by **peteleo** » Tue May 03, 2016 4:25 pm

Dave,

Doesn't seem the vibration is coming from the drive-train anymore.
Are the tires balanced ? Have you checked the motor mounts ? There should be 1/2" gap between the vertical section ( mounts to the cross member ) and
square section ( mounts to the block ). It is common on these type of mounts that the rubber collapses and metal sections will touch causing engine vibration. I can send a photo of a new mount if needed.

Pete

zephyrgary · Post by **zephyrgary** » Tue May 03, 2016 4:37 pm

Had a similar problem with my Minor convertible once. The tires were ancient and had become very hard and wooden. Swapped them out; problem solved. Bear in mind, they looked fine and had good tread, they were just too old.
Gary

Dave C · Post by **Dave C** » Tue May 03, 2016 5:17 pm

The tires are new. I can run up the engine with gearbox in neutral, no vibration.
Run it up in gear with the back wheels and brake drums off...vibration. All U-bolts tight etc.

I think I'll take the d/shaft back to Pat's and have them re-check it.

I was wondering if the axle half shafts were bent, but they were so easy to re-install after I put the diff back in makes me think they're ok and the rear axle housing also.

Got me baffled at this point. The vibration is bad enough that the rear view mirror disappears into a blur

Cheers,
Dave.

Edit.

Pete.
The motor mounts look new. Good clearance between the parts.
The tires are balanced.

Post by **peteleo** » Tue May 03, 2016 6:08 pm

Axles can bend if the rim got knocked against the curb. You will see the axle flange wobble. I would wait until you install a new trans mount.

mark · Post by **mark** » Wed May 04, 2016 5:38 am

make sure the U joints are in line with each other...I have seen a reputable drive line shop get these out of alignment with inexperienced help.

Dave C · Post by **Dave C** » Thu May 12, 2016 8:59 pm

After doing everything I can think of the find this vibration...car is basically undriveable at 50mph.... I noticed that there appears to be what I would call lowering blocks, about 1" thick between the axle mount and the rear springs.

Is this standard fitment for this car? I have a new trans mount coming from the UK and will fit that before I try anything with these blocks.
Does anyone have a photo of the standard 105E rear axle mounts.

The p/shaft has been rebuilt (new tube) by Pat's Driveline, the diff repaired (spun carrier brgs) by Ian Wood at IWE. The rest of the car is stock engine, trans, all x-members under the car look unmolested.

The two main causes of d/line vibes are d/shaft and pinion angle.

I'm pulling out what little hair I have remaining.

Cheers,
Dave.

Post by **peteleo** » Thu May 12, 2016 11:07 pm

BTW has the front end been lowered too ?
My 105E has 1" block spacers and also lowered 1" in the front. Normally that will not cause vibrations at high speed. Pete

Brett Wilkie · Post by **Brett Wilkie** » Fri May 13, 2016 2:08 am

I still think that you should get back to basics and actually measure the pinion angle/line, you might find something?
Maybe the 105e guys can tell me, is it possible to install a 105e leaf spring backwards, front eye to rear eye??

Post by **peteleo** » Fri May 13, 2016 7:47 am

Rear L/S bushings are smaller while the front L/S pressed in bushings are much larger. Also the two end bolts are different diameters. It's obvious that the leaf spring fits in only one way.

Dave C · Post by **Dave C** » Fri May 13, 2016 8:45 am

Pete.

It doesn't appear that the front is lowered. I haven't taken any measurements but eyeballing the car it does seem to be slightly lower at the back. Or it could just be old age eyesight

Cheers,
Dave.

Post by **peteleo** » Fri May 13, 2016 10:01 am

Slight variation in height should not be the cause of vibration. i.e.:
passengers or loading the trunk with 75 lbs will lower the back end approx. 2" . The drive line should compensate for heavy loads.
Is there excessive trans oil coming out the tail shaft ? Tail shaft bushing maybe the culprit along with an oil soaked trans mount.

Dave C · Post by **Dave C** » Fri May 13, 2016 10:16 am

Rear of trans is dry. There is no oil on the bottom of the car. I suspect that the rear mount is quite old and has had some oil on it in the past, that is why I am replacing it..if it ever arrives from the UK.