can it be ujoint?
 

I get a pretty good vibration on the down hill, will a worn ujoint cause it?

Re: can it be ujoint?
 

Very doubtful it is the u joint. Very likely it is the pinion nuts have come loose and the pinion is moving forward in the center section of the rear end. Here is why I know that. When you are on the throttle, the pinion pushes into the ring gear. When you are NOT on the throttle, if the pinion nuts are loose, the ring gear will push the pinion forward, causing the vibration. Sorry to be the bearer of bad news. We have fixed several of these this last year, and all had the same downhill vibration.

Steve @ Berts Model A Center

Re: can it be ujoint?
 

Thanks, Steve, So does that mean the nuts will need to be tightened or there will also be damage? And I know once it is apart I will check everything.

Re: can it be ujoint?
 

Wow, that means that the pinion race is sliding in the neck of the banjo OR the pinion and the driveshaft are "squishing" sideways away from the ring gear.

Re: can it be ujoint?
 

Yes, you want to fix it as soon as possible or you will be buying a new ring and pinion, if not already.

Re: can it be ujoint?
 

a bad ujoint will viberate when coasting, wont when under power

Re: can it be ujoint?
 

To endorse WestCoast's statement above... Does the vibration cease when you disengage by pressing the clutch or selecting neutral and start freewheeling downhill?

Re: can it be ujoint?
 

Because of the bearings supporting both sides of the driveshaft at the U joint area, I'd put my money on the pinion bearings being loose. The roller bearing at the front of the driveshaft and the rear tranny bearing should give the driveshaft good support to keep it from much vibration, unlike an open driveshaft with no support other than the U joint.

Either way, the rear end should be removed and the problem corrected right away.

Re: can it be ujoint?
 

I may be a tad dense but, I didn't get the implication of what it meant if the vibration ceased in neutral or with the clutch disengaged? Did it mean the U-joint is the culprit and the differential is OK - or what? I haven't tried that yet so I don't know what to expect. My gut feeling would be that either unit could be affected by removing the engine drag.

Re: can it be ujoint?
 

OK - I just went for a short drive and made several long downhill runs. With the clutch disengaged the vibration goes away. Is it the U-joint or the differential?

Re: can it be ujoint?
 

Tom is suggesting you go thru the differential. This would also include pulling the u joint. There is a good tutorial that tom Endy wrote on the orange county model a ford club website.
You should take the advice offered and plan on addressing the problem before it gets worse IMHO.

Re: can it be ujoint?
 

We could do a poll, but either way the rear end needs to be removed. I'm still putting my money on loose pinion bearings. Steve mentioned he just did one with the same symptoms and I've also done one with the same symptoms and both were loose bearings.

Just get to it........we're anxious to find out!:D

Re: can it be ujoint?
 

as mentioned no one here has a Crystal ball it could be the u-joint , diff or even something else like an engine or trans issue....
feel better:eek:

Re: can it be ujoint?
 

Are you sure it's just not a normal decel vibration....? or is it actually a grinding/vibration type noise from the drivetrain. Loose pinion bearings aren't that hard to detect... and the U-joint if really bad will be there all the time... The Driveshaft/pinion bearing noise will change when power is applied vs/coasting.

I would determine if it's a normal thing from engine decel vs other drivetrain issues. If your new to Model A's I might suggest having someone schooled in your area ride or drive to check it out with you.
Larry Shepard

Re: can it be ujoint?
 

I don't recall this much vibration from the last '30 Tudor I had here in Maine and indeed, I did have a well-known classics restorer take it for a spin. His comment afterward was to just "drive and enjoy it - it doesn't need anything!" Still, the vibration is annoying and it needs to be checked out further. For the record, the vibration is fairly "heavy," but without any "grinding" noise like you mentioned. It's more like the sensation from an out-of-balance or bent shaft, predominately felt through the steering wheel.

Re: can it be ujoint?
 

What happened to the original poster, Tim? I thought he was asking the question?

Re: can it be ujoint?
 

I was wondering the same thing???

Re: can it be ujoint?
 

Tim here, Got the rearend all apart, Not seeing anything obvious. No lose bearings or bad gears. Will keep looking.

Re: can it be ujoint?
 

That was fast Tim! I'll be anxious to hear what you find.

Re: can it be ujoint?
 

I honestly think that the judgement was quick to condem the rear axle when it could be an engine that has some heavy vibration on decel. That can be from bad engine mounts, connecting rod weight imbalance ...etc . While you have try rear end apart examine the front driveshaft bearing and removeable sleeve and the driveshaft itself . Look for wear on the driveshaft. With the rear end out remove the u joint and test for tightness and any slop .

I once had purchased a "restored" coupe for resale from an estate . Beautiful restored car but had a terrible vibration. The ultimate culprit at the end was the torque tube and driveshaft. Yes, the torque tube must have had some rough treatment in life
Never in all my time had I seen one like that .
When done was smooth as silk
Larry Shepard