Knock knock

[72Hardtop]

So I've got the bus back finally and it's running great. But I have a knock noise that was not there prior to the engine work haven been done. It's only heard when the bus is cold and when letting the clutch out in gear. Once the bus is at operating temp the noise is gone. It isn't loud. Example: tonight I started the bus and when I push the clutch in and put it into 1st gear and slowly let out the clutch just as the gear grabs and starts to move I can hear a subtle knock.. knock. There are no clutch noise/knocks heard when engaging/disengaging clutch in neutral. Clutch works very smoothly.

While the engine was out I had the clutch checked and pilot bearing replaced. The clutch was in good shape as was the flywheel. TO bearing was also in great shape.

I've also driven it doing some sweeping left/right turns to check the CV's and no knocking/clicking noises are heard and the boots are in great shape.

It's only heard just as the clutch engages and once the bus is at operating temp it's no longer heard.

My guess is that as the bus gets to operating temp things have expanded creating tolerance and preventing the knocking sound from being heard. I'm in the process of checking all the heater tubes and such for anything that might be loose. What may be some other items I could check such as engine/trans hangers etc...

It's definitely torque/clutch related as it only occurs when the clutch is first engaged (when engines cold). Most noticeable when engaging 1st gear due to low engine RPM. The clutch cable is a few months old (replaced using German Supply kit). Clutch is adjusted properly. Bus was not making the noise prior to dropping off at the shop for the work done.

Knock noise is not heard at operating temp. Revving the engine cold/hot does not produce any knock, thumps, bumps or banging noises of any kind.

Much appreciated.

[vdubyah73]

similar noise from my bus. i believe it's cv. only knocked a little at first, only at low speed, 1st and 2nd gear, with light to moderate throttle. goes away when grease warms up?
i determined it's a cv by listening to it and first noticing it only does it when going forward with throttle, 1st and 2nd. then over time i could get the noise on a left turn, after enough miles for for the knock to diminish. this happened over a span of several weeks. 30 miles a day, i don't use it every day in the winter. gonna wait for a free day, 60ºs and sunny. getting old, don't want chapped love handles from rollin' around under a bus.

i think we can get away with cleaning, inspecting and repacking with grease, if the balls are in good shape. then if my mental coniptions are correct you flip it and install with the wheel end on the tranny and the tranny end on the wheel. this puts the work load on another surface.

[ruckman101]

I was leaning towards CVs, too.


neal

[vdubyah73]

re-read your post. i don't think the shop had anything to do with it. the sound and conditions you reproduce it under make it sound like a subtle noise to me, you just suddenly conciously recognize the ''new'' sound that doesn't belong. that is how my own diagnosis began.

whats that noise? then it's gone. you might not hear it again that day. you could let it develop until you can tell what side the noise is on. think mine is on the right.

[72Hardtop]

Update:

I had someone move the bus gently forward while in gear with e-brake on while I laid underneath and the noise appears to be from the front trans mount. My guess is it was disturbed when the engine was dropped. Going to put it on the lift tomorrow and adjust the trans mount. Can those trans mounts be had new? If so where/whats the part number?

Thinking about it....which way would the trans rock when engaged from the engine? Trying to decide whether raising/lowering the front trans mount will resolve the issue.

[Amskeptic]

Update:

I had someone move the bus gently forward while in gear with e-brake on while I laid underneath and the noise appears to be from the front trans mount. My guess is it was disturbed when the engine was dropped. Going to put it on the lift tomorrow and adjust the trans mount. Can those trans mounts be had new? If so where/whats the part number?

Thinking about it....which way would the trans rock when engaged from the engine? Trying to decide whether raising/lowering the front trans mount will resolve the issue.

Mounts don't knock. Junk surrounding mounts might.

Check to see if there is too much movement in the mount itself. You can do this in gear engine off level surface. Under the car, rock it back and forth and look at how the engine/drivetrain absorb the torque.

The early '72-'75 bus front nose cone mount is adjustable. Two 17mm nuts vertical on transaxle itself. Remove the lower plate (also 17mm) to access. No need to support the transaxle. Need thin wrenches.

You ask which way it moves under take-up?
Forward push while in gear, pushes nose cone down. That is engine braking.
A rearward push in gear engine off, jerks nose cone up. THAT is what the engine does as it tries to propel the car.
Colin

[72Hardtop]

Thanks Colin, do you or anyone else happen to know the part number of the front trans mount. I was just curious haven not been able to track it myself. I can only make out the first three and last three digits on the mount itself while underneath.

Much appreciated

Jim

[Amskeptic]

Ooops...

Would someone with more mad-skillz than I just remove/edit my post from that OTHER thread regarding this bus and paste it into here. Please... it took me a while to round up all those p/ns that were being requested and dumb-*ss me just replied to the wrong thread...

Sorry 'bout that; carry on - nothing to see here but a 50-something older guy losing his marbles, one by one.

TIA

Us marble losers are duly celebrated in the current site logo.
52LostMarbles

(I remember the new '72s on the dealer showroom floor and crawled under them in delighted fascination. What I distinctly remember was the compliance of the entire drivetrain, you could jiggle those suckers with ease, and get yelled at all the way home for the undercoating wax all over you.

I wonder if aftermarket replacement mounts have been "matched" to some petrified example, because that compliance is nowhere to be found with the seemingly rock hard 431s. The most recent VW Audi rear engine mounts I bought for the Road Warrior did have an almost squish to them.

Be aware that the nose cone mount does very little in the way of static support, it is mostly a torque absorber. Since I did not think to file the nose cone aluminum to snug it up, I used an inner tube off a junkyard bike and some vulcanizing compound to "shim" the detached rubber back to the mount. Seemed to work for about 4 years with many an off-road tests included )

[dtrumbo]

Us marble losers are duly celebrated in the current site logo.

So THAT'S what those are!