Wheel Hop Solved - Diff Ear Mount

[jevansio]

I have suffered with wheel hop since going single. I don't think the 20 odd runs I did at Santa Pod helped this summer as it appeared to be getting worse.

 

A clunk in this thread (http://www.mkivsupra.net/vbb/showthread.php?t=229488) prompted me to order some parts from Dusty and a set of Titan solid diff ear mounts was one of them.

 

I don't know if you're aware, but the bushes in the diff ears are not available for replacement from Toyota. So when they're knackered you don't have a lot of options. New diffs are expensive And going solid mounts isn't recommended by those in the know unless you go full solid.

 

I had read a thread on SF about a fix that didn't involve solid mounts (http://www.supraforums.com/forum/showthread.php?t=393412). Basically involves flipping the bottom washer to put extra load/squash on the rubber mount, then adding spacers above to return the diff to it's correct position.

 

My plan was to use the upper half of the solid mount to replace the original upper rubber spacer, giving the diff it's precise location (just like if you were using a full solid mount).

 

Then I planned to use the flip washer trick on the underside to take up the slack the years of movement had caused on the lower rubber.

 

When I went to reinstall the bolt I realised something though. With the washer in it's original orientation it comes into contact with the solid core of the mounting (just like Toyota intended) meaning you can torque the bolt upto 90 lbs/ft as per normal.

 

But when you flip the washer you've basically changed how the thing is positioned and when you torque the thing up you're basically torqing against a rubber mount. I didn't believe this to be correct and reinstalled everything with the washer the correct way around.

 

So basically all I have done is replaced half the rubber mount with a solid piece limiting how far the diff will move, but not totally preventing movement (which is potentially bad).

 

The plus side is the install took about half an hour and was totally easy.

 

The even better thing is wheel hop is all but elliminated on my car. Up until now I couldn't rev the car and launch it on the road without mostly causing an extremely violent shock which caused me to back off instantly. First 3 times I've tried it tonight the wheels light up straight away and the back end slides about like I'm driving on ice . Every couple of times a small shudder does occur, but it's nowehere near as voilent as before.

 

Sorry for the long post but I know there have been a few threads on wheel hop, and I just wanted to share my solution of retaining a rubber mount with it's complience whilst reducing the wheel hop substantially

 

Oh and the clunk is gone too

[Swampy442]

Good info Jay, and well done

[Kirk]

Surely there's pic's?

 

Nice work J, very creative i must say!

[jevansio]

I did take some but it's not very interesting really

[Scott]

 

I was just going to go with the badge itself, but this just seemed more fitting.

[Kirk]

Oh comeon post up

 

So am i right in saying you have a solid inner piece or?

[jevansio]

Oh comeon post up

 

So am i right in saying you have a solid inner piece or?

I didn't really take the correct photo's to accompiany my text, I guess I could have a go at knocking up some cross section diagrams to illustrate what I found? They might prove more usefull than photo's actually.

 

No it's not a solid inner piece, I used the solid washer like piece,

 

Hang on while I knock something better up

[Kirk]

Ah i think i know what you mean now J, you mean the flat bit which sits against the body.

[jevansio]

Ah i think i know what you mean now J, you mean the flat bit which sits against the body.

Yes, that is normally a large rubber washer (with turret bits on), which allows the diff to move upward toward the body. Now one mine that is solid which prevents the diff moving upward. It can still move downward though as I haven't restricted that movement. My thinking is the reduced movement helps the wheelhop, while not totally fixing the diff helps it not crack the ears off/diff casing with sudden shocks

[jevansio]

Well I've done the diagrams so I am going to post them even if Martin now sees what I have done.

 

I did them in stages as the final diagram gets pretty confusing

 

Fig 1.

 

This is a cross section of what I believe the ear mounts internal bush to look like. The dark red is the inner solid sleeve. The translucent red being the rubber part. Note the bit at the bottom, these are turret type bits the stick out past the mount. You can see them in the bottom left following real life picture.

