Looks like I'll be fabbing one of these up soon.

 

Our son is a CNC machinist. If machining a part is necessary and someone knows the dimensions, I'll see if he'll make a few.

 

Not probably going to need to be machined but more welded up. Looks like a pice of flat steel, spring mount, and some square tubing cut to the right dimenesion. 73jst4fun has one on his car that has been modded to increase ground clearance. We are going to take the dimensions off it and see if one can be fabbed up. Thanks for the offer.

 

VBP has one for '63-'79 Corvettes that sells for $99. http://www.vbandp.com/detail.aspx?ID=426
What's different between '63-'79 and my '80?

I'd like to know how long the bar from the spring plate to the cross member needs to be. VBP sells some nice rod sleeves and spherical ends. I have a pair of VBP tie rods left over from my front monospring conversion that I'd use if they were long enough and I could get ends with the correct thread.

I'm out of commission with a back injury now, otherwise I'd have been under my car and measured for myself.

 

Just went out and measured. From the center of the spring plate to the front mounting bolt for the diff is 17 inches. If you want to weld abracket onto the frame from the spring pad it is 21 inches. Give or take a little.

 

We can measure mine up and fabricate one for you....you have seen how mine was tapered to fit level with the exhaust...

 

Hmmm. you already got a stiff spring and you still get wheel hop.. Very strange.. I never had a wheel hop issue after only changing to a tighter spring. Something else has to be wrong..

 

I'm thinking the same thing. I just cannot see how the traction bar on the diff can help wheel hop. Maybe I'm wrong but I'd like to know the theory behind the traction bar. I have no problem putting it on if it works. Are you running anything like a traction bar. The whole rear exept the front trailing arm bushings is either soild or urethane.

 

Everything from the clutch back has been replaced or professionally rebuilt in the last year or two (including trailing arms, half shafts, etc.) and I still have wheel hop on any pavement. In fact, it's worse now that I am getting more power from the GMPP 350 HO crate engine. The motor mounts are brand new too, so scratch that theory.

I think a traction bar is worth a try. Besides, fabricating one sounds like a fun winter project. My car is packed away for the season and I am making good progress on my indoor projects. I plan to start my Corvette projects in January.

 

Traction bar is a misnomer w/ the Corvette IRS. It works like a torque arm to rigidly locate the differential. As the differential tries to rotate, the lift bar keeps it secure. This is also how the locator kit works: by adding rigidity to the crossmember and differential.

I had a nasty wheel hop problem that was cured when I installed both the locator kit and lift bar.

Mark

 

I have the wheel hop problem also,and installed the SSM bar and I think it worked but removed it after a week because of the severe bottoming out and my car is not lowered by me but of old original leaf spring sag,well the leaf is straight not curved,thought about cutting the bar in half too thin it down,hangs too low, that round bar with the heim joints looks like the way to go.

 

I'll either fab up a heim jointed bar or make a bar. Is it better to weld it to the frame in front of the diff or fab a bracket and bolt it to the bolt that holds the front of the diff?

 

I've luckily never had a wheel hop issue on mine. Not exactly sure why some do and some don't. Mine was using the aluminum discs on crossmember, polyurethane on diff mount and on trailing arms, a fiberglas spring and stock shocks.

But when I fabbed all the stuff to put the Dana 60 IRS under it....what I did was eyeball that nice big crossmember right behind the diff that is just sitting there doing nothing. So I welded a *wing* so to speak that extends out from the upper mounting area of the diff off the *sombrero* crossmember. It extends out under that one sitting there doing nothing. I drilled 4 holes and made a plate with 4 bolts welded to it. I fished the plate inside the crossmember so the bolts extend downward through the *wing*. I installed a cushion between them and installed locking nuts.

When all this is done, what you come up with is that when you dump the clutch and the ring gear tries to rotate the hole differential, it pulls downward on that wing and those four bolts keep it from moving. In my mind it takes a heck of a load off those two little studs trying to hold the whole diff under the car. The traction bar deal does the same thing sorta...as diff tries to rotate it presses upward on that crossmember in front of diff and keeps it from bouncing around. Seems to work OK, but I like mine better...no clearance issues and help support those two bolts on crossmember.

You could easily design one that just bolts between diff and sombrero crossmember.


JIM

 

I'm interested on how this works for you Gordon after you get the traction bar installed. I too have wheel hop when I over power the tires including severe wheelhop in 2nd gear at the strip.

 

I know "traction bar" is the wrong term because it bears little resemblence to the traction bars our son has on his 383 S10, but I wasn't sure what to call it instead. SSM and VBP call theirs a traction bar too.

So, what is the correct name for a bar between the spring mount plate and transmission mount plate?

 

Here in the UK, we have a similar device fitted on either end of live axles, and call them Anti-Tramp Bars.

They stop leaf springs "winding up" under hard acceleration, as the diff/axle tries to rotate oposite to the wheel direction.

The same effect will be achieved with either bar assemblies mentioned above.
They will stop the differential twisting under heavy acceleration. The 'hopping' you feel is the nose of the diff moving upwards under load. As the wheels loose traction the diff jumps back into place. This movement repeats while you keep your right foot on the gas, and is what you feel as wheel hop.

The rose jointed (heim? (UK/US translation needed!)) bar looks a more effective and smarter set-up.

However reading the original problem by Gordonm, I would be concerned as to why this problem has started. What has changed? If it is an increase in power then does everyone else with similar powered engines have the same problem.

My first thought is that work has been done on the diff crossmember, and it is not located correctly or securely. So that it can now twist where it should normally be rigid enough to prevent diff movement.
At least rigid enough to reduce the movement so as not to induce wheel hop.

In a nutshell - double check your diff and crossmember mounts. If their good then buy or build a jointed bar fixed at both ends.

Caveat - In My (humble) Opinion

 

Good question! Not sure there is a universally accepted term for use w/ Corvette IRS. I usually refer to it as a "lift" or "center" bar.

Mark

 

I have a brand new SSM one that I couldn't use without modifying it to work with my DragVette kit. I do not plan to use it now, so if someone wants it PM me.
-Patrick

 

I would love to see pictures some time. I am replacing my gears this winter and once I ran into wheel hop when I was lightly trying to hazy the tires, not really spin them. I don't want it to happen again and would love to go with your idea.
A picture would be nice

 

Gordon, You might want to try adjustable shocks too.