The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: dogshome on January 01, 2022, 10:32:51 AM
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I have the final drive. It's a finned type. Uninspiring use of bathroom sealant on the flange and a stripped driveshaft filler tapped 9/16 UNC with a metric taper hydraulic fitting jammed into it. Splines show some wear, maybe 20% but OK. New seals fitted in the big bit by my friend, I have the seals and big torque wrench for the input side. Plus the tool he made. We put a 9/16 tap through and I've cut a suitable bolt with copper washer for the filler.
Much cleaning and slooshing with solvent and nothing unusual came out. Bit of metal dust very fine and on the magnetic plug. Normal.
The only bit that is bugging me is the very slight rust on the outer (inner race) due to it not being on the unit for a few years. Cleaned with scotchbrite, but not convinced.
Not planning to take the main cover off, although now un-decided about that too! But it looks like the input bearing can be pulled out with the pinion by heating the case and does not need any other special tools. Just 2 big screwdrivers behind the input spline/nut. The bearing is about £40. I don't fancy that one failing on the motorway. SO. The question is, if I just heat the case (leaving bevel etc intact) can i just pull the pinion out and replace that bearing?
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Yes, but you should not unless you really need to.
I would be inclined to run it a few miles and then listen for noise. Also of that bearing is unhappy the local heat will give it away.
Bear in mind that of you change that bearing you will need to completely check the shims setting the contact patch of the crown and pinon.
Chances are the existing ones will be close enough, but of they are not you are on a world of hurt.
However, if you do proceed and change the input pinion bearing, do also change the small inner bearing as it is usually this one that wears out
Be warned they can be a right bastard to get out - use heat.
However I I would run the FD and look/listen for sounds of distress.
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You are right. If it needs a full rebuild later, then so be it. I don't know if the gears are shot or not so a run will find anything there too.
A bit more elbow grease and happier. On the basis of a micron more wear vs skidding / vibrating ball race turning at 6000RPM. Pic below. I can't imagine anyone ever having this particular problem before, it's only because the inner race has been off the bike and the thing half stripped for the past ??? years. The rest of it had a good coating of oily filth :thumbsup:
(why do pics always make things look worse than they are!)
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Hello Lads and Gals,
When I studied mechanic, a teacher told us that regarding bearing, if you see something on the race the bearing is shot. If you feel something on the bearing race when running a nail on it, the bearing is double shot.
So IMHO your bearing is just good for the bin.
As per it's replacement and setting the pinion position, carefully measuring the position the pinion has with the shot bearing and setting that measure once the new bearing in place is IMHO sufficient.
Do not forget to change all slip seals on the drive unit.To remove the bearing in the body (to change the seal witch it conceal) put the housing upside down on the bench, and heat the drive unit evenly. When the proper temperature is reached, the bearing will fall with a noise on the bench. To install it, cool the bearing and heat the drive housing. Not that difficult except cleaning the old gasket.... (of course you have a beer can cut properly to protect the big lip seal when assembly time comes from the splines.... )
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;D
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:engel017:
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Hang on here. Which bearing are we actually talking about?
The initial discussion in my mind was about the input shaft bearing behind the bell coupler that connects the driveshaft to the final drive.
But the photos are of the "big bearing" that supports the output side of the "ring" gear.
Now here is the thing.
The big bearing works for a living and whilst it can have a long and happy life (coming up 50 years for some) it needs to be in perfect condition.
It's opposite number in the early final drives is a sleeve needle roller bearing which unlike the tapered roller fitted to later final drives will never know what hard work is and unless it shows signs of physical damage can be safely left alone.
The OP says it is a "finned" case final drive so I am assuming late model.
In any event replace the big bearing and the tapered roller. Then shim the damn thing properly. Ignore those that say "just bung in new bearings, put the old shims back in and just ride it" they do not know what they are talking about.
The problem is that sometimes given the precision nature of bearings if you change out the same brand of bearing you will be pretty close, possibly 50 percent of the time. That is not odds I like.
Remember I said that this bearing works of a living? It needs everything going for it.
My original comments related to the input bearing behind the bell coupler. In contrast this bearing will never know what hard work is. The same size bearing is fitted in the differentials behind BMW V12s. For the miniscule power of an airhead it is grossly over spec. Hence my "run it and see how it goes" suggestion.
Combined with the knowledge that setting up new input pinion bearings adds a further dimension of complexity to the shimming process. In other words, not trivial.
It also occurs that your photo is of a disassembled bearing. In my experience by the time a ball bearing has worn sufficiently for you to reverse the manufacturing process it is stuffed, never mind the corrosion on the race.
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It's the small dual angular input ball bearing supporting the pinion. I do not intend touching the needle rollers or large bearing on the bevel gear.
The bevel gear looks good, the pinion has some wear as do the splines, but serviceable.
I plan to replace the split ball bearing with a single piece modern equivalent. 3305-BD-XL-TVH. That is the one that had rust on one of the split inner races (it was on a shelf for years).
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For reference, the breather plug can be exchanged for a much more cost effective M18 x 1.5 Hydraulic breather.
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New bearing.
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All back together, but missing the pipe that carries the brake arm through the final drive. Part number is 33112301760. Can't see it listed in the UK, so before I start making calls, anybody got one or is it a standard bit of tube I can buy? i.e. 16mm or 5/8 etc.
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Hole is 15.86mm. Shaft is 13.85 with 14mm OD of installed O Rings.
5/8" 20 SWG ube is 15.88 OD and 14.052 ID. So will try a bit of that with loctite and/or heat as required.