 

 

 

Fig 2.

 

This shows the internal bush pushed into the diffs ear mount. The solid sleeve protrudes through. The blue is obviously a cross section of the ear mount.

 

 

Fig 3.

 

This shows the original rubber spacer in place ontop. This would seperate the mount from the subframe. It constsits of a solid steel plate (shown in solid green) and again soft rubber turrets (show in translucent green). You can see it in the bottom left real photo to the left.

 

 

Fig 4.

 

This shows the bottom washer in place. This is the washer you "flip" as part of the fix. You can see it alone in the top right real picture, and held in place in the bottom left pic. Note I have not drawn the rubber/foam addition that particular washer appears to have.

 

 

Fig 5.

 

The final piece is the bolt which passes through the lot & secures everything in a solid colour (excluding the blue diff ear) to the subframe. For the diff (blue) to move up it must compress the green translucent rubber, to move down it must compress the red (translucent) rubber. These are the bits that appear to wear with age and introduce excessive movement (& I guess the wheel hop)

 

 

Fig 6.

 

This is effectively what reversing the bottom washer is trying to achieve. When you torque the bolt up you will see that it would have to compress that red rubber a hell of a lot to sit flush against the mount internal sleeve. That ain't going to happen

 

 

Fig 7.

 

What is more likely is that both the top & bottom rubber turrets compress and the diff mounting moves up. This is why spacers are introduced in the SF fix. You can also see that it's the resistance of the rubber that affects how much torque is required to get it tight. EDIT on 2nd thoughts maybe both turrets compress enough so that the washer does sit in it's original position, but I didn't want to take any chances

 

 

Fig 8.

 

My solution. The cyan is the solid upper part of the Titan kit. It prevent any movement up (being solid) and ensures the diff is held in the correct position normally. The bolt can be torqued to 90 lbs/ft as normal.

 

 

I was planning on trying a large washer (as someone did on the SF thread) to remove any more slack (rather than flipping the washer)

Edited October 22, 2010 by jevansio (see edit history)

[Scott]

Hmm, bit OT there Jay.

 

It's either Austria or Spain though?

[pistonbroke]

Apparently, this sorts the gear selection 'thunk' you get with the 6sp.

[Kirk]

Yay diagrams

 

Good fix mate!

[dwayne]

did you get a dull thud when parked and putting it into 1st and has that been fixed by this?

i've been under the car and when turning the prop by hand (while in gear) i could get the same thud. i did notice that when that thud happened the shafts were moving slightly towards the front of the car and slightly out of the diff too but we are taliking millimetres here. maybe my diff is on the way out though

Edited October 23, 2010 by dwayne (see edit history)

[jevansio]

It's funny but I never had a thud before, yet couple of times I've now heard a thud after this fix, strange.

 

Anyway been out this afternoon and the wheel hop is intermittent. If the road is flat and smooth there is no hop, but after a sustained burnout once the vibration starts, it just keeps getting worse.

 

Sometimes it's pretty bad from the get go, and bumpy parts of the road defo don't help esp if moving forward with any real speed.

 

I think I will try the "put some big washers" idea to take up some more of the slack underneath & see if it helps

[Kirk]

So effectively its reduced wheel hop rather than totaly preventing it? Would of thought with a solid mount to the chassis it wouldnt move verticaly as much.

Would a solid mount to the subframe not help and leave some give with the modified ear mounts?

[jevansio]

So effectively its reduced wheel hop rather than totaly preventing it? Would of thought with a solid mount to the chassis it wouldnt move verticaly as much.

Would a solid mount to the subframe not help and leave some give with the modified ear mounts?

Yea I would defo say it's reduced & not solved after driving it all day today, I've been launching it all over the place

 

I think my next plan of attack will be the suspension bushes, starting with the strut rods, either new units and I'll try putting the R2 bushes in to see if it makes any difference.