Wear on splines of output shaft of a gearbox

rapandi · Oct 17, 2019

Hi Team

I am new to this forum. I need some advice.

I have a problem that needs solving but I don't think, this is one which can be solved as a DIY.

For a while now I have been working on a project at home. I have been restoring my 1972 BMW 2002 tii. I have been working on it for a few years now. I am not too far from completing it.

There is one part of this project that I have been putting off for a while now and that is the gearbox. I have a 5 speed gear box in the car. It works fine but after 47 years in service it has some niggling issues like leaking seals etc. I can fix most of these problems. However there is one thing that is concerning me and that is as follows.

The output shaft on the gearbox has splines on it (14 splines). There is a metal output flange with corresponding splines that sits on this output shaft and gets torqued down in place. Then the propeller shaft connects to this 4 hole output flange and propeller shaft connects to the differential at the back of the car. The interface between the output flange and the output shaft is my concern.

I have noticed that there is a bit of backlash between the flange and the output shaft (see video in link below). I inspected the splines on the output shaft and the splines on the flange. They both appear to have some wear. I don't think it’s supposed to be an interference fit between the two but certainly is not supposed to have so much play.

Dropbox - Video 15-10-19, 6 02 43 pm.mov - Simplify your life 15-10-19%2C 6 02 43 pm.mov?dl=0

Dropbox - Video 15-10-19, 6 03 24 pm.mov - Simplify your life 15-10-19%2C 6 03 24 pm.mov?dl=0

I have been contemplating for a while now as to how I should fix this. Since the gearbox is 47 years old BMW no longer make the output shafts nor is it possible for me to source a used or brand new out put flange. So that rules out replacement parts.

I could source another gearbox from another model car similar to mine but my chances are very slime. 5 speed boxes are almost impossible to find after all these decades and even if I did find one, it most likely would have suffered similar wear and tear after being in service for several decades. So not worth going down that track.

I could bolt it all back together (with Loctite) and keep using it but it will one day be an issue where the splines will get destroyed totally.

Also this gearbox is very valuable just the way it is. So it would be nice to restore it.

My question - Is there any way I can rebuild the splines on both the output flange and output shaft such that they fit well in to each other? Is spray welding an option? Can it be built up by having it plated in some metal compound etc? I know this is potentially an expensive and time consuming road I am heading down but I am seeking different options before I make any decisions. If you have any ideas then please do share.

If I were to strip the gearbox down can I take the output shaft and the output flange to a competent machine shop who could build the splines up and rectify the problem?

I am looking for any suggestions so that I can make an informed decision.

Any help is much appreciated.

Regards

Raj

janvanruth · Oct 17, 2019

it sure looks like a lot of wear
i do not know from experience about welding up and cutting new splinesbut i guess it shoud be possible.
however on a musso, at one time sold in australia as a mercedes benz, the driveshaft splines are coated in some kind of plastic to take out the play.
if one takes off the plastic the shaft has play not unlike yours.
so maybe there would be a way to cover the splines with a plastic coating?

HuFlungDung · Oct 17, 2019

This is not an application for a spray weld. That is only for a sleeve-like buildup on a shaft surface, usually for use under a bearing or a seal.

The thing about arc welding is that the resultant deposit will be soft (hence machinable). The part would have to be sent out for carburizing to put a hard case back on. Still, if you're not going to put a lot more miles on this thing, then a soft deposit that is a GOOD fit will probably be fine for a long time.

Making the companion flange is not a big deal. There may be jobber parts out there that can be adapted to this situation. Maybe even a slight alteration of the tooth number or diameter of the spline might allow a jobber flange to work. I know some guys want the part to look original. That's fine, I'm not the restorative genius, I like to get done what needs doing to make a machine work.

PackardV8 · Oct 18, 2019

Anyone think building up via plating might work? Haven't done it on a BMW transmission but it's worked on similar applications.

jack vines

PocoLoco · Oct 18, 2019

Ive had worn hydraulic cylinder rods chromed up by .040" on the diameter and ground back to size, so its possible, imho, to repair by plating. Finding a shop to do it is another matter. Chromeing will add material more or less evenly, to the worn and unworn areas, so some machining will probably be needed afterwards. Also chrome does not deposit much in the id of holes without special fixtures to place an electrode in the bore. Ive had success with green locktite on worn shafts like this, maybe give that a try first. Clean everything good with brake cleaner, spread green locktite on the splines and assemble. Let it cure overnight. And make sure the nut holds the flange tight, not just tight on the shaft threads. The wear pattern looks like the flange was loose enough to move a little with the shock loading common in manual transmissions. Good luck with it.

thermite · Oct 18, 2019

rapandi said:
Hi Team

I am new to this forum. I need some advice.

I have a problem that needs solving but I don't think, this is one which can be solved as a DIY.

For a while now I have been working on a project at home. I have been restoring my 1972 BMW 2002 tii. I have been working on it for a few years now. I am not too far from completing it.

There is one part of this project that I have been putting off for a while now and that is the gearbox. I have a 5 speed gear box in the car. It works fine but after 47 years in service it has some niggling issues like leaking seals etc. I can fix most of these problems. However there is one thing that is concerning me and that is as follows.

The output shaft on the gearbox has splines on it (14 splines). There is a metal output flange with corresponding splines that sits on this output shaft and gets torqued down in place. Then the propeller shaft connects to this 4 hole output flange and propeller shaft connects to the differential at the back of the car. The interface between the output flange and the output shaft is my concern.

I have noticed that there is a bit of backlash between the flange and the output shaft (see video in link below). I inspected the splines on the output shaft and the splines on the flange. They both appear to have some wear. I don't think itâ€™s supposed to be an interference fit between the two but certainly is not supposed to have so much play.

