press fit advice from the press fit guru's

[A.K. Boomer]

Im trying to save the cases on a ZF-6 transmission from a ford F-450

the front main (which is a tapered bearing) has spun it's outer race and has gained clearance leading to excessive gear noise.

there are no oversize outer races that I know of so im going to be making up a sleeve for the new bearing - It's an aluminum case - the bearings OD is 4.125"

Im going with a 6061 T-6 sleeve to be left thick on the ID of the sleeve and pressed in first - im then going to bore the ID of the sleeve to proper bearing OD dimensions after its pressed and settled --- so there's two press fits to consider - one is the aluminum to aluminum sleeve which will probably be around 4.225" - the next is the outer race of the taper roller into the aluminum sleeve @ approximately 4.125"

everything is going together with locktite sleeve retainer


something I don't understand about this trans --- these are the first tapered rollers Iv seen in an aluminum trans case and it did surprise me because the case is quite a span --------- which means that when it heats up the shaft loses its tolerance due to it of course being made out of a material that expands at about 1/3rd the rate...

anyways - advice is needed and im all ears, thanks.

[Shuswap Pat]

When in doubt consult the eperts - SKF / Timken or NTN' I have sleeved lots of tapered bearings - if you do it right, you can finish the sleeve, and press/locktite it in and you are done. Check the SKF link, and it will guide you though the fit tables - they are basically the gospel!

http://www.skf.com/portal/skf/home/p...newlink=1_0_74

[Carld]

How much is the gap and have you thought about using gap filling locktite?

[wierdscience]

That's a regular job on electric motor endbells.I just roll up rings out of flatbar and weld the ends together.I have a 8" round piece of 1/2" plate welded to a 3" OD chunk of cold rolled round that I chuck in the lathe for a fixture.

I tack the ring to the plate and turn the ID and OD to the required size in one setup.On that size ,002"under on the bore and .003"-.004" over on the OD assuming the Aluminum housing is beefy enough to handle that much.Part the ring off the finished length and deburr.

Even with the shrink fit on Aluminum I will still drill and pin the sleeve into the castings in a few spots.

[A.K. Boomer]

Thanks W.S. , wow - .003" to .004" on the OD on over a 4" part? really?

Damn that sounds steep bro, im seeing an aluminum sleeve buckling at that kind of press and if it does go would it not just gall it's way in?

Carld yes thought about the sleeve retainer but this has got to be a one time fix - the outer race has gained at least a couple/three thou and rotates by hand freely - there's so much labor in pulling one of these beasts - my bro wants it done with no worries...

thanks for the info Shuswap, can't find outer race specs into aluminum yet but will check in the morning with a clear head, (or at least one hopped up on coffee)

[Rich Carlstedt]

004 " is not bad.

The expansion on a 4" diameter piece of aluminum is .0044 for a 100 degree (F)
That means, if you freeze the bushing in the freezer ( zero F) and heat the transmission body to 200 degrees, you will have a .0088 differencial in size, so you should have .004" clearance for the fit. You have to move fast, but it will work

Rich

[becksmachine]

Is there an overriding reason that you want to use aluminum for the sleeve? I would use steel. I agree that using that much fit with an aluminum sleeve would be an invitation to review your non politically correct vocabulary.

The fits weird gave are standard "heavy press" fits, eg .001" tight per inch of diameter. Might be a bit much for an aluminum case. Or maybe not, as it is a sleeve and it will not have the rigidity of a solid shaft.

Might use loctite whatever the fits you decide, it seems to make a nice anti-seize/gall material.

Dave

[wierdscience]

Thanks W.S. , wow - .003" to .004" on the OD on over a 4" part? really?

Damn that sounds steep bro, im seeing an aluminum sleeve buckling at that kind of press and if it does go would it not just gall it's way in?

Oops,forgot to mention steel sleeves.

No press fit either,shrink fit is the way.Aluminum in that size expands considerably.I did some parts in 6061 this summer,2-3/8" ID 6" OD rings shrink fitted over a 2.379" male 6061 boss.That was .004" interference,yet heated to 275f it was a drop on fit.

Not knowing how heavy your housing is use your own judgement,don't want to split anything.Getting bearing races to stay put in Aluminum bores can be a hair pulling PITA.

Here is a run down on the whole process of sleeving an endbell-

http://www.shaverkudell.ca/sleeve.html

[Willy]

something I don't understand about this trans --- these are the first tapered rollers Iv seen in an aluminum trans case and it did surprise me because the case is quite a span --------- which means that when it heats up the shaft loses its tolerance due to it of course being made out of a material that expands at about 1/3rd the rate...

I have read a rebuild manual for this transmission and I can't remember all the details but there is a specified mainshaft preload that has to be checked if any major component has been changed, also Ford is quite fussy in this regard stating only their speced sealant should be used on the case in order to preserve proper end play/preload. Of course you'll have to check this very carefully as after this repair these dimensions will have changed. Unfortunately I don't have this manual.

GM also used this transmission on older Corvettes and later in their 8L and Duramax equipped pickups. In order to make them more quiet they used a different helix angle on the gears. GM also chose to not use the oil pump/oil cooler, instead opting to allow the transmission operate at a higher temp and using a better synthetic lube to handle the heat.

Not sure what kind of service this trans will see but under long pulls I have regularly seen 13 and 18 speed cast iron manual transmissions reach 235-250°F with synthetic lubes. Knowing how much aluminum expands the .001 per inch interference fit does not seem at all out of line.

I hear ya on the PIA portion of a Re & Re, do as much research as you can until you feel comfortable about not having to do it again.

[A.K. Boomer]

Good stuff u guys thank you very much,

My reasoning for going with the aluminum sleeve is simply due to not having the proper boring tool for my boring head for steel - the diameter is bigger than my boring heads travel but I already made up a nice extender bit that should cut the aluminum no prob.
Could make up a steel sleeve and do ID and OD and then press but it's going to be so thin (to keep the case strength strong) that I know it would have a taper before part off...

the aluminum to aluminum does present a problem when heating the case up for the first press - its' going to be instant transfer to a small part - not good

So here's what im thinking guys - and please feel free to critique the hell out of this cuz if im off base on this now's the time for me to re-calibrate,

Im really not seeing an advantage for heat with the first press - and I don't want any trouble with galling cuz the last thing I need is a bunch of highs and lows with empty space in there - so - I press the aluminum into the aluminum with the sleeve retainer locktite (good to know that becksmachine also thinks its got anti-gall properties as that's been my experience too)
with only a couple thou interference...

I then machine the ID to have a .004" press/shrink fit for the outer race --- then when the steel race heats up whilst pressing and positioning (u know how it goes) im not losing all my expansion values - and its going in with the locktite sleeve retainer - it's also making the press fit of the aluminum parts very stout as the .050" sleeve just transfers the press.
the race is nice and ground hardened steel and more compatible for anti-gall and is designed for this so should be good.

Willy I read that same thing about GM --- these are noisy gearboxes and they went with a steeper helical angle to keep the noise down --- I don't like the idea of just running them at higher temps due to the expansion values of the aluminum -- GM also states that their fluid is "lifetime" or the vehicle -- to me that's crazy - it's lifetime alright cuz if you hash a trans then that's the lifetime of the vehicle - lol

I like fords approach better - keep it cool as you can - and no reason why you cant run special synthetics in them also....

Thanks for all the advice...