Steering, Suspension, & Brakes

I am ready to narrow my 8.8 rear axle housing for my TR7 project. I decided to get a set of alignment bushings and a ground shaft. I was tempted to cut the tubes before I had the jig setup, but decided I wanted to see how the factory installed tubes were aligned. Interestingly, both sides have about 0.2 degrees camber. The end of each tube is about 3/32 below center. I wonder if that is intentional. I may reproduce that in my narrowed axle. The weight of the car would tend to straighten it out if anything.

What you've experienced is probably just manufacturing tolerances or possibly accident damage.
But some racers build negative camber into their axle housing on purpose.
Depending upon the length of the axles you can get away with a surprising amount.
Some really cagey guys even do it off axis to get some toe change as the suspension moves.

Cheers
Fred

Seems odd that both sides are the same if it's accident or tolerance. At least I know it should be good somewhere between where it is and perfectly straight. I was going to cut the tubes out toward the ends, but this is making me want to cut more toward the center section. A 3/32 offset in the tubes out toward the ends would be noticeable, and it doesn't seem smart structurally. Correcting closer to the center would require much less offset. I don't really want to drill the plug welds out and pull the tubes, but I suppose I could.

For those that haven't used the 1-1/4 ground shaft alignment jig, it's great. I figured I can resell the bushings pretty easily. The shaft is borrowed. It's only 3 feet long, but I can do one side at a time with it.

Rather than cutting and welding you can have the tubes bent in a frame jig.
Or an alignment shop that is used to the old straight axles and Ford I beam front ends can help you out as well.
I wouldn't straighten it at the ends either. That will just tilt the wheel bearings and cause more problems.

Cheers
Fred

I need to narrow it, so I will be cutting and welding somewhere. I could fixture it up to bend the tubes myself, but I don't like the idea of bending them.

However I go, the axle bearings will be aligned to the axle shafts. Definitely won't have any tilting on the bearing end. The way it is right now, the bearing is correct to the axle, but the splined end of the axle is 0.2 degrees out of square to the center section. The splines seem to take that up without a problem because nothing looks worn.

Mike, The problem with your measurement is you are only going from the end to center with the short bar. You really need the 5' bar all the way through. May be able to find one at a hydraulic shop. Hydraulic cylinder shaft. There was a good thread a while back on straightening axle tubes with heat on David Townsend's 8.8 he narrowed. Jim Stabe was the main contributor. Do a search or one of those guys may chime in here.

Maybe someone can convince me otherwise, but I'm confident in the short bar. I am using the center two bushings in the housing to define the centerline of the shaft, with a thou or so slip fit at each point.

I do like the idea of heating to straighten the tubes. Thanks.

Mike I think that Jim is right.
The 3 foot bar just isn't accurate enough.
You're investing a phenomenal amount of faith in the machining of the center section.
A few thou. in both saddles over a three foot (or 36,000.000") multiplier could end up being significant.
With a full length bar you remove over 50% of the variation right up front.
It gives a balanced measuring arena that tends to average any machining discrepancies in the assembly.
And you get a direct measurement at both outer flanges at the same time.
With a proper bushing at the outer end you can check the flange alignment as well.
I'm not saying that the short bar measurement is wrong.
Just that the factor for error is higher by several multiples.
My tool of choice for housing alignment is a laser.
Its deceptively simple, consisting of machined plugs that accept what is basically a laser pointer. And plugs that have a 0.004" centered orifice and a machined target area.
A dead straight housing will shine right through. But that never happens without some work.
The target area is used to calculate camber if needed.
I've straightened (bent) housings with a floor mounted anchor and a bottle jack for longer than I can remember.
With no failures ever.
Heating and quenching is also a time honored method for straightening or bending tubing of all types.
And by the way is very effective for out of true driveshafts.
If you are shortening the axle, then drilling the welds and pulling the tubes is the only way to go.
Cutting and sectioning a tube just gives another failure point and an opportunity for distortion.
Pulling the tubes is a bit of a misnomer.
As it's easier to push them out with a small bottle or screw jack and a plug that engages the tube end.
Those are my thoughts Mike.
Hope it helps some

Cheers
Fred

I'll get a longer bar today to eliminate that from the discussion.



