• Registered: 2023-02-05
  • Posts: 4

Topic: Running a spool in rear diff

Just curious if anyone runs a spool in their car. The Atlanta race will be my third Lemons race, first as the car owner. We have a 2000 v6 mustang that has done 4 races so far. The car actually has done well at Barber and Nola for our experience. I really noticed at Nola the open diff wasn’t the best option. I would assume a limited slip would be best but wanted some opinions on a spool. I have ran a spool in my old f100 and it sucks in the rain, but has drag radials. I’m new to the road course racing scene so any input is appreciated, thanks.

  • From: Columbus, Oh
  • Registered: 2020-05-19
  • Posts: 319

Re: Running a spool in rear diff

Putting a spool in a road race car would be hilarious, in a bad way... If you want to have premature failure of wheel bearings, axle shafts, insane tire wear, and have your car skipping over the tires on every corner to the point where you're spinning out regularly, then by all means put in a spool...

You want a limited slip diff, of which there are a hundred options, running from junkyard takeouts (ford explorer 8.8 31 spline LSD is common and readily available in junkyards for cheap in the spirit of Lemons), to high performance racing specific ones.

Diffs are one of those things that are "unseen" in the car, like your camshafts, or hydramat in your fuel tank. Cheaty teams all spend freely on those things because no judge is going to ask to put a scope cam in your diff housing, and it's really not going to make you any faster.

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  • From: Newport News, VA
  • Registered: 2015-12-23
  • Posts: 621

Re: Running a spool in rear diff

I've driven the same car on a racetrack with and without welded spider gears.

If you are cornering hard enough to spin the inside tire, then a spool will improve drive out of the corner. If not, don't bother.

The hop-skip-chirp really only exists at paddock speed.

It will exacerbate the mustangness, enhancing any handling quirks in new and exciting ways.

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  • chaase
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  • From: East Meadow, NY
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Re: Running a spool in rear diff

KeiCarMike wrote:

Putting a spool in a road race car would be hilarious, in a bad way... If you want to have premature failure of wheel bearings, axle shafts, insane tire wear, and have your car skipping over the tires on every corner to the point where you're spinning out regularly, then by all means put in a spool...

You want a limited slip diff, of which there are a hundred options, running from junkyard takeouts (ford explorer 8.8 31 spline LSD is common and readily available in junkyards for cheap in the spirit of Lemons), to high performance racing specific ones.

Diffs are one of those things that are "unseen" in the car, like your camshafts, or hydramat in your fuel tank. Cheaty teams all spend freely on those things because no judge is going to ask to put a scope cam in your diff housing, and it's really not going to make you any faster.

/agree

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  • Huskar
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Re: Running a spool in rear diff

We had issues with an open diff in the Blazer and LUV spinning the inside tire.  A stock LSD made that problem go away and is still driveable in very tight corners.

The old blue Dodge truck that races at High Plains always had a open diff and raced for many years, they welded their spider gears and promptly rolled the truck the first race from spinning coming out of a corner.  There is probably a lesson in there.

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6 Reply by derekste (edited by derekste 2023-11-24 08:39 AM)

  • From: Aurora, IL
  • Registered: 2012-02-06
  • Posts: 910

Re: Running a spool in rear diff

KeiCarMike wrote:

Putting a spool in a road race car would be hilarious, in a bad way... If you want to have premature failure of wheel bearings, axle shafts, insane tire wear

literally none of those things will happen. we ran with a locked center and rear diff for half a dozen races.

KeiCarMike wrote:

no judge is going to ask to put a scope cam in your diff housing, and it's really not going to make you any faster.

jack up rear of car at bs, spin one tire. eZ.

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7 Reply by chaase (edited by chaase 2023-11-24 09:12 AM)

  • chaase
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  • From: East Meadow, NY
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Re: Running a spool in rear diff

derekste wrote:

Jack up rear of car at bs, spin one tire. eZ.

We spot them in BS/tech occasionally when they try and turn into the garage.

