[bradburm]

Happy Holidays to all,

First, Thank you to all who have helped in the past, this forum is invaluable.

Here's the deal,

I was driving my 73 Rallye yesterday and all of a sudden it felt like I had gotten a flat, as there was excessive vibration coming from what seemed like the right rear tire. I pulled over and found no tire issues, visually checked the drive train, tires, etc and everything looked fine.

Jumped back in and car started fine, but as soon as I got to about 5/10 miles an hour, the car started the excessive vibration almost to where it is undrivable. so I limped home and put in the garage and will tackle the unknown issue after Christmas.

Any suggestions or experience around this? Any diagnostic advice is clearly appreciated.

Thank you to all


Brad

[dave-r]

If it was OK before then it has to be something like the UJs on one or both ends of the driveshaft.

If one wheel is the cause it might have been damaged or if it had been ballanced the weights might have come off. But that would not have caused such a bad vibration at such a low speed.

Don't drive the car again until you have checked the UJs and the tailshaft of the trans.

[christer]

I have had similar problems once. In my case the wheelbolts had come loose or at least wasn´t sufficiently torqued. Because of this, the bolt holes had been enlarged. I can´t remember if there were any vibrations. It sounded like a worn bearing or something like that. I still have the damaged magwheel laying around somewhere. I have read that it is possible to fix the enlarged bolt holes if you drill an oversized hole and then press in a tube.

Well, just a suggestion....

[dave-r]

Good point Christer. But I would never attempt a wheel repair. Too dangerous.

[christer]

Good point Christer. But I would never attempt a wheel repair. Too dangerous.

Yeah, it is probably a good idea to be a little cautions if you have a lot of ponies under the hood. I still believe that this oversize/tube solution will work for a moderate streeter (but please don´t sue me if it don´t work). As always it is important to know what you are doing...

I came to think of a funny (dangerous? ) story. A friend of mine did choose to use a 8 3/4 Chrysler rear-axle in his ´66 Nova. (Good choise, eh? ) He decided to shorten the rear-axle so that 12" rims would fit in. The thing was that he didn´t shorten the axle enough causing the rubber to slightly scratch against the rear fenders. Now what to? He used Centerlines and since they are quite thick (or very thick? I don´t remember exactly) in the area between the bolt washer and the dumbrake/discbrake suface, he decided to turn this area on the Centerlines and and making the area thinner. Well, it is nothing that I would recommend but it worked out well for him. (Thank God.)

//Chris

[bradburm]

I have the car up on stands and will pull the rear tire first. although all the Mag/wheel studs seemed tight and in place.


When I tried to move the drive shaft, I found no slippage, could this still be the issue?

Any chance that something went wrong in the rear axle, although the car was shifting fine.

I will start tearing things apart after today and let you all no what I found, this is truly perplexing............

Merry Christmas, Thanks again all.


Brad

[Eddie]

Have you looked inside the rear drums?

[dave-r]

I have read that it is possible to fix the enlarged bolt holes if you drill an oversized hole and then press in a tube.

Actually. Thinking about it more. This would be OK on an alloy wheel with thick material around the holes. The tube would have to be just a tiny bit shorter (like 1mm or something) than the hole in the wheel and washers on the nuts would be vital.

[christer]

I have the car up on stands and will pull the rear tire first. although all the Mag/wheel studs seemed tight and in place.

A very easy way to know for sure is to replace the tyre with the spare tyre and take the car for a test drive. Well, what do you say about that proposal? I would do that if I were you. I don´t think you can see with your own eyes if the bolt holes have become over-seized or not.

[bradburm]

I will actually put the old mags back on the wheel I suspect is the problem.

If this fixes the problem, then you are suggesting that the bolt hole on the cragar has probably hollowed out beyond normal? These are very new wheels maybe 3 months and 500 miles, so I assume Cragar will warrant them?

I do appreciate all the help and ideas, I would be in a bind with out them.

Thanks,


Brad

[christer]

If this fixes the problem, then you are suggesting that the bolt hole on the cragar has probably hollowed out beyond normal?

