Wheel hop in the rain!

[Eatoniashoprat]

Hi,

I was really itchy for a drive yesterday and it was snowing but I took the beetle out anyway , its a driver not a show car right? Actually felt good to see ice build up on the fresh paint! It means I'm driving it and not still working on it. Anyway I found out I have wheel hop issues!

When I planned the suspension out I thought I had a pretty sweet set up but I guess I missed something, because when the car started to spin, (well, with the LSD you kinda have to work at it ), you'd get the horrible shudder. I never noticed it doing this in dry conditions but I never really 'tried' to spin the tires when it was dry, however, on the occassion it did spin wheel hop wasn't apparent.

Anyway, my set is german rubber rear mounts with a rubber/steel tranny/bellhousing strap, and a Berg mid-mount with the rubber mounts LINK, no nose cone mount (no room since engine and tranny moved ahead 2" for subaru).

I believe the problem is that the mid mount is letting the front of the tranny lift up very easily. If you pull the seat out and watch the front of the tranny and just tap the throttle you can watch the nose cone lift up *eeek*. What do you think about a solution? Either strap the tranny at the front (I'm not real fond of this idea), or just build solid pieces to replace the rubber mounts in the mid mount. I'd love to have a traction bar type solution so that it provides more support for the engine, but there isn't really much room for something like that.

Thoughts, comments? suggestions? (ramblings also welcome)

Mike

[NO_H2O]

Do you have a Kafer-Cup-Brace? That will stop the frame horns from flexing and sholud stop the wheel hop when added to what you already have.

[Eatoniashoprat]

Originally Posted by NO_H2O

Do you have a Kafer-Cup-Brace? That will stop the frame horns from flexing and sholud stop the wheel hop when added to what you already have.

Sorry, I missed a few things. I have a 3 point brace Kafer brace (v-dub engineering), gas-adjusts, and urethane TB bushings.

The main thing that really bothered me was seeing the trans nose cone moving up and down so easily <- the face I made

[vwnewb88]

do you have a roll bar? tie the roll bar into the frame horns... thats what i did

[vwnewb88]

and they make solid mounts but it makes for a horribly noisy ride, and you feel EVERY little bump/vibration

[petevw]

Originally Posted by vwnewb88

and they make solid mounts but it makes for a horribly noisy ride, and you feel EVERY little bump/vibration

I liked my setup when the motor/trans was solid mounted. Shifting was super smooth, and the entire motor was balanced so no wierd noises/vibrations.

Solid mounted with a TGFab brace, solid strap mount at the framehorns and a quiet strap mid mounted. No wheel hop issues in a heavy 1302.

Pete

[spannermanager]

I dont think the sound was wheel hop as we normaly think of it, as your description suggests a slippery road and a limited slip diff, its possible it was the diff action causing it. ive come across this with salisbury type diffs ( plate type) i.e ZF, when the lightest wheel 'judders' slightly as it searches for grip, mainly on a high percentage preload, say 75% 'ish...
,it could be the trans movement in which case you need a better front mounting, i had a box moved right forward like yours and used a simple welded in lower strap and removable top part to clamp it solid, a bit like the ones you can buy, no front mounting, it was removed, worked fine for years, hope this helps...

[evilC]

Originally Posted by Eatoniashoprat

Sorry, I missed a few things. I have a 3 point brace Kafer brace (v-dub engineering), gas-adjusts, and urethane TB bushings.

The main thing that really bothered me was seeing the trans nose cone moving up and down so easily <- the face I made

With the Scooby engine you are adding a significant extra weight on the end of a cantilever (the horns). Also, the power generated by a EJ20 T will put a considerable torsion load into those stressed horns as well. With the relatively solid mid mount I suspect its all rotating around that especially if you have a soft front mount. My first suggestion would be to use a stiffer front mount and dispense with the midmount it can then only rotate around that front mount. Solid mounting the rear mount I am told does not necessarily increase NVH but I would only treat that as a desparate solution.
Because of the weight of the whole drivetrain the rear end ought to be stiffened and a 5 bar cup brace should be used. The 5 bar unit creates a triangulated structure that provides a very stiff unit whereas the 3 bar just tries to hang the horns off the forged arm that the top damper mount hangs on - it wasn't designed for the forces involved and is a structurally unsound principle. As you have a Scooby then heat exchangers are not a problem so a 5 bar unit will fit - right?
Spannerman has got a point about the ZF lsd especially in the traction/no traction circumstances of late season snow/slush driving

Good to see you out of hibernation!

Clive

[Eatoniashoprat]

Originally Posted by spannermanager

I dont think the sound was wheel hop as we normaly think of it, as your description suggests a slippery road and a limited slip diff, its possible it was the diff action causing it. ive come across this with salisbury type diffs ( plate type) i.e ZF, when the lightest wheel 'judders' slightly as it searches for grip, mainly on a high percentage preload, say 75% 'ish...
,it could be the trans movement in which case you need a better front mounting, i had a box moved right forward like yours and used a simple welded in lower strap and removable top part to clamp it solid, a bit like the ones you can buy, no front mounting, it was removed, worked fine for years, hope this helps...

That's an interesting point, thanks. If it still judders after some solidifying I'll have to go with that theory.
Good to know about your setting, thanks.

Originally Posted by evilC

With the Scooby engine you are adding a significant extra weight on the end of a cantilever (the horns). Also, the power generated by a EJ20 T will put a considerable torsion load into those stressed horns as well. With the relatively solid mid mount I suspect its all rotating around that especially if you have a soft front mount. My first suggestion would be to use a stiffer front mount and dispense with the midmount it can then only rotate around that front mount. Solid mounting the rear mount I am told does not necessarily increase NVH but I would only treat that as a desparate solution.
Because of the weight of the whole drivetrain the rear end ought to be stiffened and a 5 bar cup brace should be used. The 5 bar unit creates a triangulated structure that provides a very stiff unit whereas the 3 bar just tries to hang the horns off the forged arm that the top damper mount hangs on - it wasn't designed for the forces involved and is a structurally unsound principle. As you have a Scooby then heat exchangers are not a problem so a 5 bar unit will fit - right?
Spannerman has got a point about the ZF lsd especially in the traction/no traction circumstances of late season snow/slush driving

Good to see you out of hibernation!

Clive

Thanks Clive, I think the engine/tranny is rotating about the rear mount, I say that based on how much the tranny is moving up and down. However, I've been wrong before .

...*googling "NVH"*.... Ok, got it.

I think maybe you misunderstood my plan? I currently have NO front mount, just a rubber mid mount and a rubber rear mount. My plan was to change out the rubbers in the mid-mount for solid pieces or add a strap to the mid section like the ones offered by EMPI.
That's a good point about the 3/5 bar. IMO the 3 bar will do a good job of stabilizing (not supporting) the shock mounts, but has a limited role in supporting the engine. The ultimate solution would be a traction bar like is offered for aircooled motors since that would take a lot of the stress off of the frame horns. The only problem is I no room, and I would have to mount it to the inner fender sheet metal, most of which has been removed to fit the engine.

Mike

[Eatoniashoprat]

I figured I should update this for posterity. I saw that the mid mount bars were contacting the frame horns because the mid mount rubber was too soft. There is about 5mm clearance between them. I loosened the mid-mount and put some hard rubber in between and tightened it back up to test it out. The result was no more wheel hoppage.

That little bit of movement and when the bars made contact would cause the engine/tranny to oscillate up and down. You can get it good and sideways pretty easily now in the rain and it doesn't complain. I had to do some rigorous testing just to make sure though . All testing was done in a controlled, safe environment of course