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10-07-2006, 10:41 AM
Has anyone thought of trying to making the diff stationary, as in so in can't torque to the left to bring up the right tire?

I was wondering if this would work in eliminating 90% of the wheel hop.

During my time at Midas, I was under a lot of vehicles, european, asian, and domestic, and seeing that only domestics don't have the rear of the pumpkin bolted to something. Hell, my Skyline in Okinawa didn't have wheel hop in the rain. I would have to say it attributed to the fact that the assend of the pumpkin was bolted to the subrame.

I was looking at the Tbird subframe and seeing indented bolt holes inline with the diff cover. It looked as if Ford has used, or was planning to, this to do something with the rear end.

I was thinking that if something could be either welded, or bolted to the cover, or on the diff itself, this would limit ALOT of movement in the rear end. You would have to torque the subframe before the diff would move.

The good thing is that you would still retain the IRS, its just that the diff wouldn't be "floating" anymore...

Any input on this?

Thanks,
Stephen

90blkbrd
10-07-2006, 11:03 AM
Actually it has been done. Rich Thomson used to sell them. SCP sells them and you can find them being sold in the parts section by someone, I couldn't find the thread.

That part was copied and is now being sold for Cobra's as well.


http://www.supercoupeperformance.com/partBrowser.aspx?PartID=494


Here is another part for the pumpkin as well.

http://www.supercoupeperformance.com/partBrowser.aspx?PartID=488

10-07-2006, 11:17 AM
I know about those items...I'm talking completely different POA(plan of Attack).

Crude drawing included

10-07-2006, 11:54 AM
am i pissing in the wind on this one?

90blkbrd
10-07-2006, 12:13 PM
So you will need a way of connecting to the differential. I am guessing you will want to combine the rear differential brace and rear differential isolator support into one piece that would then spread the load into the IRS subframe at wider points than used by the rear differential isolator support.

Picture of pumpkin from rear of car.

http://www.mn12performance.com/mn12parts/diff-cover-brace/diff-brace.JPG

90blkbrd
10-07-2006, 12:18 PM
This is what a rear diff looks like in a Toyota Supra and the Lexus GS. On the back side there is two mounts that mount directly to the subframe. The GS has absolutely no wheel hop ever.

http://www.l-tunedparts.com/photos/1754/0.dat?1129206758

That link didn't quite work for me, so this one should work. http://www.l-tunedparts.com/product/?id=1754

10-07-2006, 12:56 PM
http://karljacob.typepad.com/e85viper/Differential%20In%20Box.JPG

I know this is a viper diff, just trying to show a compasion of what I am talking about. I thnk the pinion brace is and excellent idea because it actually spreads the torque of a wider area...It's just the back of the diff doesn't have the same luxury.

pic at bottom is my version...I am not savvy with photoshop or paint...leave me alone.

It still kinda give you an idea of what i have in mind.

Sharon Silver
10-07-2006, 10:32 PM
I'm kind of curious of what that looked like before you, ahem, edited it. How about posting it in it's virgin form.


http://karljacob.typepad.com/e85viper/Differential%20In%20Box.JPG

I know this is a viper diff, just trying to show a compasion of what I am talking about. I thnk the pinion brace is and excellent idea because it actually spreads the torque of a wider area...It's just the back of the diff doesn't have the same luxury.

pic at bottom is my version...I am not savvy with photoshop or paint...leave me alone.

It still kinda give you an idea of what i have in mind.

10-07-2006, 10:42 PM
its on the bottom of my post...my edited one..

seawalkersee
10-08-2006, 12:44 AM
http://karljacob.typepad.com/e85viper/Differential%20In%20Box.JPG

I know this is a viper diff, just trying to show a compasion of what I am talking about. I thnk the pinion brace is and excellent idea because it actually spreads the torque of a wider area...It's just the back of the diff doesn't have the same luxury.

pic at bottom is my version...I am not savvy with photoshop or paint...leave me alone.

It still kinda give you an idea of what i have in mind.

Thats awesome. At least you can chop that well; I am surprised I am smart enough to post pix.

Anyway. I am going to try to mount mine solid and have the suspension take ALL of the movement. If they can do it for the cobras, they can do it for me.