That sounds like a good description.

These are very new wheels maybe 3 months and 500 miles, so I assume Cragar will warrant them?

I am not so sure about that though. I suggest that we continue step by step and first get sure about if this really is your problem or not.

[bradburm]

All,

Changed the rear tires but still had the excessive vibration.

I assume the next step would to replace the u-joints on the drive shaft? Would Year One have the U-Joints since they are right up thr road from me?

Unfortunately, I leave for Lousiana tommorrow ( Work there during the week) and wont be able to change U-Joints until next weekend.

Let me know your thoughts. As always, thanks to everyone for your help.

Brad

[christer]

I assume the next step would to replace the u-joints on the drive shaft??

If you jack up the car and secure it safely, you will be able to find out if the u-joints are worn or not. Make sure that you have the gearbox in neutral. Hold the pinion with one hand and the other hand on the drive shaft. If you twist the driveshaft firmly back and forth in all directions, it should´t feel loose or something. Also check the four tiny bolts that holds the rear u-joint to see if they are OK. Well, that is how I would do it.

Would Year One have the U-Joints since they are right up thr road from me?

Living next door to Year One? What a privilage! Congrats!

[spitfire9137]

Im sure you already know this but there shouldn't be any up, down, left or right movement from the ujoint, don't forget the up by the tranny either.

Yearone has ujoints I think, but you can most likely go to the local auto parts store and get the same exact ujoint cheaper than Yearone.


A question for the experts, were the driveshafts balanced, Ive never payed attention to mine. If so could be possible the weight came off his driveshaft?

[christer]

A question for the experts, were the driveshafts balanced, Ive never payed attention to mine. If so could be possible the weight came off his driveshaft?

Yes, I am pretty sure that there are balance weights. I doubt that them falling off could cause severe vibrations like the ones in this case.

[transman]

A couple of other areas you might want to look at are the mounts.
Check the transmission mount, and also the engine mounts. Over time, these can rot with age. Oil can get on them, and oil and mounts don't mix. Oil will cause the rubber to go soft and become spongy. I had a customer with a somewhat similar problem, and after looking at many other areas, he found the trans mount had gone soft. It was replaced and the problem was solved.
transman

[bradburm]

All,

I am hoping that with everyones help, I may have found the vibration issue. After removing the drive shaft I found the rear u joint in good working order but will replace it anyway. As I went to the front u joint, it was clearly apparent that one of the endcaps was missing and the spline on the u joint was exposed.

Anyway, I pulled both u joints and will replace and let all know if this truly solved the issue.

Whats interesting is that I fully expected the rear u joint to have an issue as opposed to the front as the vibration felt as if it was coming from the passenger side rear.

I will try the local autoparts store for new u joints and if that fails run up to Year One ( I am fortunate as they are only 10 miles away). Unfortunately, I will not be able to finish the job until next weekend.

Anything special about the new u joints that I shoudl be aware of, I assume that the endcap size is what is important.

Once again, I do appreciate everyones help

Brad

Thanks for everyones advice and I wil

[transman]

Nothing special about the ujoints Brad. Mother Mopar used a large and small ujoint in most of their products, and they used them for years. I'm sure when you go to your local auto parts store, they'll be there. The company I work for sells a limited number of u joints, and I know both of them are on the shelf. If I was at work, I'd give you the part numbers. If you have any problems getting them, email me and Monday I'll get the part numbers for you.
transman

[bradburm]

All,

New u-joints installed and drive shaft in place, vibration is gone so pretty confident this was the problem.

Again, Thanks for everyones assistance, I will be tearing into the brakes fairly shortly and assume that there is nothing special about doing a complete brake job on the car.

Thanks again for everyones help, this site is truly invaluable to me.

Brad

[Jon]

Glad to hear you solved the problem.

As for the brake job, I recently had been painting under the fenderwells and noticed the front brake hoses were old and cracking. I replaced them with local auto parts stock. 14-5/8 long for my 70. There is one in the rear just above the axle also. For some reason they don't have a part number for that one on a 70 but I heard a 71 will work. Anyone know of this?

