Transmission clunk

[plc]

Hi Guys,

Gearbox came off today and in all gears there is approx 15-20 degrees movement in the input shaft before the output shaft moves. Really noticeable when I put an old clutch plate on to test it.

Dropped in the gearbox and swing arm to the repairer but I feel the gearbox must be the fault now. Going to get the shaft inspected while off anyway.

Best to all,
Paul

[nhmaf]

Finger crossed for you that the repair comes in under $400.

 

[plc]

Hi All,

I received the call today from the BMW workshop. Cush drive in the gearbox is damaged and needs replacing. Shaft cush drive is fine (thank goodness). Thankfully bearings in the box look quite new and must have been replaced relatively recently.  Labour and parts are going to be a little under $1,000.  Ouch. Thank goodness I pulled the gearbox off myself. Next time I will bite the bullet and disassemble the box too.

It proves what I have suspected my bike knows when I have money. Whenever I get a financial win my bike decides to have something replaced. Who says machines aren't self aware!

Best to all,
Paul

[nhmaf]

I'm glad that your mechanic has gotten to the root of the problem, but I am also sorry that it turned out to be the most expensive possibility of the ones I envisioned.  Well, at least you'll have a gearbox good for another 100K miles after this servicing!

Yes, vehicles do have some sort of sense or knack of sucking up the money when it comes available.    I had been setting aside some money to buy a nice /6 airhead this month, and wouldn't you know it, last month my truck died and needed serious repair.   Suddenly $1600 of the $2500 I had saved up toward the airhead disappeared.... grumble grumble..

[oldbiker]

Hi Paul

It seems I have had the same problem with a clunk in gearbox while accelerating or slowing in 1st or 2nd gear. I checked for all the usual culprits ,oils etc,loose tranny bolts and the universal joint. I got advice to check Wiki on this site and it is superb. I have never had a BMW so I was on a learning curve. To pull off the flange entailed buying 4 bolts with the same thread, drilling 4 holes in a piece of 8mm flat plate to match the flange, a larger hole in the centre to accommodate a hefty bolt with its nut centred  and welded.A steady bench and vise is needed. but it will come off with a delightful bang.
When I opened the gearbox I found no problems with the gear clusters. Nhmaf suggested that it could be the cush spring on the input shaft. I have replaced the spur gear, spring and drive lobe along with bearings and seals. I followed the advice on Bjorgs page in Wiki and it was wonderful. I have the pages and picture s printed and displayed in my workshop.I also replaced the nylon roller on the selector with a bearing as suggested. I just finished assembling the 83 LS65 today and could not wait to take it for a run even though we are witnessing the worst flooding here for hundreds of years. Anyway I braved the rain and went for a 20 mile spin and the joy to the change from an awful "clunk" to a satisfactory "thonk". All the gears change smoothly and I really enjoyed accelerating through 1st and 2nd and slowing down. When I had the old spring out and compared to the new one the dimensions appeared the same but the tension must have been somewhat weaker. I imagine you may have the same problem as me if you cannot find a problem anywhere else.
PS I also checked the cush spring in the drive shaft even though I Knew the sound was coming from the box.
Hope all works out for you. Get stuck in as R65 is a pleasure to work on.

Cheers

Oldbiker

[plc]

Well guys,

I picked up the gearbox on Xmas eve and will put it in soon. Apparently the mechanic said it was the most worn cush drive he had seen in a gearbox.

But when I got it to the workshop at my school, I noticed the gearbox still has some free play between input and output shaft, i.e. in gear the input shaft moves around 10 degrees before the output shaft moves. Now this gearbox is freshly reassembled with a new cush drive, shimmed , new seals and bearing are all good. So I want to just clarify, do they all do that?

Best to all,
Paul