Rear Diff for Drag Car

Rick539 · Apr 28, 2009

Could use some help on figuring out the set-up for our drag car. It is a 95 talon with a 1G methanol engine with a 2G auto trans. Cage is done and has been curbside certified to 7.50. Been talking with IPT and they can build a tranny I hope that is capable of around 900. What ideas we need is on the rear diff setup. Have sent a couple of inquires out to Strange and Moser to see if they can build a rear spool. I haven't worked with auto diffs before. Are the axle splined the same in the manual and auto diff? We are wanting to use DSS axles but understand they are for manual diffs. I do know about the gear differences. If the axle splines are the same then it should be just a gear to housing swap? Any input would be appreciated.

ihatedsms · Apr 28, 2009

You should check with English Racing and see what they are running on there auto 1g, they made over 900 then swapped to an auto. I think they are making 826whp on the auto setup.

Jeff99GS · Apr 28, 2009

Maybe you need to step it up to a Ford 9" with Chromoly shafts :hellyeah:

sbiggi · Apr 28, 2009

Rick539 said:
Could use some help on figuring out the set-up for our drag car. It is a 95 talon with a 1G methanol engine with a 2G auto trans. Cage is done and has been curbside certified to 7.50. Been talking with IPT and they can build a tranny I hope that is capable of around 900. What ideas we need is on the rear diff setup. Have sent a couple of inquires out to Strange and Moser to see if they can build a rear spool. I haven't worked with auto diffs before. Are the axle splined the same in the manual and auto diff? We are wanting to use DSS axles but understand they are for manual diffs. I do know about the gear differences. If the axle splines are the same then it should be just a gear to housing swap? Any input would be appreciated.

The splines are the same, just different gear ratio.

SonySlave · Apr 28, 2009

ihatedsms said:
You should check with English Racing and see what they are running on there auto 1g, they made over 900 then swapped to an auto. I think they are making 826whp on the auto setup.

English Racing is using only the good 'ol stock 4-bolt rear end on Jeff Bush's drag car, auto gearing of course. They haven't gotten it to the track yet but they could still give some insight I'm sure.

http://www.dsmtuners.com/forums/dyno-talk/331684-our-auto-dsm-makes-816whp.html

English Racing

Jeff99GS · Apr 28, 2009

Get the 4 bolt shafts and diff Cryo treated!!

HighPSI TSi Guy · Apr 28, 2009

stock diff with re-inforcement on the mounting points so it doesn't twist off the mounts. The diff can hold all the power you want, it's the mounts that can't.

Rick539 · Apr 29, 2009

English gave some good feed back. And you are right about the diff not handling the twist. We ave fabricated solid bushing in the cross memeber where the diff connects and are plating the front portion of the diff on both sides. This should lock in the diff quite well. With solid brass bushings in the rear suspension and our cage load points, should make the rear diff solidly mounted

AWD_Hybrid · Jul 3, 2009

Rick I don't know the front diff gearing in a 2g auto to calc the gearing
I know the 1g inside out & the rear diff is underdriven by .00769
Locked 50/50 the rears are 66½" short over the 1/4 mile
Locked with lsds both ends, mine shows 5/16" underdriven on the rears
My compensation is 215x45x17 front & 245x40x17 rears = 5/16" diff
This rolls correctly with my odd tyres. I could overdrive by .004 if I
get 25/23 custom transfer case gears made for my 1g.
That would be 5/32" advanced at the rear instead of 5/16" under
If you look at a launch, rears bog to less circ & the fronts expand
So overdriving the rears by a poofteenth is more suited for the drags
The cheapest rotation fix is tyres by checking it on the hoist.
Cheers !

e85_4g63 · Jul 3, 2009

^ I don't understand any of this, but it sounds cool!

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Rear Diff for Drag Car

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