Who can build me a top 8.8" IRS Differential?

[saqmaster]

Hi folks,

This is my first post, so be gentle. I'm a Ford enthusiast in the UK and I am looking at using a Cobra 8.8" IRS Differential on a drag project car for next summer. The car at present (Ford Sierra Cosworth) uses a rather puny 7.5" rear diff. I do not want to go to a live axle setup and the proper Ford Touring Car spec 9" IRS differential would cost me about $5k here.

So i'm looking for two things :-

1) Any general comments regarding using the IRS 8.8" differential with approx 380bhp/340ft-lb and a 100-150hp nitrous shot (I understand the half-shafts may be a problem, but mine will be custom anyway, so I can go super strong from the start)..

2) Someone in the states who could build me a strong complete diff. I've seen the housing for sale from Ford Racing (~$500). I've read various texts that state you can use 'any' 8.8" differential unit, and other texts that say not all are compatible with the IRS setup. I'm not sure what else i'd need or where to buy them from, I guess the differential, gear set, bearing + seal set, stub axles and the driveshaft flange (can this come with the flat flange or a UJ only?), a girdle/strengthening plate?.. which is why i'd like someone to build it all up for me..

So if you can recommend a company who can build me what I want i'd appreciate it..


Please only reply if you have personal experience of the above as the replies may directly influence a potentially expensive purchase :-D

Thanks for your time..

Stu

 

[ShelbyGuy]

the housing from ford racing (its closer to $600 than $500) comes with a rear cover and a pinion flange.

the 8.8 parts interchange between the iron solid axle and the aluminum housing, but the specifications for backlash and carrier bearing preload are different (probably why guys who supposedly know what they're doing end up with noisy gear installs). some differentials do not have the groove for the circlip on the end of the half shaft, so they would need to be disassembled and have some machine work done on the spider gears in order to work in an i.r.s. application.

some guys recommend the eaton posi but i would stick with the factory traction-lock if you were thinking of going with a clutch-type differential. the eaton is just a glorified version of the gm 12bolt posi. in my not so very humble opinion, the traction-lock is superior to it (and easily rebuilt). If i were selling you a diff for your purposes, i'd try and talk you into either a true-trac or a c-locker. the locker will take more power, but some people freak out when they drive one around corners. they've been known to lurch and clunk (and its normal). the true-trac doesnt support as much power, but you're not putting down all that much power anyway (relatively speaking). the true-trac is a worm gear differential without clutches. its torque sensing but doesnt have any torque bias preload that i know of.

i am not (yet) an authorized vendor here, but i'm familliar with the cobra driveline.



1. new housing (comes with cover, pinion flange, half shaft pilot bearings and seals) ~$585
2. differential (c-locker or true-trac, probably the true-trac) ~$600
3. gearset (what ratio did you want? they're between about $160 and $200 depending) ~$190
4. install kit (pinion bearings &shims, differential carrier bearings & shims, nut, crush sleeve, gear marking compound) ~$75
5. billet flow diff housing brace ~$179
6. ford racing carrier bearing cap stud kit ~$35

setup on a new housing takes more time than a used housing. when ford does the machining, they know exactly what size the thing is so they can figure out the shims right away. shims are for the housing, not the gearset. there's definately some math involved to figure out the differential carrier shims. so be prepared to pay a little more for installation with new parts than with used. thats all im trying to say.

hope this helps, and i hope you think of me.

 

[saqmaster]

ShelbyGuy
Thanks for your detailed response. The 8.8" IRS Housing Kit on the Ford Racing Parts website shows a RRP of $535. I do have a guy in the states with a trade/wholesale account with Ford so perhaps i'll be able to obtain the parts at a good discount. This leads me to wonder what differential I could buy via FRP? I'm just looking through the list now.

Looking at the FRP site.. they offer the following.. assuming i'll want 31 spline.. :-

Open Diff, $189, obviously useless
Traction-Lok LSD, $299, what are these like?
Auburn LSD, $485, same as above, any good?
Auburn Pro LSD, $575, just seems to be a pumped up version of the above, rated for 'street'..
Torsen T2, $485, I've had success with these in FWD cars, any good for rwd drag?

Looking at those, I'd say the Torsen was looking the best.. how do you think that'd perform? I'm not limiting myself to the selection above, but it'd certainly bring down the parts cost of the differential if I could get them through FRP..

I'll be looking at a 3.27 or 3.55 gearset (power starts to drop off after 6000rpm, 23" tall tyres, target of 135mph, 1:1 C4).. 3.27 is ideal I think..

