Clutch knocking noise

[zigzagsky]

Apologies for a delay in my replies but I have had some family issues to deal with.

I tried your idea Hugo to knock her into neutral when driving her and the knocking noise is then related to engine speed and not road speed.

So I guess this means that it’s on the input side of the gearbox.

When I get the chance to spend some more time on investigation, I will do as Pat suggests and take the top cover off. I’ll leave draining the oil and looking at the plug until I start the removal process.

Brian

[Hugo]

Might pay you to keep the old oil in case you want to send a sample for analysis. Of course if you find that you have a tooth missing that probably won't be necessary ;)

[Durango2k]

... that find then is an home-made analysis, anyway :-)

Carsten

[Hugo]

Any progress on this puzzle? I was thinking about it again this morning, and I thought how unlikely it must be that anything you have done has damaged anything in the mainshaft/output shaft area.
Going out on a limb again, I don't suppose it is possible that what you have done is simply torn an engine mounting and now have the engine (cabs or something) knocking on the frame?
I think you said the knock slows when the speed drops, so that would seem to rule this out. It is in any case improbable, but no more improbable than any other theories so far advanced.
At present the most likely outcome I can see is that you will end up with the engine on the ground and a pile of gearbox bits all over somebody's garage floor, while being none the wiser but much out of pocket.
I'm sure if it were mine I'd just keep driving it till somethng goes bang. Then at least you'll know what it was ;)

[zigzagsky]

I’ve checked to see if it was something like a loose engine mount or something external but it seems to be internal.

Due to work and domestic pressure I have not been able to do much but I hope to get a look inside the gearbox through the inspection cover next week just to see if there is anything obvious.

The current plan is that a fellow E Type owner is coming over on the first weekend of December to help me take the drivetrain out and then I have been recommended a company to repair and refurb the gearbox.

I will naturally keep you posted Hugo (and everybody else who has helped) as I’m sure you are keen to hear what it was eventually.

[Hugo]

December huh? Don't know if I can stand the suspense that long! What bugs me is that what appears to be the only possible source of this noise seems so implausible as to be verging on the impossible. Yes, I know Sherlock Holmes' dictum about such matters, but I fear that in this instance it may not be so elementary.
I found myself in a similar position years ago when I was young and foolish, and undertook to rebuild a Ford V6 engine with a mysterious knocking noise for a customer. I got away with it, and the noise was cured, but to this day I don't know what caused it.
If this were my car (note I am not telling you what to do) I would be very reluctant to start stripping things down for 'repair and refurb', until I was pretty confident what I was looking for.
Again, if it were mine, I'd be tempted to keep driving until something went 'bang'. Then at least you'd know what to repair! But I like living dangerously!
Anyway, best of luck with it.

[zigzagsky]

For those following this thread I thought I should give you an update...

Just prior to Christmas I managed to drop out the engine and gearbox with the physical assistance of a good friend who also has an E Type and the technical assistance of Pat.

Unfortunately family commitments over the festive period followed by a severe bout of man flu delayed the splitting of gearbox from engine until last weekend. Yesterday I took the gearbox to Ken at Klassic Transmissions near Wolverhampton. He lifted the lid and thinks it’s a broken lay shaft gear. He will strip it down over the coming week and send me photos of the broken bits so should have some pictures to post soon.

The good news is it’s fixable and I now have the opportunity to do all the little under bonnet jobs that would be nigh on impossible with the engine in place.

[Hugo]

Broken layshaft gear, huh? Does he mean a broken tooth? That is something I suggested, but qualified my remarks by saying how unlikely this was. You don't normally knock a tooth off a constant mesh gear unless something drops in there, in which case the mating mainshaft gear has probably had it also.
Anyway it sounds like you're getting there!

[phil.dobson@mac.com]

your in excellent hands with Ken. apart from his knowledge and supply of quality pats he doesn't charge the earth unlike most of the others these days. I would be keen to hear how it all works out.
best regards
Phil D

[zigzagsky]

Ken’s initial thoughts are indeed a broken tooth as you suggested Hugo. I guess I will know for sure later in the week when he gets it apart.

[angelw]

Brian Wrote

Ken’s initial thoughts are indeed a broken tooth as you suggested Hugo. I guess I will know for sure later in the week when he gets it apart.

Hello Brian,
If broken tooth it would be the First Motion/Lays-shaft cluster, or Lay-shaft Cluster/ Reverse Idler Gear combinations.
Having read your Thread, its clear that the evidence points to the Lay-shaft cluster and the gears that are in constant mesh with it.

