gearbox noise
- Thread starter pat180269
- Start date
It's difficult for me to say.
From the symptoms you describe my initial diagnosis would appear to have been proven correct because the noise disappeared after those bearings were fitted. I'd be surprised if the laygear bearings were the cause as they should be permanently immersed in the oil, so that leaves the first motion shaft bearing, and the only thing that I could possibly think of for the noise to return again with a new bearing is if the shim that goes between the bearing and the bellhousing is missing. If that's not there then the bearing won't retain oil to lubricate it because it will run out into the release bearing housing.
From the symptoms you describe my initial diagnosis would appear to have been proven correct because the noise disappeared after those bearings were fitted. I'd be surprised if the laygear bearings were the cause as they should be permanently immersed in the oil, so that leaves the first motion shaft bearing, and the only thing that I could possibly think of for the noise to return again with a new bearing is if the shim that goes between the bearing and the bellhousing is missing. If that's not there then the bearing won't retain oil to lubricate it because it will run out into the release bearing housing.
If the scroll on the first motion shaft is doing its job then there's no reason that you should get an oil leak. The only other bearing that is in operation in neutral (because the first motion shaft is moving and the mainshaft isn't) is the bearing that supports the front of the mainshaft in the back of the FMS, and that also gets loaded in 1st 2nd & 3rd as the helical cut of the gears tries to force the two shafts apart, but in all the boxes I've done I've never seen one of those bearings fail, and I would have thought that if your one had failed the person who did the box would have noticed it.
If you put thicker oil in and it improves matters then all you've done is masked the symptom, not cured the problem.
If you put thicker oil in and it improves matters then all you've done is masked the symptom, not cured the problem.
harveyp6 said:
I know and it goes against the grain believe me but I am not now convinced that these boxes were all quiet.
I know some are; I have driven a 2000TC with a lovely quiet box, but it seems that some just aren't. I have had two that aren't and a couple of posters in this very thread also report noise in the lower gears. Short of pulling the box again and replacing every other bearing, which I suspect may not improve matters, I'm not sure what else I can do. The guy who did the box is meticulous and I know he would have replaced other bearings if he had any doubts about them.
I know quality control back then wasn't what it is now and that it was fairly common for cars to have what we would now consider to be noisy transmissions; I'm thinking of BMC fwd amongst others. Am I just expecting too much ?
Would trying the thicker oil have any adverse affect ?
pat180269 said:
I'd be inclined to agree with that, but I wouldn't expect a box to be quiet after a rebuild but to return to being noisy so quickly. A lot of the noisy ones were cured by fitting all the grommets correctly etc.
pat180269 said:
I'd hope that were the case, but if the shim was missing would he have known?
pat180269 said:
Rover P6's were a quality car and although I'd expect you to be able to hear something as all the cases are ally, if it's noisy to the point where it's worryingly so then it shouldn't be.
pat180269 said:
Probably not. It was common to fill them with EP90 to cure clutch spin without removing the box. In fact back in the day there were probably loads running around filled with it because people didn't know any better. "If it's a gearbox, it must use EP90......"
I think I'll try the EP90.
The shim you are talking about would that be item 3 ?
I'll speak to the guy but I sort of remember him saying he did the layshaft bearings and one at the rear. I remember the 'rear' being mentioned because I said I think the front bearing is very expensive and nearly unobtainable to which he replied that it he knew it was and that mine was ok.
The shim you are talking about would that be item 3 ?
I'll speak to the guy but I sort of remember him saying he did the layshaft bearings and one at the rear. I remember the 'rear' being mentioned because I said I think the front bearing is very expensive and nearly unobtainable to which he replied that it he knew it was and that mine was ok.
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Vern Klukas
Active Member
I have seen the bearing supporting the front of the mainshaft fail. Funnily enough, it was the very first P6 job I ever did. At the time, I put the failure down to running EP90 in the gearbox rather than the proper SAE 30.
