CoolKars

My rear t-arms need to be rebuilt. Spoke with several different local corvette repair shops, their is a difference in opinion in the replacement of the bearings. Some will use a slip fit and others press fit, I thought GM originally used the slip fit on early models and then changed to the press fit. Need some help to determine which method to use on replacing bearings.

big_G

All rear bearings are press-fit.

GTR1999

A lot of debate here over the years on this. I rebuild them and only will do press fit. If a guy wants a slip fit I'll show the machine page in the yellow pages as I walk him out.

There are a couple of guys here that do know how to make a slip, like Norval but he also does 100% maintenance on his car. The average guy is not going to tear down rear bearings to check or regrease them.

Properly set up pressed on bearings should go well beyond 80,90, 100k miles.

Gary

mandm1200

The rear bearings do not have to be removed as normal maintainance. Therefore, I would press them on.

CoolKars

Thanks for the advice, go with press fit.

Easy Mike

Now you're talkin'.

chris75stingray

about how much do you charge for rebuiding them?

GTR1999

I'll PM you some info.
Gary

turtlevette

front bearings are slip on.

Why is this instant death for the rear bearings?

Nobody has ever come up with a good reason and probably never will.

I have run a 30k mile slip on test. Both bearings slip on with no spacer. Hasn't failed yet.

Twin_Turbo

I kind of agree w/ turtle, if the inner race is not slipping on the spindle to cause damage then there's no reason why it can't be a slip fit setup, just like the fronts. Press fit is just easier to produce, a proper slip fit requies more exact tolerances than a press fit. I'm actually thinking about giving it a shot w no spacer after I find a second set of cheap spindles to use.

45ACP

There is an added safety factor by having the press fit. If you twist off the splined end, the axle and the wheel/tire assembly is still retained by the bearing, thus allowing you to roll with your usual four wheels. You even still have a fully functioning brake on the offending corner.

You can't say that about a slip fit set-up!

turtlevette

Yup, i've had my car 25 years and tend to twist an axle off a few times a year.

If you twist an axle off it will most probably be on a hard acceleration from a start in first gear. You won't be moving that fast and the caliper will tend to hold the wheel in place.

worry warts

Techno

Nope.
Mine broke putting the brakes on. As it is a weakened item it can break at any time without accelleration or braking. It is also a part of the suspension and assuming a broke spindle is going to still be there isn't something to bank on. I don't think of it as a safety factor at all.
In my case it was low speed and did stay on. Considering that it broke just by slamming the brakes on isn't a whole lot of force. The bottom line is a spindle that is going to break is already shot. How it breaks is moot. It could have broke on me 30 minutes earlier going around a 270* sweeper ramp at 60. (Or at the point in turtlevettes icon) I doubt a caliper mount is holding against this force. Not to mention the worst than the wheel coming off is the 1/2 shaft pole vault action.
That spindle was the good side. No play.

I'm guessing here but the reason the backs are pressed and fronts aren't is they are powered or driven. Take a front wheel drive car and it has pressed bearings on the front. But slip on the back. If you drive with slip fittings on driven wheels the result is something is chewed up. For the front wheel drive it was the hub got larger and the bearing became shot requiring a new bearing, which spun again and had to be replaced, again. Nickel plating the hub returned the clearance and no spun bearing problems. In this case it is a slip fit on the axle. Weird huh?


Heres a shot of a slip fit rear bearing. The bad side.


Twin_Turbo
I'm no expert on this but an interference fit falls under a rather narrow spectrum of mils. I think its from zero to about 6 or so. I don't see how a "proper" slip fit is harder to make under a +- spec volume production. A 1' Bore on a 1" shaft is an interference fit= a pressed fit.
If it was more expensive to make a slip fit then why are they on the front?
I think its some engineering thing they aren't willing to share.

I would assume that turtlevette can get away with stuff like this. Hes racing and should have a better eye on the car. Also has a rescue team, more safety gear and a better chance of not killing anyone else if there is a failure. But street cars are supposed to be set and forget. Not check them everytime you take them out.

45ACP

You are correct - it is no harder (thus no more expensive) to make a shaft the size needed for a slip fit vs. a pressed fit. It requires no more time in set-up or in machining. We are only talking about a difference of a couple of thousandths of an inch -if that- so it would make no difference to the machinist producing the part.

StickShiftCorvette

I have run slip fits on the rears for over 80,000 miles. The big advantage of slip fit bearings is that you can set the bearings easier since it is very easy to make fine adjustments. I set mine up by checking rolling drag as the shims were varied in .001" increments. Once the transition between loose and tight was established, I added .001 to .002" shims for the final setting. I had a custom set (3 spacers, .001" varation of lengths) of spacers made so I could get the .001" adjustments.

The reason that the bearings were press fit is that with drum brakes, the press will prevent the loss of a wheel in the event the spline twists off. With a disk brake car there is NO safety advantage to the press fit. GM just didn't want to provide two sets of similar parts (one with a press the second without).
The inner rear bearing cone doesn't tend to turn since it clamped end to end between the other cone, bearing spacer, shim, and yoke clamped by the yoke bolt.

45ACP

So you are saying that the entire works, retained only by the brake caliper if the axle fails, is reasonable?

It sure isn't in my book!

norvalwilhelm

I am a fan of slip fit. NOt both , just the inner. It makes maintenace easier but like Gary said I pull the bearings and axles for inspection every few years. In fact that is one job I was considering doing today. I check play, pull the axles , adjust if needed and just visually inspect , repack and put back.

turtlevette

Its possible to over analyze every pice of the car. Nothing is 100% secure and fool proof. The front wheel is held on by a 2 cent cotter pin.

Aflac

having the bearing be a press fit as opposed to a slip fit makes only 1 rotating surface as opposed to 2 if it is a slip. IMHO, it's a wear issue more than anything. Given the choice of slip or press fit, gimme press fit anyday!