can it be ujoint?

[tim54889]

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

[SteveB31]

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

[tim54889]

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.

[100IH]

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.

[Tom Wesenberg]

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

[WestCoast]

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

[johnbuckley]

Originally Posted by tim54889

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

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

[Tom Wesenberg]

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.

[Cracker39]

Originally Posted by johnbuckley

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

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.

[Cracker39]

Originally Posted by Cracker39

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.

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?

[Brentwood Bob]

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.

[Tom Wesenberg]

Originally Posted by Cracker39

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?

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!

[Mitch//pa]

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

[larrys40]

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

[Cracker39]

Originally Posted by larrys40

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

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.

[zzlegend]

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

[Cracker39]

Originally Posted by zzlegend

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

I was wondering the same thing???

[tim54889]

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

[Cracker39]

Originally Posted by tim54889

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

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

[larrys40]

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