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1969 Rover P6B 3500S(sold) - Super G-Rover - I.O.E Winner, Class C Winner
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  • From: Queens, NY
  • Registered: 2014-05-17
  • Posts: 602

Re: Running a spool in rear diff

fastdzl08 wrote:

Just curious if anyone runs a spool in their car. The Atlanta race will be my third Lemons race, first as the car owner. We have a 2000 v6 mustang that has done 4 races so far. The car actually has done well at Barber and Nola for our experience. I really noticed at Nola the open diff wasn’t the best option. I would assume a limited slip would be best but wanted some opinions on a spool. I have ran a spool in my old f100 and it sucks in the rain, but has drag radials. I’m new to the road course racing scene so any input is appreciated, thanks.

There is going to be lots of negative comments. It comes down to if the inner tire in corners gets unloaded, than spool or lincoln locker will work out fine. If it does not, than it will cause lots of wear and tear. If its only 1 corner, than its really not worth it. Alternatively you can try to readjust the suspension to maintain tire forces so it wont spin the tire. OR go the opposite way and make sure it does, than spool would be more effective. Its a yes or a no. nothing in between kind of deal.
A clutch type LSD is ideal. Torsen style is not worth the effort.

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  • Registered: 2023-06-11
  • Posts: 68

Re: Running a spool in rear diff

stick with a LSD...

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  • Registered: 2023-02-05
  • Posts: 4

Re: Running a spool in rear diff

Thanks for all the input guys, honestly I didn’t think it would be a great idea from my limited experience with a spool but never hurts to ask. I think we will just run the old one wheel peel for now. It wasn’t really noticeable at Barber, but Nola was spinning the inside tire pretty good, we ended up just sawing the steering wheel to make it plant the tire. I will keep an eye out for a 8.8, I have a few but they will need re gearing. Both gt rears I have have 2.73 lsd

  • Mr.Yuck
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Re: Running a spool in rear diff

A "spool" rear is more for drag racing. You probably want a limited slip rear for this kind of racing.

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  • From: Newport News, VA
  • Registered: 2015-12-23
  • Posts: 621

Re: Running a spool in rear diff

Huskar wrote:

The old blue Dodge truck that races at High Plains always had a open diff and raced for many years, they welded their spider gears and promptly rolled the truck the first race from spinning coming out of a corner.  There is probably a lesson in there.

I don't think this was a truck issue, as this was the car that I have put some effort into and is in fact the one I referenced above. IRS, IFS, set up backwards (soft in the front, hard in the rear). The locked rear helped the truck, but was probably just a bandaid. Like they say, a locked rear isn't great but it's not the worst, either.

I wasn't there when it tipped onto it's side, but it drove just fine at the next race.

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  • From: Camarillo, CA
  • Registered: 2021-03-26
  • Posts: 386

Re: Running a spool in rear diff

Great question, following since I've debated welding the open diff in the 735i eventually. No actual experience here, but I've read that it can cause understeer at corner entry.

For us, we always reallocate the money and time for an LSD into getting the team+car out to HPDE's/practice days. Just an alternative option.. send it with the open and get more seat time. You'll probably have more fun, you'll work out kinks on the car, and adding another practice day under your belt will probably serve you better at the next race than an LSD will. Open diffs are pretty robust and not dangerous on track...  they're not great, but they're reliable and get the job done.

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  • From: SF Bay Area
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Re: Running a spool in rear diff

Running a Ford 8.8 diff is pushing the Easy Button.
You can easily get an Trak-Loc LSD from any GT Mustang.
Then, Ford Racing p/n M-4700-C
GT500 spring gives more preload so tighter LSD action.

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  • From: Birdsboro, PA
  • Registered: 2009-10-26
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Re: Running a spool in rear diff

We ran a spool in the back of the Boat (S10) which was later transferred to the Hombre, which is still running it years later, and finally had an axle failure after like 10 years on that rear end.  We also tried: Gov Lock, some other shitty LSD, and a Zexel torsen, and we kept putting that damn spool rear end back in.  No weird drivability issues, no weird failures, it just plain worked and made for a fantastic run up the hill at NH when you could just stand on it.  Another long time lemon car, Bert-One, has also been quite successful with the locked rear diff. 

Don't believe all the nay sayers.  Give it a try.

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