When my vette had a TH400 auto transmission, I never, ever, ever, had any rear wheel hop issues. No matter what, smoke the tires all day long, no wheel hop.

Converted my vette to a 5spd with a TKO600, and now I have bad rear wheel hop under heavy to WOT in first and second gear. No other changes to anything else.

What is the cause of this? Does an automatic with it's fluid coupling act as a sort of shock absorber? How do I eliminate this issue?!?!?

 

Well, in answer to your question about the torque converter dampening the drivetrain shocks...yes, it does. It also provides torque multiplication at dead starts. But, I'm wondering if you've also changed tires to wider ones for better traction (than what you had on it when the THM-400 was in the car). With no other changes, I don't see why there is such a difference in rear end behavior, if the tires weren't changed.

 

I don't exactly know why it wasn't happening with the automatic but I suspect you could cure the problem with a stiffer set of rear shocks and/or different rear spring. There is a harmonic moment being set up in the rear spring that the shocks (Brits call them "dampers' for a reason) aren't controlling. It's possible that changing the rear spring could 'move' the harmonic moment of the spring to a point where the wheels won't jump up and down during wheelspin.The cheaper solution would probably be the shock route, but it sounds like you might be spending plenty on tires already!!

 

Check the rubber cushion for the pinion mount on the rear end. It's either loose or worn out.

 

I'm thinking like bashcraft,your problem is you have loosened up the diff and crossmember , maybe due to the installation of the new tranny. You might want to consider adding the 2 aluminum discs to the diff crossmember mounts and installing new upper and lower cushions to the front diff mount.
edit--- could the driveshaft be too long ?

 

I experienced the same thing. The first cheapest step is to buy the rear end cross member aluminum disk kit. About $35. Two grade 8 bolts and two disks and about 5 minutes to put them on. Once you tighten them down go test. If you still have hop I can tell you the next step.

 

First, let me give some further info. I have a healthy 406 in my vette, making 500+ HP

I made no other changes to the car other than the transmission. I do believe that the fluid coupling connection of the auto trans was dampening the drivetrain enough to not have the wheel hopping issue.

This is what I am leaning towards thinking. I may need a stiffer set of shocks and/or rear spring. My hypothesis is that with the tranny change I gained more RWHP, and that combined with the now full mechanical connection between engine and drivetrain is causing my wheel hop. I just need to know how to get rid of it!!

Not loose or worn, and it's also poly. In fact, all of my suspension is 100% poly as well. The only stock part of my entire suspension is the rear shock mounts, everything else is aftermarket and relatively new.

If it was loose or worn, explain to me how this didn't happen with the auto tranny?

I already have the aluminum diff crossmember mounts. The diff and crossmember were not touched for the 5spd conversion.

Next step please!

My curent rear suspension:

-100% poly bushings
-VBP trailing arms
-VBP adjustable struts
-Carrera 3 way adjustable shocks (set at 2)
-VBP 360# spring
-VBP 3/4" sway bar
-VBP rear diff locator discs
-Spicer 1350 u joints
-custom made 3" half shafts

Here is a pic:

 

Try stiffening the shocks to see if it helps. If nothing is loose...you're getting some good porpoise effect off the 'glass spring. Stick cars hit the tires harder and under shifts it unloads them again. The auto is much steadier and smoother and was probably hooking better also which kept tires from bouncing and spinning as bad.

I ran a 'glass spring for awhile, but went back to a 5 leaf steel one with an added leaf and QA-1 shocks to get rid of my wild bouncing ride down the track!

JIM

 

your stuff is way pretty I went from a 383 to 427 auto to a TKO 600

with a 500 + steel rear spring and I had rear wheel hop in 1-2 so bad. I thought that i would break something.

With all the fixes it came down to placing a one inch block under the rear of the tranny mount point. It does not give the front of the rear diff snubber whether made of poly, rubber, al. to move.

The drive shaft is a straight line.

It sounds goofy but ............... I have 335/35/17 street or big *** road racing slicks rear tires




Those are 3 1/2 inch exhaust pipes with a 4 inch ovaled tube cross pipe under the rear diff

 

Wow ,that sure is pretty under there.
I notice you have the left spring bolt cranked up more than the right,is that due to a body lean ?
Did you have a new driveshaft made or a new yoke installed on the old shaft ? If the driveshaft is slightly long it will bind as the differential nose comes up causing a load and unload condition.

 

I think I am going to start with the shocks. I have one more stiffer setting on my Carrera's that I will try. If that doesn't work, I will try another brand.

I already have the trans raised as high as it can go, within 1/8" of the trans tunnel, as per the instructions that came with the TKO kit.

The TKO kit came with a new driveshaft made by Inland Empire Driveline. It fit perfect, so I assume it is the correct length.


I know that there is a "traction bar" made for these cars, I am wondering if that is also something worth looking into.

 

Yeah, I had the dreaded hop once upon a time....I removed the crossmember bushings and welded in 1/4" plates, bolted it solid to the frame and made a soild bushing for the front of the diff.
No more hop, but....it does transmit a lot of noise through the frame/roll bar. Not for the squeamish

 

The traction bar just keeps the nose of the diff from coming up,pretty much what yellow 72 did with the solid bushing nose mounts.

 

7t2vette, Do you know Norval? Does he have any ideas? I lowered my my rear spring rate to 420# mono with no ill effects. I use the QA-1 single adjust rear shocks and it does seem to matter what setting they have.

I wonder if it might be your rear tires. When I had wheel hop I was also spinning the rear tires. I had what looked good 315 heat cycled crusty rears. I would go into wheel hop and have to lift off the gas and when I refloored it it would go right back into wheel hop. I did the tranny rear lift, cross disks and rear tires and it went away

 

I have a traction bar and still have wheel hop.

 

Try disconnecting the sway bar. Steve from dragvette says it can sometimes aggravate the situation and cause hop. You don't need the sway bar for drag racing.

 

The cause is the increased torque multiplication, as the TKO has a lower first gear than the T400.

Traction bar (I have one) will keep you from damaging the differential housing and/or front yoke. Won't do bupkis stopping wheel hop. I also have the aluminum cross member mounts. Can't say thay actually did anything.


The spring keeps your wheels planted and the shocks dampen the up & down motion. So a stiffer spring may help. I'd Start with adjustable shocks, Cheap and easy. If that doesn't resolve the problem, then try some of the solid mount suggestions some of the others recommend.