Another dif. bearing failure.......
08-10-2007, 09:05 AM
#1
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Another dif. bearing failure.......
Thought some might find this interesting......... This one is pretty bad as you can see. To make matters worse, the car is a 97 w/115k yet the trannsmission in it has a different vin from a '96, and the '96 tranny has been apart already also!! That's three failures, two trannsmissions, and only one car..........RS5F50V/A differential bearings FTL! Can't help but think there is more going on here than improper shimming from the factory...........
08-10-2007, 02:18 PM
#2
I've thought the same thing myself. I wonder if the elasticity of the housings is enough to put the kind of force on the bearing to cause damage as rapidly as it does. Misalignment is more likely IMHO but without putting a bunch of housings on a CMM it's going to be impossible to learn more.
Dave
Dave
08-10-2007, 06:18 PM
#3
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Dave I think you're on to it with the elasticity of the housings........Allthough I wouldn't doubt the alignment issue either, I always thought it was odd that nissan doesn't require/recommend replacing case-halves as a match drilled set.......But I think you're on to it with the cases.......
Pick up a local want-ad, find a late 80's early90's suzuki quadzilla LT500R, I can almost guarantee you that the ad will read like this --- "Completely rebuilt bottom end, new connecting rod & bearing, main bearings, top-end." And yet the owner always says he's having a kid, or is two old to ride....... Yeah, alright buddy... SURE, I bet it has nothing to do with the fact that you've had to rebuild that thing 5 times already huh?
Well in the late 80's suzuki really dropped the ball with their RM125's, 250's and the LT's as well. The aluminum casting was very weak and poor, what happens is the main crank bearings (large roller bearings similiar to an isb) outer race is allowed to spin freely in the case, this in turns causes a mis-alignment and wipes everything else out pretty early. The solution? Well there is a company that sells brass inserts to take up the slack, but they are expensive, and some expensive machining is also required. The other solution? Using a ***** punch, alternate up and down and 'dimple' the metal to make the bearing have the interference fit that it should, then, clean the aluminum 100% and wipe a small amount of high heat red locktite in the hole and seat the bearing immediatly.
Dave and Neal, thought's on this? Have you guys ever noticed how loose of a fit the outer-races are on these trannies? Have you ever noticed burnt oil streaked along the outside of the outer race indicating that the race was spinning when it shouldn't? I've done other m/t's and have not seen any of this, I can't imagine proper pre-load & final assembly would do much to stop this. Neal any way you could get your boss' opinion/advice on this thread?
Pick up a local want-ad, find a late 80's early90's suzuki quadzilla LT500R, I can almost guarantee you that the ad will read like this --- "Completely rebuilt bottom end, new connecting rod & bearing, main bearings, top-end." And yet the owner always says he's having a kid, or is two old to ride....... Yeah, alright buddy... SURE, I bet it has nothing to do with the fact that you've had to rebuild that thing 5 times already huh?
Well in the late 80's suzuki really dropped the ball with their RM125's, 250's and the LT's as well. The aluminum casting was very weak and poor, what happens is the main crank bearings (large roller bearings similiar to an isb) outer race is allowed to spin freely in the case, this in turns causes a mis-alignment and wipes everything else out pretty early. The solution? Well there is a company that sells brass inserts to take up the slack, but they are expensive, and some expensive machining is also required. The other solution? Using a ***** punch, alternate up and down and 'dimple' the metal to make the bearing have the interference fit that it should, then, clean the aluminum 100% and wipe a small amount of high heat red locktite in the hole and seat the bearing immediatly.
Dave and Neal, thought's on this? Have you guys ever noticed how loose of a fit the outer-races are on these trannies? Have you ever noticed burnt oil streaked along the outside of the outer race indicating that the race was spinning when it shouldn't? I've done other m/t's and have not seen any of this, I can't imagine proper pre-load & final assembly would do much to stop this. Neal any way you could get your boss' opinion/advice on this thread?
08-10-2007, 07:01 PM
#4
I haven't yet seen evidence of a spun bearing cup. However they have been loose enough to drop out when I disassembled it.
I usually loc-tite them in when they're like that.
It would be interesting to test the preload theory. Since we know how much preload should be there, then if I could test the housings for stiffness (I'd need a set of weights and a dial indicator) then I could calculate how much axial force is on the bearings when the tranny is cold. Then using the wheel torque I could estimate the bearing reaction forces and calculate the theoretical bearing lifespan. (I got the engineering drawing for that diff bearing from NTN NA). My impression is that the housings are flexible enough that too much preload is not a big deal - the issue I would worry about is the housing racking (losing alignment). Or just plain old not being rigid enough.
Dave
I usually loc-tite them in when they're like that.
It would be interesting to test the preload theory. Since we know how much preload should be there, then if I could test the housings for stiffness (I'd need a set of weights and a dial indicator) then I could calculate how much axial force is on the bearings when the tranny is cold. Then using the wheel torque I could estimate the bearing reaction forces and calculate the theoretical bearing lifespan. (I got the engineering drawing for that diff bearing from NTN NA). My impression is that the housings are flexible enough that too much preload is not a big deal - the issue I would worry about is the housing racking (losing alignment). Or just plain old not being rigid enough.
Dave
08-10-2007, 08:11 PM
#7
Dang that's an ugly race. I've never seen any evidence of the race spinning in the bore in a maxima. I've never had a diff bearing that seemed overly loose in the bore either, if anything, I'd say most of the races I install seem a bit on the tight side.
08-11-2007, 09:07 AM
#9
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Either way I'm calling 
on motorvate's excessive pre-load theory. How could he come to the conclusion considering you can't measure the pre-load on the old wasted bearing, and with two new bearings the pre-load is going to change. Also, look at picture A-7 in the link below, I've yet to see that on several of these tranny's. Also, take a look @ section 5.16, creep, read the discription, that sure as hell is what I have seen on both the dif's and outer-races. I think this has alot to do with it. I would be in for those calculations dave, I'f the axial load rating of the bearing proves to be a big part of the problem maybe one with steeper angles on the rollers or higher ratings could be sought..........
http://www.produkte24.com/images/cat...4/pdf_4184.pdf
^^^A very good read
on motorvate's excessive pre-load theory. How could he come to the conclusion considering you can't measure the pre-load on the old wasted bearing, and with two new bearings the pre-load is going to change. Also, look at picture A-7 in the link below, I've yet to see that on several of these tranny's. Also, take a look @ section 5.16, creep, read the discription, that sure as hell is what I have seen on both the dif's and outer-races. I think this has alot to do with it. I would be in for those calculations dave, I'f the axial load rating of the bearing proves to be a big part of the problem maybe one with steeper angles on the rollers or higher ratings could be sought.......... http://www.produkte24.com/images/cat...4/pdf_4184.pdf
^^^A very good read
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