No, James, I don't think its that. I made a recording of the tap and sent it to Phil at Road and Race. He seems certain it's not the diff, thinks it more likely to be one of the compensation springs/plungers in the drive shafts.
To be fair, he's probably right. Before I stripped all out it was making this noise as well as others from the diff. The diff has had just about all new parts but for the CW and P and the frequency of this noise (2/ wheel rev) doesn't fit with them. He also says that they showed no damage.
So, got a pal coming round to pinpoint the location of the noise while I rotate the wheels then I'll do one shaft at a time, and strip them right down. They seemed fine on the bench before but maybe not.
Anyone got a supplier of the springs/plungers, boot clips etc?
PS The diff is quieter than it was, the chattering on overrun has gone and the car also behaves itself better coming out of corners accelerating away in lower gears. The fishtailing has stopped now it just seems to be a nice progressive drift, if the tyres lose traction.
Redline and CC do a boot and clip replacements for the tripoid joints, including pouches of the very specific grease thats for tripoids, haven't found a source of the springs or plungers, which I presume are GKN bits.
The irony is I have a sierra diff with Titan lsd, just been fully rebuilt, along with new UJs in the propshaft, and I too have a tic tic tic....that wasn't there before...
I thought it was the outer CV on the nearside driveshaft, I dismantled it, cleaned it, regreased it, found nothing, replaced and tic tic tic...annoying isn't it !
Oh yes, it's annoying! I wouldn't mind a tic tic! Mine is a deeper tapping sound.
After the car had run, I jacked it and span the wheels; the tapping was quite clear. Now that it's cooled, it's much less noticeable but it's still there. I'm wondering if this points to a driveshaft, the sound being clearer when it's hot and the grease thins a bit but masked by the grease when cold. Then again, if it's this fabled spring, it's probably not much lubricated by the grease anyway!
The wonders of 60s' engineering!!
If I knew how I'd upload the sound file!
Exactly the same symptoms, louder after a 20 mile run when things are warmer, my spring and plunger cap are ok, on the end of the driveshaft i thought it was, I was also thinking of removing the caliper, and spinning the wheel, just to make sure it's not caliper/pad related.
Good idea. I will do that this time. But I do know what pad rattle sounds like and this doesn't sound like that but you never know.
Just a thought as the discs/pads expand and contract, and at least it eliminates a possible source.
I shall check. The other thing it sounds like 2 knocks per wheel rev, I can't imagine anything on the disc assembly that would do that.
Loose brake pad catching as the run out of the disc passes through?
Well, after completely dismantling the rear end for a second time and taking the diff back to Phil, it appears there was a small mark, or something on the pinion, causing the tapping sound. Phil was very apologetic, they've never seen it before, but he stripped and rebuilt the diff whilst I went down the road for an hour to get a sandwich.
So, all back together again. On my own refitting the diff this time but I knocked up a simple wooden jig to support the diff level and square on the 3 flat surfaces on its base. Cable tied that to the jack, put diff on, raised on jack and slid straight into position, no problem.
The tapping has gone. Only issue is that it's still got the chatter that it's always had from new, the only difference is what where before it did it when you eased gently off the throttle, now it does it when you lift off altogether, which is harder to work around. Hopefully, I'll get used to it. No noise under power or when braking, just on overrun, when the engine braking slows the car.
Buy proper diffs. Titan is - not the best. There is a reason the pre-load spring is breaking down...