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OD is a good press fit 8)
ID needs a bit of grinding to get pivot through :D
Note worn but usable splines. Gears are in better but obviously 'used' condition. I'll see what the ones fitted look like soon. Couldn't get back wheel out before now due to huge tyre, only squinted at splines for smear of moly on them.
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Just for information:
1. 5/8" 22 SWG would be a perfect size for the tube if you lose one. Needs a little sanding on the OD or heat to install.
2. My mate owes me a beer after knocking main seal in too far and managing to twang the spring out whilst doing it :dizzy2: They must be flush with the housing or the seal rides on the bearing carrier. Not quite sure how the spring came off, but the seal was replaced without lifting the cover using the correct BMW anti-nick tool on the splines. I found it by putting some oil in and leaving it on the bench (what with all the repaired threads and DIY brake tube). Wasn't expecting this bit to be a gusher!
3. Seal is an 85x65x10mm SC metric seal with single lip. A TC twin seal is available and offered by some as an upgrade - the second seal is only a dust seal (not sprung) and in this case won't contact anything anyway. I will check once I have one from Ebay in my grubby mitts.
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I couldn't find a BMW branded can, so had to slum it. This actually worked very well indeed :tekst-toppie:
Sitting on bench full of oil overnight......
No, the second seal does nothing. It might detract dust a little.
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Well this explains to poor back brake :P
Nothing visible around the outside, just slowly filling the inside! I notice this one has two brass bushes where the brake shaft goes through - another source of leaks. I assume the straight through tube was an upgrade. Big cleanup inside the drum tomorrow. I did the wheel bearing seals last time (with the wheel half out due to the oversize tyre) and it was relatively dry in there then - but I couldn't get a really good look.
Object in background is another CarbonBal balancer for a friend.
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Good news:
The new FD is on :)
There is a detectable difference in gearing :)
Bad news:
The big bearing (the one I didn't change despite my mate smacking the seal down too far onto the ball cage) growls like a dog over 40MPH :thud:
Other news:
My mate is going to have a pentagram smeared in gear oil on his front door and sacrificial gaskets hung around the periphery :furious3:
The big seal was down hard on the carrier, to the extent it had depressions on the back. I asked him how hard he had hit it after the test ride and the answer was [bullshit interpreter] "Far too much". "It's only rubber". No it has steel inside it.... It's coming off again this weekend and I'll clean and spin it before pulling it to be sure it is that and not a clearance / shimming issue. I note the old one has noticeable backlash (but makes very little 'diff' noise) and the replacement has less. Plus the gears look good to the eye. We have karma though, he swapped the mufflers for nice shiny ones and is now in a world of pain with balance pipes and parts that don't fit ;D
The unit was unknown and had half the input bearing off and multiple stripped threads. So I don't blame my friend 100%. Maybe 99... :ROTFLMAO:
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I have to take it all back. The big bearing is fine. There is no play in the gears with the cover off and big gear resting on its small shim. Which can't be right.
So I must have closed the backlash with the new nose bearing. Thoughts?
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Pics of blued main gear, wear on pinion gear.
No discernable backlash in gears with the crownwheel resting on it's shim !
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Shims are 37x47 1.4mm on gear side and 90x100 0.6mm + 0.4mm (1mm) on plain side.
Cutting some temporary shims says I need about +0.2mm on gear side (which is cheap and easily available).
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Backlash is set by the slightly conical bronze bush that sits on the underside of inwards side of the crown Whedon did you outfit back in and right way round?
The shims on the big bearing are measured to zero clearance, running clearance is set by the housing gasket.
I have rebuilt a lot of FDs and the only backlash bush I have ever replaced was in an FD assembled from parts by someone else
Too be honest it is easy to get too excited by backlash, if Prussian blue on the gears indicates a correct contact patch I would ignore the backlash.
Beware the little bearing on the end of the pinon shaft, it can fail silently and that will need up your backlash/contact patch.
It is also a bastard to change.
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RE: Bastard. It looks OK i.e the inner race that is pressed on the pinion shaft is clear and not worn.
Replacing the input pinion bearing from a 2 part to a single part has moved the pinion incrementally towards the axle. The blue is in the centre of the teeth, but there is definitely zero backlash and it complained under a very short test ride! GrrrRRRR!!! Wear on the pinion suggests it was too far back before anyhow.
I sort of get it now, the pinion is set by marks on the case and that shim should not need altering if the gears were meant for the case. I think the input ball has worn or the shim was not quite right to start with due to the pinion nose wear. My swapping it has moved it axle-ways slightly, which is just enough to take the tiny amount of play out.
The old one (which works fine with a slight and quaint MGB - whine in a closed cobbled street with high brick walls!) has loads of backlash. I think this one would be a breeze to rebuild as it's known and has not been partially disassembled / tampered with i.e no shim changes (which is how it should be as you said).
I am sure I have to increase the gear-side play and reduce the plain side on this unknown, partially stripped part though.
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I've popped the large bearing off now and put some light oil in it. It came off very easily using the holes provided in the crownwheel. Listen closely.
https://youtu.be/nsTiR0ZlOc8 (https://youtu.be/nsTiR0ZlOc8)
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Backlash is set by the slightly conical bronze bush that sits on the underside of inwards side of the crown Whedon did you outfit back in and right way round?
Pointy inner edge towards crown wheel (moving part) and turned down outer edge towards needle cage / case?
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Yes "pointy" side toward crownwheel.
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:dankk2:
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If I had a brain, I would have done this before doing anything else!
HOW TO TEST IF A FINAL DRIVE IS ANY GOOD WITH A GUN DRILL AND 24mm SOCKET:
https://youtu.be/RenY5UBd9LA (https://youtu.be/RenY5UBd9LA)