Chris

04-04-2007, 01:10 AM
Should be starting this project up here in the next month....I'm hoping.

Using backyard mechanic techniques and lots of 1/4 steel. I should have a mockup or something.

I know that I am kinda wasting my time, but hell...I have an idea...now i have a little extra money to do complete my idea.

David Neibert
04-04-2007, 08:13 AM
So you guys think excessive movement of the diff is the reason for wheel hop ?

David

Randy N Connie
04-04-2007, 11:16 AM
So you guys think excessive movement of the diff is the reason for wheel hop ?

David

I don't think the pumpkin movment is the largest problem.

I think fabing a wishbone shaped upper control arm.
And welding extra mounting tabs on the subframe.
Weld a tab spaced in front and behide the old tabs
that held the stock upper control arm.

When finished welding there would be four tabs
To bolt the newly fabed dual mounting wishbone
shaped upper control arm.

04-04-2007, 01:25 PM
I think that if the movement is limited for the diff, it will effectively stop or at least severely curb wheel hop. The diff pulls the right tire up when it torques to the left.

I am trying to tie the diff to the subframe so that the diff has to move the subframe before it will induce wheel hop.

I don't know...a lot of my ideas look good on paper, but I can never get them to work right. And like I said, I might be pissing in the wind on this one, but I am going to try.

David Neibert
04-04-2007, 03:58 PM
I think that if the movement is limited for the diff, it will effectively stop or at least severely curb wheel hop. The diff pulls the right tire up when it torques to the left.

I am trying to tie the diff to the subframe so that the diff has to move the subframe before it will induce wheel hop.

I don't know...a lot of my ideas look good on paper, but I can never get them to work right. And like I said, I might be pissing in the wind on this one, but I am going to try.

I don't understand how the pumpkin/diff movement can pull one tire up. The halfshafts have CV joints that allow for lots of movement of the wheels without affecting the diff, so I'm not seeing why a little pumpkin/diff movement would have much impact on the wheels ? The shafts just slide into the diff side gears and are only retained by a circlip...it takes very little force to unseat them and pull them out of the diff.

David

seawalkersee
04-04-2007, 04:15 PM
Once again, Randy has a very good point. I am going to make a mount for mine to keep it from moving (Dan Sly style). I am also going to make a mount to put the pumpkin in solid. Less movement on that end is always better.

Chris

Randy N Connie
04-04-2007, 04:21 PM
The cause of wheel hop is more than one design flaw in the rear
suspension.

Your idea of tieing down the rearend housing is one problem.
And maybe a good place to start mods to help eliminate wheel-hop.
another flaw is the upper control arms design.
Another flaw is the rubber mounted sub-frame.
And the upper or the lower control arms need some sort of a
trailing arm or radius rod.To keep wheel tire combination from
flexing forward and rearward

Randy

04-04-2007, 04:44 PM
The reason that I am looking at a little diff movement causing wheel hop is because of the way that it is mounted in our vehicles.

I have worked on quite a few cars, like I said in my first post, and the big difference I see in the Euro, Asian, and domestics rear ends are how they are mounted.

The picture above is of a Viper diff. I haven't heard of any Viper owners complaining about wheel hop except for the high hp ones, and I have to attribute it to the design of the diff. Not only for the size of the Pinion mount, but for the way it bolts directly to the body on the rear portion of it.

Yes, we do have a pinion brace, and it does a great job of spreading the load over a larger area. But I think the rear mount on our cars is a contributing factor.

Instead of having a single rubber isolator that bolts vertically to the diff, I was thinking of using an 8.8 cover from a solid axle and extending the mount to bolt directly to the subframe.

http://static.summitracing.com/global/images/prod/large/sme-8510100.jpg

Thinking of something like this, and then just making a bracket to bolt directly to the subframe.

http://www.mn12performance.com/mn12how-to/irs/IRS-Subframe-pic7.JPG

Again, the rear mount, IMO is a contributing factor. The rear mount is actually smaller than the pinion mount, so when you jump off the line, or accelerate hard out of the apex, the driveline shock is too much for the mounting points that our rear diffs have.

Again, what I am trying to do is trying to make the differential itself solid.

racecougar
04-04-2007, 06:41 PM
I don't understand how the pumpkin/diff movement can pull one tire up.

