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Thread: Bearings "C3" Clearance
07-10-2006, 10:24 AM #1
Hi guys I'm also rebuilding my car manual gearbox/ transmission.
I'm sourcing the bearings, other than, from rovers ...because the standard bearings had polymide cages ...and were not up to the job
so sourcing steel caged alternatives.
What's C3 clearance on a bearing ...would it be a suitable substitute for a car gearbox bearing
The bearing chappy tells me it's clearance with extra built in for expansion etc ....this is the only one he is able to get as a substitute for one of them.
all the best...mark
07-10-2006, 11:28 AM #2
The extra clearance may contribute a small amount of extra looseness to the shaft and gears (if any) on that shaft. That means a bit more noise, perhaps a bit less shock load capacity. But, if it is the only one he can get, well, what are you going to do?
07-10-2006, 11:33 AM #3
Here explains it a bit ...
It's still got to be better than the very worn and very rough bearing i have there now ...me thinks
the trouble with these bearings is that they are automotive bearings ..car manufacturers have deliberately changed the sizes from standard to achieve sales only from themselves.
all the best..mark
07-10-2006, 11:48 AM #4
In many vehicle gearboxes the bearings are
retained in bores in aluminum housings.
The housing is heated to expand the bore(s)
and the bearings drop in to assemble. When
the aluminum cools off it locks the bearing
race into the housing.
It also compresses the outer race somewhat and
that may be the reason for spec-ing "C3"
07-10-2006, 11:49 AM #5
Watch them Cooper Bearings people. They have all their Fahrenheit to Celcius convertions wrong. If that's wrong, what else is?
07-10-2006, 12:04 PM #6
I'm not buying from cooper bearings ...that's just a reference I found on the web..
Most bearings in this box are a loose fit on the shafts and in the housings...I'm told this is normal for that box.
One of them just falls off the coutershaft when inverted...I'm also told this is normal by the rover gurus ..although ..I find it hard to believe
...........thinking rover had a whole bunch (job lot for all the gearboxes) of shafts made up under tolerance.
all the best.......mark
07-10-2006, 12:17 PM #7
Mark...Your last post states that the shaft is loose in the bearing inner race??? Why?? This would totally defeat the purpose of a ball bearing assembly to have a loose shaft fit on the inner race. It will only wear the shaft having it spinning on the hardened inner race. Same goes for the outer race pressed into the bearing bore. If its not a press fit or retained in some fashion it will wear out the bearing bore in no time. Your bearing C3 rating is for bearing class with the higher the number the tighter the tolerance of the matching parts, the less play in the system. Price some matched ABEC 7 bearings....cost an arm and two legs!! Best regards,Mark
07-10-2006, 12:40 PM #8
I don't know a lot about the development and design of this box ...seems that bearings are intentionally a loose fit
.maybe when the gears align ...they are subject to torque and thrust and whatever ...
and all the clearances are taken up.
maybe there is compensation for expansion and contraction..........I'm no gearbox expert ...I didn't design this one ...so I just don't know.........the designer knows ..but not I .
All the best..mark
07-10-2006, 12:50 PM #9
What's wrong with the temperatures, Forrest? Temp differences look OK to me.
Zero F is near enough -20C to a shivering man.
07-10-2006, 01:41 PM #10
I take it you have the mfr's repair/re-build
manual for this gearbox, it will be very apparent
if they want interference fits for the bearings,
they will say you need to heat the housing
to X temp in an oven to get it apart.
If they don't say that, then they want them
to simply slip into the bores.
07-10-2006, 02:14 PM #11
here is a link to the manufacturors manual of the gearbox..
bear in mind it covers two different boxes ...
mine being the PG1
alkl the best...mark