Good insurance to replace them all as failure results in no brakes.

[dave-r]

70-72 suspension/brakes are exactly the same. Only difference is between disc and drum.

[christer]

Glad to hear you solved the problem.

I agree

Good insurance to replace them all as failure results in no brakes.

No brakes is No fun, right? But is it really that bad? Isn´t the brake system actually two independant systems? Either the front brakes or the rear brakes will still work in case of a leaking hose, right?

[christer]

There is one in the rear just above the axle also. For some reason they don't have a part number for that one on a 70 but I heard a 71 will work. Anyone know of this?

I found these part number in the 2003 Year One catalog:

´70 QRE23 $28.95
´71 NG90037 $28.95
´72-´74 FD9203 $47.95

That is all I know.

[Jon]

Christer wrote:

No brakes is No fun, right? But is it really that bad? Isn´t the brake system actually two independant systems? Either the front brakes or the rear brakes will still work in case of a leaking hose, right?

I thought the same thing driving to work this morning. I guess if the rear failed you would have most of the braking still functional. On the other hand if the fronts failed the rear tires would skid for quite a while. Have you ever done one of those emergency brake spin arounds?

A leaking hose would allow everthing to work until there is no fluid in the plunger. It would be sudden. Petal to the floor?? Don't know for sure. How does the proportioning valve fit in here?

I will check out the year one brake hoses. Thanks for the info Christer.

[dave-r]

Your best bet is to have some stainless braided hose made up to replace the stock hose. They do a better job as they make the line pressure higher.

[christer]

I guess if the rear failed you would have most of the braking still functional.

Yup, correct.

On the other hand if the fronts failed the rear tires would skid for quite a while.

Well, it all depends on how you act as a driver. As for the brake pedal you can easily remove pressure on the pedal. It is not as easy doing if you use the emergency pedal. That is you will skid if you use the emergency pedal and you will do a controlled skid (partly skid) if you use the brake pedal (with only the rear brakes functional).

A leaking hose would allow everthing to work until there is no fluid in the plunger. It would be sudden. Petal to the floor??

The dual brake system will prevent the pedal-to-the-floor-thing. You will still have either the front brakes or the rear brakes functional. If the front brakes still works, you will have something like 80% of the brakes still left. (and if only the rear brakes works only 20% of the braking force left).

(80/20 could be 90/10. I don´t know exactly.)

Well, that is how I see it.

[christer]

Your best bet is to have some stainless braided hose made up to replace the stock hose. They do a better job as they make the line pressure higher.

I think they are overrated when it comes to car applications. (I think I have heard that somewhere. I belive that is true if you don´t have track racer or something. On motorcycles they can be a good idea.)

The pressure will not be higher. The pedal will have a more sloppy feel tough. The braking force will not be as easy to control and will not be as precise.

[dave-r]

Sorry Christer. I have done this on many cars. The pedal is firmer and takes less effort to apply.

Rubber hose expands under presure (limiting the pressure to the brake pads) and makes the brake feel softer. Not something you want in particular and not something you want at all with manual brakes.

[Jon]

Just thinking again.

When bleeding the brakes have you ever been the lucky one sitting in the driver seat pumping the petel? I'm always the one under the car getting greasy. Anyway's my wife helped me out on this recent repair and the petel goes to the floor when the bleed valve is opened. So I think our ideas about partial braking from either the back or front system may be busted.

On another note: When doing a brake system air bleed the master cylinder pistion travels farther down the bore than during normal operation. If the M.C. is older the bore may be pitted or rusted down there thus the seal can be damaged. Then a couple of weeks later you notice the master cylinder leaking. These particales may also be released into the rest of the system.

In my opinion, when doing a brake job it may be best to do a complete brake system component replacement. Possibly even the ridgid steel lines ??

[christer]

Sorry Christer. I have done this on many cars. The pedal is firmer and takes less effort to apply.

Firmer? Yes, I agree!
Takes less effort to apply? I doubt it! (Just my opinion....)