915 rebuilt trans buzzing in 1st & 2nd..

targa44 · 03-07-2013, 05:08 PM

...my shifter has a fairly loud zzzzzzzzzzzzzzzzzzzzzzzz buzzing while the car is moving and stops when I stop. I can feel the shifter rod at the link behind the seats and it's coming from the trans.

any suggestions?

thanks,

tobluforu · tobluforu's Garage

Does it go away when the clutch is in, what about at idle?

Peter Zimmermann · 03-07-2013, 05:26 PM

Driving the car with the cover over the coupler removed can produce a lot of different noises that you don't notice with the cover and carpet in place. Put the cover on and drive the car again, tell us what it's like.

jlex · jlex's Garage

Sounds like you need a new shift rod bushing. Metal against metal is causing that buzzing sound.

targa44 · 03-07-2013, 08:14 PM

If it's not raining tomorrow, I'll go out again and get more variables thrown in... clutch in - out... speeds, etc.

Peter - I've got the 'vented' cover plate, but the sound transmission is manifested in the shifter itself. I can just feel the vibration at the coupler with the cover off.

My mechanic said I should upgrade to the 'adjustable' 915 shifter - with the adjuster nut towards the front (which I've bought) and maybe I can just make the shifter stop making the buzzing sound.

However, my concern is for the vibration that's causing the buzzing. It just doesn't seem like I should be getting a (I'll call it a high freq.) vibration.

thanks,

Peter Zimmermann · 03-08-2013, 07:10 AM

That's a bizarre symptom. No vibration prior to the trans being worked on? Is the repaired trans original to the car, or an exchange?

I guess that it's possible that something was damaged during R&I (linkage, eng/trans mounts, shift coupler?), or maybe something was left loose during re-installation. Has your mechanic put the car back up on a lift, and double checked the engine/trans mounts, and if the engine to trans is properly tight? Was the clutch replaced also?

Do you get the feeling that your mechanic wants to help, or wants you to go away?

T77911S · 03-08-2013, 07:20 AM

does it change with speed

how about coasting with the clutch in

does it do it in all gears. any gear worse than others

jack the car up and spin the wheels.

targa44 · 03-08-2013, 07:57 AM

... I'm not completely familiar with the components history. I bought it as a "roller" and had what it came with rebuilt. I'd asked my mech. to 'check the transmission' for soundness and the next thing I knew is he'd sent it to Havasu and said he doesn't do transmissions. It was a huge bill (included new ring and pinion $$$).. etc.

In putting it back together, we installed a new clutch disc and throwout? bearing. The sound has developed after 2000? miles since that install and is getting louder. I'll check for the potential connections / fasteners / mounts soon.

I appreciate all the comments from everyone - good, solid suggestions... I'll plug away from my end.

thank you,

zippy_gg · zippy_gg's Garage

Can you drain the transmission and check for metal particles or chunks?
Since the tranny was just rebuilt you will likely find some fuzz, but chunks would be bad news.
Remove the plate at the bottom and check the 3 nuts on it for tightness.
If the gear oil is clean you can re-use it.

Peter Zimmermann · 08:44 AM

Quote:

Originally Posted by targa44

... I'm not completely familiar with the components history. I bought it as a "roller" and had what it came with rebuilt. I'd asked my mech. to 'check the transmission' for soundness and the next thing I knew is he'd sent it to Havasu and said he doesn't do transmissions. It was a huge bill (included new ring and pinion $$$).. etc.

In putting it back together, we installed a new clutch disc and throwout? bearing. The sound has developed after 2000? miles since that install and is getting louder. I'll check for the potential connections / fasteners / mounts soon.

I appreciate all the comments from everyone - good, solid suggestions... I'll plug away from my end.

thank you,

It does sound like something external is coming loose, but if all the fasteners are proper and tight (you need an expert's help for this - lot's of variables regarding hardware used to assemble a "roller"), I think that the next step is to have your mechanic drain the trans oil and check for debris. Internal vibration from a 915 is almost unheard of, so you might get lucky and find a loose trans mount bolt, maybe a missing shift rod bushing in the center tunnel, etc.

Matt Monson · 03-08-2013, 08:54 AM

Quote:

Originally Posted by targa44

the next thing I knew is he'd sent it to Havasu and said he doesn't do transmissions. It was a huge bill (included new ring and pinion $$$).. etc.

Just so that you are aware, Havasu is California Motorsports. They are not in the habit of installing parts that are not needed and generally do excellent gearbox work. I'm not saying that they are perfect and you could have an issue with the rebuild, but I just want you to understand that your mechanic sent it to one of the better 915 builders in the country.

That said, I would hope that your mechanic passed the repair quote by you for approval before allowing CMS to proceed with the work once they had it apart. If he didn't, I might be looking for another mechanic who communicates better.

Regards,

Matt

targa44 · 03-08-2013, 09:59 AM

Matt - yes, I was aware.. but, I'm not as ignorant as I was starting out. I didn't mention names - intending not to disparage, but it may have come across that way. Yes, CMS has a fine reputation.

thanks,

AC78 · 03-08-2013, 01:19 PM

I have a similar sounding symptom in third gear - a slight buzzing, vibration - but when I apply slight pressure to the gear shift the sound disappears. I've just installed a new coupler between the front seats and will be making a minor tweak to it as I suspect there's a very slight metal on metal contact somewhere. You might want to experiment with a similar adjustment.