Yours
Vern
Yours
Vern
Demetris
Well-Known Member
pat180269 said:
Although i cannot say that i have experienced a lot of P6s, i cannot believe that some of these should have a noisy gearbox, just because it happens.
Mine was tired when i got it, changed a few parts inside, and after more than 85K miles is still quiet. Not just quiet for his era, more quiet that the gearbox on the last generation of Toyota Corolla to give you a comparison to think about.
The BMC fwd cars is a totally different case and were noisy by design (transmission in the sump using 3 extra gears between the flywheel and the 1st motion shaft, design of the 1st gear teeth), again nothing to do with quality control. After all, all the cars that i can think of with similar gearbox layout i.e. PSA Douvrin were more noisy than others with end-on gearbox.
Anyway, back to your case, if the noise is again just as bad as the video you posted in the past, i would be inclined to forget about this "new" box, and rebuilt the gearbox that was originaly in the car.
Vern Klukas
Active Member
harveyp6 said:
As I recall (it was 1973 or 74) the gearbox got noisy over a couple of weeks (it was a friend's car) and then jammed in 4th. It was full of oil, but when I stripped it that bearing had collapsed completely and had destroyed the nose of the main shaft and the race in the primary pretty much welding the two together, and it was dry of oil. That's what made me decide the gear oil was too thick. Fortunately, my friend had just bought the car from a dealer who paid for the parts as the gearbox was supposed to of been rebuilt shortly before. I replaced the main shaft & primary and all the bearings. I tried to talk them into replacing the gears with a matched set, but no luck.
Yours
Vern
That's a problem I've not experienced, but the onset of the noise could be similar to the symptoms of the OP here, but as I said before, with someone doing the box who's supposed to know what they're doing, one would hope they would have checked that bearing and noticed if it was damaged. The mainshaft assmbly has to be removed from that bearing to remove the FMS and primary bearing, and doing that would make the bearing visible so there's no excuse for not seeing it.
I can't remember problems with the boxes directly associated with having EP90 in them, but from my point of view, if they had EP90 in them, then there was a little bit more cash to drain and refill with 20/50, and if that brought clutch spin problems to light, then sorting that was some more work for me... Win, win....
I can't remember problems with the boxes directly associated with having EP90 in them, but from my point of view, if they had EP90 in them, then there was a little bit more cash to drain and refill with 20/50, and if that brought clutch spin problems to light, then sorting that was some more work for me... Win, win....
harveyp6 said:
harvey you little mercenary!
harveyp6 said:
Why would the box be quiet for 100 miles I don't follow ?
I have spoken to the guy who did the box and he said he replaced the front FMS bearing and both layshaft bearings. The FMS to mainshaft bearing was to use his own words 'lovely'. I bought the box NOS and he said it is definitely 'as new' inside. He did say though that someone had removed the 'back end' at some stage because there was evidence of sealant which he thought wouldn't have been used at the factory back then. Could be this box has had a troubled past and a rebuild of another box is the best way forward.
pat180269 said:
I'd prefer to say that I was offering a first class service!
pat180269 said:
I only meant that if that bearing had failed, and we have ascertained that at least one has done so in the past, then up until the point where it failed totally and welded the mainshaft into the FMS, I'd expect the noise to be in the same gears as yours is noisy in. I can't think why if that bearing was noisy before, inspected as OK when the box was stripped, and then put back in, it was quiet for 100 miles before getting noisy again.
Vern Klukas
Active Member
pat180269 said:
The factory used sealant on the speedo drive housing to gearbox housing gasket and the gearbox housing to bellhousing gasket. Oddly, Wellseal is spec'd for the back (speedo drive) and Hylomar for the bellhousing. I'm not sure what colour Wellseal is, but Hylomar is blue.
And with regards to the FMP/mainshaft bearing, I've seen one failure & Harvey (with vastly more experience, I only fixed them for about 4 years as a job and all my other experience has come as a collector) has seen none so I suspect it is most reliable of the bearings in the gearbox.
Yours
Vern