Shake Your Rear-End...Please

[1550vt]

Hey...you folks out there with an "early" Lehman belt drive kit do me a favor...if you get time. I have around 30K on my Ultra Lehman conversion and just happened to sit on my right fender the other day and heard a "clunk". As I would sit down and get up..it would "clunk". I traced the noise to the differential housing while I had the 105-pound wife jump up-n-down on the fender. I had recently had a wheel bearing failure and got all that fixed, but now fear I had the inner bearing get damaged when the outer ran loose for a while. But, nothing seems to be loose, the belt runs true and neither wheel appears to have any abnormal side-to-side slack. I think the noise is coming from "inside" the differential carrier and it may very well be that the grease has slung out, or I have been using the wrong grease. These older units call for a shot of grease at 1,000 mile-or-so intervals and I can't say I have been judicious about keeping to that schedule...but I do grease it now and then.

I think it's just a little slack in the rear end. If you would jack-up the right hand side (long side of the axle) and rotate (bump) the tire left and right...you can determine how much slack you have and what-if-any noise you hear. I would like to hear from somebody that could do this. A new differential has a price-tag of $2,585 to the dealer and some of you know what all is involved in changing that out.

I just need a "feel" for how much slack you have in your differential and would appreciate any help you could give me.

Mine pulls fine and nothing is loose....may just be normal slack and my use of improper grease?

[Mr.Wizard]

If I had slack in my rear end I wouldn't be announcing it on the internet... Just say'n dude...

[1550vt]

I can always depend on my good buddies to come through with a complete and detailed explanation of any problem.

Now....got your butt out there in the shop, throw a jack under the shock-mount on the right hand side....get that right rear wheel up, and rotate (bounce) it clockwise and then counter clockwise and tell me how much slack you have.
I suffered through your rattle with the connector in your trunk thingy....now you gotta' help me with this. I do not want to be stranded in Milford, Utah again....unless I can find that mechanic at the Chevron service station named Aron Cox.

[Mr.Wizard]

Yes Dad

It's already up in the air so hold your horses. I don't have a Lehman but I do know where you can upgrade..

[Mr.Wizard]

Like I said, she was already up in the air.

I took both tires and shook them, turned them and grabbed them for a good jerk back and forth.. No clunk or side to side motion, nothing up and down either... Grabbed a brick and used a crow bar like checking for bad ball joints too.. nothing. But I have a maintenance free Motor Trike.

She's tighter than Burt Reynolds Toupee.

[1550vt]

Good answer there Wizard and you did not even use any mathematical formulas, or exotic theory in you description either.

I was bored stiff (and the clang was really buggin' me), so I went on out and ripped out the rear end and tore-down the differential. The innards looked fine..plenty of grease and the drive and spider gears are in real good shape. Nothing broken or out-of-whack.

I don't know how your "maintenance free" drive line is put together, but the ones I know about have the outer wheel bearing and then an inner bearing pressed onto the differential case. The outer bearings hold the axle and the inners hold the differential in place via a tight fit within the axle tube. The only thing I found that might remotely be causing the problem is a little slack in the inner bearing on the RH side, which was the same side on which the outer failed out there in Milford. Now that I know nothing is crazy inside the differential, I can sleep at night and if the new inner bearings don't fix my "clank"...well...I will just not be sitting on the RH fender anymore so I won't hear it. I do think there is some normal component wear here also. There is a fuzz of slop in the drive gear/axle splines. What can I say....they are Ford parts.

Hey....call me after 31,000 miles on yours and tell me if your "maintenance free" kit it has any slack in it. At least my fenders don't shake...ha....ha....ha!

[Mr.Wizard]

Oh yeah... I forgot to tell you VT. I found the fender shake. Before I had the Ultra converted I had a TrueTrac on the frame. I removed it and the fender shake went away.

The trunk rattle was lack of quality control from my builder.

The Motor Trike differential is maintenance free but I doubt the axle bearings are. It has a three year warranty on it so I won't be pulling any axles just yet.

[Gorilla]

Dave I still have my true trac on also. Did you notice any other changes when you removed it other than no fender shake?

[1550vt]

Dave...I can't blame anything on my builder....my builder was me!

Yep...I think the later model diff's are sealed and oil-filled, but the early models took grease. The diff has a grease fitting on it that requires a little every few thousand miles (1,000 per the manual) and I thought it was a possibility that I had let that interval slip and ran dry for a while. This little bugger is about the size of a quart fruit jar, but you got to tear the whole a!! end out of it and part the housing just to get to it. While I am in there, I will go ahead and replace those old cleave blocks in the swing arm with the delcron bushings, which should take the "mush" out of the cornering. And....replace the drive belt.

My summer is shot on this project. Old men like me can only work in 30-minute stretches....I figure I'll be through sometime in September!

[Mr.Wizard]

Dave I still have my true trac on also. Did you notice any other changes when you removed it other than no fender shake?

Ted, there were no other changes in handling at all. Skuuter and I had a little bit of fun while in Maggie. He saw me from behind and could tell you if there was body sway or twisting but you couldn't feel it from the riders seat, just the asphalt patches.

All seems normal now with the exception of the missing phantom fender rattle.

[Mr.Wizard]

Dave...I can't blame anything on my builder....my builder was me!

Yep...I think the later model diff's are sealed and oil-filled, but the early models took grease. The diff has a grease fitting on it that requires a little every few thousand miles (1,000 per the manual) and I thought it was a possibility that I had let that interval slip and ran dry for a while. This little bugger is about the size of a quart fruit jar, but you got to tear the whole a!! end out of it and part the housing just to get to it. While I am in there, I will go ahead and replace those old cleave blocks in the swing arm with the delcron bushings, which should take the "mush" out of the cornering. And....replace the drive belt.

My summer is shot on this project. Old men like me can only work in 30-minute stretches....I figure I'll be through sometime in September!

Beer's the answer my friend... keeps ya young and working except for the potty breaks.

[Gorilla]

Thanks Dave

[1550vt]

Back to my "clunk". Let this be a heads-up just in case you ever really have an outer axle bearing failure. My outer bearing failure saga is in another thread out there someplace, but I will mention this here.

Bottom line...if you have an outer bearing failure and run it for very long before you really can tell....just go ahead and get prepared to change you inner bearing also. Mine likely would have run on for goodness knows how long, but when I sat on the right fender and heard that "clunk"....I just had to dig into it and find it. My inner bearing (the one that holds the differential in place in the axle tube) had some pretty serious slack and I attribute that to the wobble in the axle when the outer bearing went. I just bit-the-bullet, tore-down the differential to check the drive and spider gears and then replaced all the other inner and outer axle bearings. Now....my clunk is GONE!

My wife is still around, but the "clunk" has disappeared.