Edited 1 time(s). Last edit at 03/14/2014 08:23PM by Addicted.

Good move Mike.
Fred, could you explain how to use the laser to check end flange trueness? I can't quite visualize it.

Jim

Re: Camber in an 8.8 rear?


Posted by: DiDueColpi
Date: March 12, 2014 03:51AM


"I've straightened (bent) housings with a floor mounted anchor and a bottle jack for longer than I can remember.
With no failures ever"

Good to hear... that's what I was thinking of doing...

" If you are shortening the axle, then drilling the welds and pulling the tubes is the only way to go."

Drill by hand? I haven't done any cutting yet (other than removing the brackets), so that's till an option.

" Pulling the tubes is a bit of a misnomer.
As it's easier to push them out with a small bottle or screw jack and a plug that engages the tube end."

Another great tip that I hadn't thought of.

thanks Fred.

Hey Jim,

The plug that has the laser in it has a flat register machined on its outer edge.
The plug centers in the bearing bore of the outer flange and the register sits flat against the outer flange.
The register has three set screws that engage the outer end of the flange to enable aiming of the laser down the axle tube.
You set up the laser at one end of the axle and install the three orificed plugs in the side bearing bores and the far outer flange.
Aim the laser through the nearest plug and then bend away to get it to shine straight through all three.
Once the axle is straight then undo the set screws to align the laser plug flat with the outer flange.
The laser will now shine on the targeted area of the side bearing plugs.
It's a simple calculation based on length of the tube and offset of the beam to figure out the flange alignment.
It's a pretty simple system. Just hard to articulate.

I use lasers for everything. From my frame table to wheel alignment rigs. Even parking indicators in the garage.
Used to buy them from an electronics wholesaler but now I just use the dollar store ones.
They work well over the short distances that I need and if you break one it's a $1.50 fix.

Cheers
Fred

FWIW, here's what I ended up doing to narrow my 8.8 and deal with the poor welding of the new flanges done by a local shop. Thanks to Jim Stabe's suggestion, I learned a ton in the process of how to heat and bend (in this case, correct) axle tubes. Before I did this, I would have sworn it couldn't be done, but I've learned otherwise. [tempusfugitgarage.com]



Edited 1 time(s). Last edit at 11/15/2014 08:41AM by DC Townsend.

In addition to which, the bearing ends themselves can be distorted (usually an egg shaped bore) by the welding process. This will in turn distort the outer bearing race when it is pressed into place, making it tight on opposite sides and loose around the ends and considerably shortening bearing life. Steve DeGroat, after several bearing failures on his shortened 8" housing took the easy approach and relieved the housings with a die grinder, opening up the tight areas and this did the job for him, as the bearings are retained by the brake backing plates.

But can someone describe a more precise, elegant, or even alternative method of dealing with this particular problem? (Obviously if the welding is done with great caution and attention it may not be an issue in the first place but let's assume that was not the case if you will.) I can't really help here, not having shortened any housings myself.

Jim

Jim,

I didn't have any issues with distortion on my new Moser housing ends. These were the 9" style housing made for the 8.8 rear end. No c-clips. Maybe they were beefier than some of the other brands available. Don't know. Even with the welding shop not listening to my instruction on keeping them square and centered didn't seem to have harmed them in any way. Bearings went in as they should have. Nice product and, real nice tech service who spent a good deal of time humoring this first time rear end narrower.

DCT

Jim & Dave,
When I did mine, I dialed in the final dimensions with a combination of torch heating and additional welding. Reflowing a few small spots around the housing ends fixed the minor out of round that I saw. Welding causes distortion, but it can also fix distortion. : )

My TR8 has about -0,5 on the rear.
No idea how they did that, but I guess they have bended the tubes.



Edited 1 time(s). Last edit at 01/17/2015 09:30AM by MadMarx.