Transmission/clutch Chatter

1972_911T · 02-13-2006, 08:29 AM

I have an early 915 gearbox when driving the other day I noticed a sort of chattering noise that only seems to be present when the car is moving with the clutch pressed. I first noticed it pulling out of my drive in reverse when I dipped the clutch but now im noticing it in all gears when pressing the clutch to change. The noise sound a bit like when you try to set of when you havent quite got it in gear properly and the gears clatter a bit not particually grinding its fainter. The nise seems to come from inbetween the rear seating area at the front of the trans. Anyone have any ideas what it may be? Also the gearbox as just been rebuilt by a transmission shop to have the input shaft bearings replaced, he told me everything in my box is good and he couldnt recommend any aditional work.

Thanks Steve

Grady Clay · 02-13-2006, 10:08 AM

Steve,

Let’s have some more information.

I assume from your post this didn’t exist prior to the transmission work.

Is the clatter/vibration with road speed or engine speed or other?

As you take off from a stop and slip the clutch, does it judder?

Is it more pronounced accelerating or trailing throttle?

Is it temperature dependent?

Does it shift properly?

Is it different in the various gears?

Exactly what was done in the transmission?

Was the clutch changed?

Are all the fasteners (engine mount, transmission mount, CV joints, etc.) tight?

Have you had it back to the mechanic?

Sorry for the lengthy questionnaire but this is solvable with good communication.

Best,
Grady

1972_911T · 02-13-2006, 11:37 AM

Hi Grady

Gearbox was striped inspected inputshaft bearing changed along with seals then rebult. Everything I belive is tight but will chk CV joints etc tmrw as im aware there prone to losening. The noise is only noticable when costing with clutch pressed inbetween gear changes. No the noise didnt exist before rebuid.

Oh and no clutch judder when releasing clutch and no noticable virbration along with the noise.

Thanks Steve

MBEngineering · 02-13-2006, 01:26 PM

HI it sounds like the 5th/rev selector is addjusted wrong or the trani is hitting the body, check the gearbox moutingif that is ok run the car up the road if the noise has gon' in 5th the selector is wrong!!!! if so box back to the builder????
if you would like to ring me about the noise please do so , mike at MBEngineering 01539567959.

regards mike

1972_911T · 02-14-2006, 03:29 AM

Hi Thanks for the responce took the car out this morning before I had read your post the noise is more of a ratlle like something is lose in the gearbox. Contry to what I said before the noise is not just when the clutch is pressed its when in gear as well but more noticable when clutch is pressed it seems more linked to road speed than engine speed and only when the selectors is in 1 2 3 R positions I dont recall hearing it in 4th or 5th. or when changing to these gears.

Does that shed any more light on what it could be? What I mainly want to acertain is if im going to damge anything by driving it as I intend to do an engine drop in 1000 miles to adjust my valves re-tourqe my heads and fit a new clutch as the engine has had a rebuild. So if possible I would profer to drop the box then and take it back to the shop. Obviously if this is somthing that will cause damge then it will have to go back to the box shop and hopefully I can convince them that they should be responsible for dropping the box and sorting out the issue.

Thanks Steve

MBEngineering · 02-14-2006, 07:29 AM

HI if the noise has go'n in 4/5th gear then the selector is addjusted wrong and rev' gear is slightly engaged, a 1000 miles should wear it off and TRASH the box, please ring me 015395 67959 uk land line 07885622051 uk mobil.

regards mike

Grady Clay · 02-14-2006, 08:45 AM

Steve,

I’m going to take a scary approach. If there is this noise in 1-2-3 & R but not 4 & 5 that could mean the free gears in 4 & 5 are noisy when free and not when engaged. I suppose that could happen if the lock nut on the pinion were loose, although I world expect the noise to possibly go away in 3rd also. If the pinion were loose, I would expect there to be a noticeable difference accelerating and trailing throttle.

That said, a lot of noises “disappear” in 4th or 5th because they are masked by road noise from tires and wind.

I would have some local experts with good ears listen to the noise.

I would drain the oil and inspect the magnet. Removing the shift pivot plate for inspection is worthwhile.

If you find there isn’t risk of destruction, some extended driving might be appropriate. Depending on where in Yorkshire you live, it is around 150 Km to Kendal (sorta Denver to Cheyenne.) You have a volunteer with Mike.

I hope it turns out to be simple.

Best,
Grady