915 gearbox whine and box removal

Gary71 · Post by **Gary71** » Wed Jan 05, 2005 8:05 am

My 2.4 '72 with a 5 speed 915 has always had a loud whine from the gearbox, which is particularly loud in third. Now I've fixed wheel bearings, exhaust and driveshafts this is the loudest noise source in the car.

It's very much a whine rather than a bearing rumble and I'm suspecting it's the final drive. Does anyone have any similar noises and how have they been fixed? As the volume changes depending on gear selected my first thought is that the pinion bearing is worn allowing the pinion and crown to misalign to a greater or lesser extent. Whilst the engine is out I want to take a l look. I'm tempted to go in and change all bearings and the second and third gear syncros, but would like to think that the noise might go at the same time, I'd be gutted if I rebuilt it and it still wailed at me!

Also the Haynes describes using spacers to release pressure on the release bearing prior to removing the box, but the factory manual just says undo the bolts and take it off. Does anyone have experience of removing an early 915 box?

Thanks for any advice

impmad2000 · Post by **impmad2000** » Wed Jan 05, 2005 9:29 am

Gary,

Sorry, can't give any clues to the whine, but...

I took my 5 sp 915 to pieces last year. I bought the alignment plate and the deep socket to clear the speedo drive. I am sure I can arrange a loan for a fellow DDK member.

When I looked at my box, I thought about replacing the bearings as a matter of course. I was lucky, my bearings were in excellent condition, the costs would have been crippling, so I just re-used the originals ! The inside of a 915 is not so scary that I wouldn't strip it down again if needed
anyway.

Cheers

Luke · Post by **Luke** » Wed Jan 05, 2005 9:35 am

mine whines in 5th a bit, I like it though, it sounds like a supercharger!

something's worn in there but it's not on a high priority list of things to do

Gary71 · Post by **Gary71** » Wed Jan 05, 2005 11:34 am

Many thanks for the offer for the tools, I'll take you up on that.

Did you strip it to replace synchros, or just to have a look! Hopefully the anticipation of a stripdown is more scary than the reality

With the bearings I'm interested how you evaluated condition by appearance. Unless the bearing is about to die completely they always look fine to me. I've replaced rumbling wheel bearings in the past and stripped the old part to find... nothing

.

Luke, Indeed the whine has some charming qualities, particularly when pressing on...

My concern is my previously relaxed attitude to box failure has been adjusted by a friend whose Saab 9000's 'slight bearing noise' turned into 'locked front front wheels and sliding to a stop by the side of the M1...'

When we stripped the box we found the bearing for first gear had melted and welded itself onto the output shaft, so when he engaged third as he came down the slip road the whole lot siezed with lots of teeth and bits of metal everywhere... Could be fun in a 911

impmad2000 · Post by **impmad2000** » Wed Jan 05, 2005 12:18 pm

My strip down and rebuild was as a result of it jumping out of 5th.
It turned out to be caused when a plonker replaced the clutch, kippered the thread holding the release fork pivot. They fixed the problem by re-drilling the pivot thread Glueing the pivot in place ! It leaked some oil out to a level just too low to lubricate properly !
I consider myself very lucky in that there was next to no damage caused to most of the gearbox. The only wear I could find was as a result of my holding the car in 5th (New selector fork and slider only). The jumping was fixed by re-tightening the nut that holds the gears onto the shaft, held by a tab washer, but only finger tight.... I had an insert machined to repair the clutch fork pivot.
When I studied the gear box for wear, I became apparent that I have a good gearbox. All the parts looked like the "After repair" photos I found. All the synchro rings and dogs were barely worn at all. The bearings too seemed fine. I reset the selectors and re assembled .
Can you believe my shock when the first time out , it jumper out of 5th ! I was mortified. To my relief, however, it "bedded in" it has been fine ever since. It has even taken track day abuse !
The '69 clutch layout in my car operates the "otherway around" and so I didn't need to compress the clutch on mine, sorry, can't guide you on that part...

