Spitfire Spitfire rear end noise from heck

[rockman]

I can't be the only one with this problem.74 spit no overdrive 37K original miles. Noise is a steady thump at 5mph a thump every second this increases with speed Noise in every gear at any speed it's periodicity increases with speed. Noise is diminished when accelerating let off the gas and starts whacking away, it is more evident when turning mostly left turn. noise with brake on or off. Help Mr Wizard Thanks Rockman

 

[Dale]

I'm sure someone will jump in that knows something, but my first guess would be a tire problem. Maybe a tread seperation thing. These cars tend to suffer age related tire problems long before tread wear out. Sorry I can't be more helpful than that.

 

[DNK]

Tire wouldn't be stress related.

 

[Bob Claffie]

U-joint on the axle. Bob

 

[booley]

U-joint on the axle. Bob

that would be my guess, because it changes when on and off the gas, and in turns

 

[DrEntropy]

Go with Bob's theory. Matter of fact, all the axle joints need a good inspection. IIRC, the left side is the first place to look. But it's been a while.

 

[Moseso]

Could be the U-joint on the drive shaft too. As I read the top of this thread, that was the first thing that popped into my head, "U-joint." Of course, as the owner of a solid rear-axle car, it never occurred to me to think axle joint, which it might be -- but the drive shaft has u-joints that clunk like that too...

 

[skucera]

Rockman, that is the exact noise my car made when I needed to replace the rear axle U-joints. There is no ambiguity. Nothing else on a Spitfire makes that sound.

Scott

 

[71MKIV]

As a 25 year owner of a Spitfire, I concur, I had the same "thunk" under the same circumstances, rear axle u joint had given up the ghost, er bearings.

Get the back of the car supported and look over everything that moves back there. The u joints might hide their distress, but you can tell if you start waggling things around.

 

[guzzul]

As all have suggested, U-Js are likely. Definitely check the propshaft, not just the axles. I would also check the nuts and bolts that hold the u-joint mounting flanges to the diff. If they have come loose you can have the same effect.

I would get to it soon. You do NOT want these coming apart at speed.

 

[DrEntropy]

I would get to it soon. You do NOT want these coming apart at speed.

On the bright side: that'll only happen ONCE.

 

[Andrew Mace]

As all have suggested, U-Js are likely. Definitely check the propshaft, not just the axles....

That makes sense, although bad u-joints on the propshaft, in my experience, tend more to set up a constant vibration on power, or overrun, or sometimes both, depending on which u-joint is bad. Oh, and if your '74 has the strap-drive propshaft, also make sure the straps are intact (or, for that matter, present, as I recently encountered such a shaft where someone had removed the straps and poorly bolted the yoke back onto the shaft -- NOT a good solution).

I would get to it soon. You do NOT want these coming apart at speed.

For sure. Been there, done that! I couldn't believe how difficult it was to push my old '74 across my lawn and driveway after the tow truck dropped it...until I realized that the flailing axle shaft had beaten the snot out of the handbrake cable guide, locking down the brake on that side completely!

 

[71MKIV]

That reminds me,

I had one of those strap type prop shaft in my car. Apparently there is some sort of bushing in the thing to keep it centered where the straps are, and that bushing had gone away. It would be fine up to about 40 and then suddenly start vibrating.

I fixed it by replacing it with an early spline type shaft.

 

[Norton47]

There's this information also.
https://www.canleyclassics.com/infodatabase.asp?article=noises

I emailed Canley to find out what the "pin" was they referred to in the propshaft section on the strap drive. This was the answer:
Strap joint always goes towards the diff end.

The pin is hidden in the centre of the strap end of the prop and its the part that allows the small amount of plunge within the range of bend of the straps themselves.

Regards

This must be the bushing you refer to.

 

[71MKIV]

Yea, I think that must be it, If I got ambitious, I could go look, it's stil in my attic.

It seemed to me to be a half arsed way of making a flexible joint.

and according to Canley, mine was in backwards too, as the joint was in the front.

oh well.

Moot point now anyway, as I am putting in an o/d, which takes a whole different driveshaft anyway. See my other thread.