Dropbox - Video 15-10-19, 6 02 43 pm.mov - Simplify your life 15-10-19%2C 6 02 43 pm.mov?dl=0

Dropbox - Video 15-10-19, 6 03 24 pm.mov - Simplify your life 15-10-19%2C 6 03 24 pm.mov?dl=0

I have been contemplating for a while now as to how I should fix this. Since the gearbox is 47 years old BMW no longer make the output shafts nor is it possible for me to source a used or brand new out put flange. So that rules out replacement parts.

I could source another gearbox from another model car similar to mine but my chances are very slime. 5 speed boxes are almost impossible to find after all these decades and even if I did find one, it most likely would have suffered similar wear and tear after being in service for several decades. So not worth going down that track.

I could bolt it all back together (with Loctite) and keep using it but it will one day be an issue where the splines will get destroyed totally.

Also this gearbox is very valuable just the way it is. So it would be nice to restore it.

My question - Is there any way I can rebuild the splines on both the output flange and output shaft such that they fit well in to each other? Is spray welding an option? Can it be built up by having it plated in some metal compound etc? I know this is potentially an expensive and time consuming road I am heading down but I am seeking different options before I make any decisions. If you have any ideas then please do share.

If I were to strip the gearbox down can I take the output shaft and the output flange to a competent machine shop who could build the splines up and rectify the problem?

I am looking for any suggestions so that I can make an informed decision.

Any help is much appreciated.

Regards

Raj

View attachment 267439 View attachment 267440 View attachment 267441 View attachment 267442 View attachment 267443

BMW didn't "make" that gearbox. They bought it. From Getrag, if my 3100689 (a 1971 1/2 EG: Zenith carburetted, not FI as the 'true" 1972 MY ones were, 3.0 4dr) is any guide.

Getrag actually ship a higher unit-count of transmissions than better-advertised ZF. Also steering units (your 3-series used a Getrag for that too - just as mine did) and other geary stuff.

Not all Getrags go into German vehicles. Not all even go into passenger cars.

"Manual" gearboxes tend to stay in service with fewer alterations for FAR longer years than automatics do. There is simply less to f**k with, and less to gain on 6, 8, 10 speeds as to fuel economy once you get a decent 5-Speed design into production.

I'd not jump to the conclusion that a replacement part is as hard to find as you think. It is indifferent, for example, to the selection of ratios, one gear to the next, which DID change, one application to another.

Just look in more places by gearbox model rather than the chassis it lives in. First thing you find are PLENTY of conversions. Check parts-bin on that part alone for commonality or possible improvement.

Could be that you find a used one with less wear off the back of some other Pilgrim replacing that silly Guibo resilient coupling BEFORE it started deteriorating rather than after.

BMW shudda stuck to motorbikes, actually. They controlled more of the components.

Their early motorcars were largely parts-bin exercises. Same brakes, seats, window actuator suppliers, electricals, yadda yadda as Mercedes and rather a lot of the components directly interchangeable as well. Funny thing as-of the 1970's? Mercedes Dealer Service parts-counter prices were often lower than BMW, same item!

jim rozen · Oct 19, 2019

There's some wear there yes. It's far from being a drop-dead failure. You have two options here.

1) do nothing, put it back together and put moly anti-sieze in there.

2) purchase a new output shaft and a new coupling. Dismantle the gearbox and replace
the worn parts. Good used parts another option here.

3) don't bother fooling around trying to get the worn parts repaired. The cost in terms of time
and money will swamp purchasing new if available.

As an aside, BMW motorbike gearboxes have spline couplings also. The clutch inner rides on
on the input shaft via a spline. On the older bikes this is quite coarse, the newer ones (airheads)
are finer and do have wear issues.

The driveshaft on most of these couples to the bevel drive with a sliding coarse spline. This is
typically immersed in 90 wt oil and hardly ever shows wear.

The wheels on some of these are coupled to the bevel drive with a spline. The female and
male spline do wear and this is a noticeable issue on high miles bikes. This is repaired by
replacing the female spline and often the male spline (actually part of the ring gear, $$$$) can
be built up with braze and then recut. This extends the life somewhat.

If you can buy new parts, do so now. Keep them on hand for later. Expect to pay upwards
of $1K for the parts.

dsergison · Oct 21, 2019

Please hear this out. It will sound pretty "weird, cheap, farmer, ghetto, etc..." but I have successfully repaired similar splines and they have never gotten loose again.

I packed the clearance with flattened sections of steel wire. I flattened out tig filler wire (70k psi yield) until I could just barely insert it into the space on the slack side of each tooth. (I chose to put the wire on the side of tooth not normally loaded) Then I hammered the wires in in an alternating pattern like tightening lug nuts. Then I used some locktite to keep them there.

It took some test fitting with different thicknesses / widths of filler wire but it was fairly easy to do.

Peter Colman · Oct 21, 2019

I would not give up on finding parts, I would look at European car dismantlers and BMW dealers. If this fails, you could take the shaft out of the box and you will find that the outside diameter of the splines is the same as the bearing bore so building up is problematic. You could try having the existing splines ground to clean them up and then make either a sleeve to fit inside the existing output flange or a complete flange with the splines spark eroded to suit, I would be reluctant to try building up the internal spline in the flange as it is hard to get even distribution down holes with either metal deposition or plating.
Another way of dealing with the internal splines is to make a simple push broach which you grind to size as you do the shaft splines, this will then be used to cut the inside of the bush in the flange.

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Wear on splines of output shaft of a gearbox

rapandi

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janvanruth

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HuFlungDung

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PackardV8

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PocoLoco

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thermite

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