The constant mesh gears are the First Motion Shaft/Lay-shaft cluster and the Lay-shaft/Reverse Idler combinations.

I have a client’s gearbox currently in work for what I suspect is an identical knocking noise as your gearbox. The symptoms are identical to yours and wishful thinking was the First Motion Shaft bearing being the cause. But the Reverse Idler gear is a common source of rhythmic knocking noise.

We have a rig, including a clutch, whereby the gearbox can be test run at any stage of assembly and the First Motion Shaft bearing was immediately eliminated. Because the Reverse Idler is often the cause of such noise, the Lay-shaft cluster and Reverse Idler was reinstated and the assembly run. With the Reverse Idler in the Forward Gear/Neutral position (Picture 1 below) the knock was quite evident. Sliding the Reverse Idler to the Reverse Gear engagement position (Picture 2 below) extinguished the noise. On inspection, there was reasonable wear on the section of the Reverse Idler Gear that is engaged with the Lay-shaft cluster when in the forward position, its position most of the time. However, the wear was quite even with no particular tooth damage that would suggest being the cause.

Picture 1
Picture 2 A late series Reverse Idler Gear (Picture 3) was put into place and the assembly run; no noise in any Reverse Idler Gear position. The late series Idler Gear is the same as the earlier version except for the groove machined midway along the gear tooth. The only use of the groove that I can think of is that the faces on each side of the groove my act as oil slingers. The groove has no affect on the general function of the Gear.

Picture 3
With a bit of luck, the issue with your Gearbox may also be the Reverse Idler Gear. This is easily replaced once the Main Shaft and Gear assembly is removed and would be about the cheapest fault to rectify compared to teeth on the Lay-shaft cluster, or First Motion Shaft damage.

Regards,

Bill

[Hugo]

That's interesting. So the reverse idler is spinning all the time on these boxes? That strikes me as an odd arrangement. The difficulty I have with your theory is that the noise in this case appeared quite suddenly, although wasn't it after Mr Zigzagski used the starter motor to wind the car backwards? But the starter can't put more load on the gears than the engine, can it.
Good old Morris Minors - the early gearboxes anyway - were forever knocking a tooth off first/reverse gear. But both gears on those boxes are sliding spur, not constant mesh.
I think we've got it cornered now though - can't wait to hear the final analysis.

[angelw]

All the gears are spinning (free wheeling) all of the time when not engaged and with the clutch engaged. Disregarding the Lay-shaft cluster gears, the Reverse Idler spins the 2nd quickest at approximately 100 revs per 1000 engine revs less than third gear (which spins the quickest).

Fourth Gear is effectively the gear on the First Motion Shaft that constantly drives the Lay-shaft cluster. I say effectively as its the synchro Hub engaging the First Motion Shaft that equates to forth gear.

First Gear and the Reverse Idler are simultaneous driven by the same gear on the Lay-shaft cluster. Brian, moved the car using the starter motor and first gear, so there is a chance that First Gear, or the driving gear for First Gear on the Lay-shaft cluster may have been damaged. As the clutch wasn't used, the result of using the starter motor would have been tantamount to aggressively dropping the clutch, but with a whole lot less power being applied. I just don't see that being the cause. But if it was, then it would be likely to have happened in the near future just driving the car.

The noise described is quite commonly traced to the Reverse Idler Gear. We come across it a lot; hence the reason for having a spare Reverse Idler to hand. Although the noise in the Gearbox pictured in my previous Post seems to be caused by wear on the Reverse Idler, it also started very abruptly. One day the Gearbox was reasonably quite, the next there was a rhythmic knock. I see this quite frequently with CNC machines, where noise in bearings and gears can start quite suddenly. Clearly, there can come a time with worn parts that they can suddenly become noisy.

Regards,

Bill

[Hugo]

That is most interesting, if surprising. I would not have expected that to happen.

[zigzagsky]

So a quick update.

Ken was struck down with 'Man Flu' so has been quite poorly I imagine as I also had 'Man Flu' just after Xmas and was VERY poorly!!

He did not find any obviously broken teeth etc. but did find that both the first and reverse gear idlers were quite damaged as well as the layshaft so will be replacing these together with bearings etc.

Up until I read the info posted by Bill, I was a little worried as I had a nasty feeling that Hugo, you were right - remove engine & gearbox, take it all apart and not find the cause!!

So it hopefully looks like it is the same problem (and result) as outlined very comprehensively by Bill and that by replacing the parts, all will be well.

Brian