Agreed. This isn't a solid axle car that we're talking about here...IRS reacts/works a bit differently. However, I could possibly see some wheelhop occurring through the rapid loading/unloading of the diff with stock rubber mounts.

Irregardless, I don't have any wheelhop here to speak of. I'm running a diff cover brace with two bolts through the rear rubber isolator, and poly mounts up front.

Disregard the yellow circle:
http://i6.photobucket.com/albums/y207/racecougar/90%20XR7/underside/reardiffmount.jpg

http://i6.photobucket.com/albums/y207/racecougar/90%20XR7/underside/rearsuspension1.jpg

-Rod

04-04-2007, 07:50 PM
are you running with a AOD or 4R70?

I was looking to make this for the 5spd guys. I think it would help out quite a bit.

Bacondoggy
04-04-2007, 08:11 PM
ok I am confused - I understand everything everyone is saying, and I was tlking to my dad about everything - all he said was.... why would the differential cause wheel hop - and then he said something about it shouldn't because of the cv joints and they should flex even if the differential torque's to the left...

racecougar
04-04-2007, 11:30 PM
are you running with a AOD or 4R70?

I'm running a 4R70W in that car.

-Rod

Bacondoggy
04-06-2007, 06:55 PM
any comment on my post? I dont want to invest $ into any diff. brace if it doesn't do anything. Unfortunately there is alot of backwards thinking that goes on. I am NOT saying that is what is going on here, I am just saying...

scbird1
04-06-2007, 07:32 PM
Well this has been a problem for the 5 speed cars. When they were new I bet there was hardly any wheel hop. My auto with the 4R70W never wheel hopped. Im thinking that unless your putting down some major power numbers some new bushings on all the rear end should do the trick.
Mannysc had a little trick he did to stop this. Contact him

Black93sc
03-09-2008, 07:23 PM
This brace looks like it will add rigidty to the rear differential cover. The same torsional and linear (by linear I mean the load which forces the pinion upward) loads will still be exerted on the factory rubber isolator, though.



Disregard the yellow circle:
http://i6.photobucket.com/albums/y207/racecougar/90%20XR7/underside/reardiffmount.jpg

http://i6.photobucket.com/albums/y207/racecougar/90%20XR7/underside/rearsuspension1.jpg

-Rod

racecougar
03-09-2008, 09:31 PM
Holy post resurrection.


This brace looks like it will add rigidty to the rear differential cover.

That would be the intention. ;)

-Rod

Black93sc
03-09-2008, 10:26 PM
All good posts get resurected eventually. As my post explained, it looks as if it adds rigidity to the cover but does not assist with stabilizing the rear of the pumpkin as a whole because the factory mount would still be absorbing the same loadings as it would without this brace.

This bracket looks as if it would prevent the diff cover from cracking, but not help with preventing unwanted twist and pinion lift as power is applied.


Holy post resurrection.



That would be the intention. ;)

-Rod

racecougar
03-10-2008, 12:17 AM
As my post explained, it looks as if it adds rigidity to the cover but does not assist with stabilizing the rear of the pumpkin as a whole because the factory mount would still be absorbing the same loadings as it would without this brace.

This bracket looks as if it would prevent the diff cover from cracking, but not help with preventing unwanted twist and pinion lift as power is applied.

The brace isn't designed to reduce movement of the centersection. Its sole purpose is to transfer loading from the centersection directly to the rear mount, reducing the stress on the diff cover.

The bolts through the rear mount do reduce movement of the centersection.

-Rod

Black93sc
03-10-2008, 08:52 PM
Thats slick - I didn't see the bolts through the sides of the rear mount until you just mentioned it. What size bolts did you wind up using?

Thanks,
Ted


The brace isn't designed to reduce movement of the centersection. Its sole purpose is to transfer loading from the centersection directly to the rear mount, reducing the stress on the diff cover.

The bolts through the rear mount do reduce movement of the centersection.

-Rod

racecougar
03-10-2008, 09:09 PM
What size bolts did you wind up using?

It's been so long that I don't remember. Whatever I pulled out of the bins here at the shop. Looking at the picture, I'd guess that those are 1" or 1 1/4" long 5/16" bolts.

-Rod