Bob_Salmon · Post by **Bob_Salmon** » Wed Jan 05, 2005 1:53 pm

Gary71 wrote:
Also the Haynes describes using spacers to release pressure on the release bearing prior to removing the box, but the factory manual just says undo the bolts and take it off. Does anyone have experience of removing an early 915 box?

Thanks for any advice

I asked Crispin Manners about this before I removed my box - quoting the Porter/Morgan 911 restoration manual. He just smiled and said "Forget it, just wriggle the fork around and it will come off". It did!

Bob

Gary71 · Post by **Gary71** » Wed Jan 05, 2005 2:27 pm

Thanks Bob. Wiggling it sounds much easier than messing around with spacers.

Gary71 · Post by **Gary71** » Mon Jan 10, 2005 1:28 pm

Pulled the lump out on Saturday night, so I'm ready to commence the stripdown

. Looking at the thing on the garage floor you can just see a hundred projects in front of you. Self control (normally dictated by wallet anyway) will have to be strong not to do stuff 'just whilst it's out'.

It only took 2 1/2 hours to get out anyway, and that included sacrificing my 3 year old son's play table to make a trolley!

Hopefully I determine the source of the whining when it's in pieces.

Tim, I've sent you a pm about the tools, thanks.

Luke · Post by **Luke** » Mon Jan 10, 2005 1:38 pm

now's a good time to give the engine a good steam clean, repaint/powdercoat the engine tin, engine mounts and cross bar too

Peter · Post by **Peter** » Mon Jan 10, 2005 2:19 pm

My three year old son whines a lot and it would certainly get worse if I took away his play table. Are you sure you're not making your problem worse

impmad2000 · Post by **impmad2000** » Mon Jan 10, 2005 3:16 pm

Sorry Gary71, I have got myself confused. I have 901 gearbox tools. I have PM'd yer back.
I hope you haven't taken it all apart based on my tools !

sorry !

Gary71 · Post by **Gary71** » Mon Jan 10, 2005 4:57 pm

Spotted my plan exactly there Luke, the garage that did my MOT does powder coating so all the metalwork will be off soon. The relatively small cost of this has to be worth it versus me spending hours cleaning all up and making a poor job of painting it.

Peter, Maybe that's what the whining noise was in the first place.....

Nope he loves the 911 and giving up his table (which I made him anyway!) is a small price to pay to get to go out in 'Daddies car', last time we went out we broke down (throttle link). Hopefully after this rebuild it will hold together a bit better.

Tim. No problem, pm'ed you back again.

Gary71 · Post by **Gary71** » Wed Jan 19, 2005 1:15 pm

I've found the whine, nothing to do with the final drive, just third gear being worn. The surface finish has started to go on one of the pair

All the synchros have already being turned around (at least once!) so that has blown my cheapskate gearshift fix...Also the third gear slider dog teeth are totally rounded off.

impmad2000 was quite right, it comes apart very easily, if only I can work out how to secure the input shaft whilst undoing the 41mm nut (I have a BIG spanner...) I've read the 'greatest thread ever' on Pelican but it doesn't seem to offer any great clues.

No need to undo the shift forks as the Haynes manual suggests, so hopefully it should go back together without needing complex fixtures.

Dyno Soar · Post by **Dyno Soar** » Thu Jan 20, 2005 7:49 pm

Wow Gary I am impressed with anyone prepared to pull their drive train and rebuild it.

Good stuff.. have you done this before?

Gary71 · Post by **Gary71** » Fri Jan 21, 2005 7:53 am

Nope this is the first gearbox...Plenty of engines and stuff, but I've never braved gearbox internals before. But it really isn't that bad!

I've got the big nut off now, holding 5th gear VERY tightly in soft jaws on the vice did the job. Felt a bit ugly at the time but has done the job without damage.

I've tracked down a 23/29 third gear pair in the US from an 83 box, so this will hopefully cure the noise.

Just got to commit to spending £500 on all the bits now! ...then do my spring plate bushes, crank oil seal, repair some rot in the engine bay, paint everything and put it all back together...

This could take a while...

DDK - Die Deutschen Klassiker

915 gearbox whine and box removal

915 gearbox whine and box removal

Re: 915 gearbox whine and box removal