 

[ShelbyGuy]

the open diff is for people who want to install a mini-spool or other type of differential upgrade that fits inside an open case. eg., powertrax.

traction-lock is what the car has from the factory. its a clutch-type differential preloaded with an S-spring. reasonably durable, quiet, trouble-free, and cheap to rebuild.

auburn is a cone-type differential. the big knock against the auburn is that when its worn out you throw it away because the cones wear on the differential case itself. not the housing that the whole ring&pinion assembly is in, but the differential housing. where the ring gear bolts up. otherwise its cones within bigger cones preloaded with a spring. not sure what the difference is between the auburn and the auburn pro. i suppose i should go find out.

the torsen t2 is more of a road course rear end. its a torque sensing worm gear differential without clutch plates. very much like a true-trac. the t2-r is the torsen with the worm gears and clutch plates for high torque bias. i would not expect it to last long in a drag racing context.

you forgot the c-locker, which is also in the ford racing parts catalog. thats just the name for a detroit locker for c-clip cars (solid axle cars retain the axles with c-clips). thats what i would use for a drag car. on the street some guys are fine with them, and some guys go completely bananas with them. they have "unusual mannerisms" compared to other limited slip differentials.

terminators come stock with 3.55 gears and from the factory they're rev-limited to something like 6250rpm, if that helps you with a data point. heck it can do 135 in 3rd gear. you want as high numerically a gear ratio as you can live with on the street. i'll let you do the math with that tiny tire size.

 

[saqmaster]

ShelbyGuy
Yeah, I must admit i've never used a Torsen (or Quaife ATB) on a drag car. It's mainly been for fast street use and has performed well (well, until it gets icy!)..

I didn't see the c-locker on the FRP site.. i'll have another hunt for it.. i'm happy to go with this setup because the car is purely a track car, it will be trailered to events and not used on the street (although it will be road legal)..

I'll be using a C4 so 3.27 is looking good for me right now.. which using a 3.27 with some 235/50/15 tyres should give me a 135mph top end @ 6000rpm.. which I think is a good starting point..

 

[hurtindude]

the housing from ford racing (its closer to $600 than $500) comes with a rear cover and a pinion flange.

the 8.8 parts interchange between the iron solid axle and the aluminum housing, but the specifications for backlash and carrier bearing preload are different (probably why guys who supposedly know what they're doing end up with noisy gear installs). some differentials do not have the groove for the circlip on the end of the half shaft, so they would need to be disassembled and have some machine work done on the spider gears in order to work in an i.r.s. application.

some guys recommend the eaton posi but i would stick with the factory traction-lock if you were thinking of going with a clutch-type differential. the eaton is just a glorified version of the gm 12bolt posi. in my not so very humble opinion, the traction-lock is superior to it (and easily rebuilt). If i were selling you a diff for your purposes, i'd try and talk you into either a true-trac or a c-locker. the locker will take more power, but some people freak out when they drive one around corners. they've been known to lurch and clunk (and its normal). the true-trac doesnt support as much power, but you're not putting down all that much power anyway (relatively speaking). the true-trac is a worm gear differential without clutches. its torque sensing but doesnt have any torque bias preload that i know of.

i am not (yet) an authorized vendor here, but i'm familliar with the cobra driveline.



1. new housing (comes with cover, pinion flange, half shaft pilot bearings and seals) ~$585
2. differential (c-locker or true-trac, probably the true-trac) ~$600
3. gearset (what ratio did you want? they're between about $160 and $200 depending) ~$190
4. install kit (pinion bearings &shims, differential carrier bearings & shims, nut, crush sleeve, gear marking compound) ~$75
5. billet flow diff housing brace ~$179
6. ford racing carrier bearing cap stud kit ~$35

setup on a new housing takes more time than a used housing. when ford does the machining, they know exactly what size the thing is so they can figure out the shims right away. shims are for the housing, not the gearset. there's definately some math involved to figure out the differential carrier shims. so be prepared to pay a little more for installation with new parts than with used. thats all im trying to say.

hope this helps, and i hope you think of me.

heuy shelbyguy

is the torsen t2r a diff that would require the machining you speak of? "groove for the circlip on the end of the half shaft" ??

 

[ShelbyGuy]

nope. unless you get one thats been sitting on the shelf for a few years, a new t2-r will be irs-compliant out of the box.

i get my torsen t2-r diffs from http://www.on-trackperformance.com/ ask for mark.

here's a link that might prove useful, despite being a few years old: http://home.flash.net/~ivc1/cobra/diffgear.html

i have no idea if any other aftermarket diffs are irs-compliant. i do know for a fact that the t2-r, when brandy new, is.

 

[saqmaster]

ShelbyGuy

Would you mind telling me what the downsides of running the Torsen would be compared to the c-locker? Strength, traction?

 

[ShelbyGuy]

the c-locker is the good old "detroit locker" but for c-clip cars. its as strong as you'll get without going to a straight up spool.

 

[hurtindude]

nope. unless you get one thats been sitting on the shelf for a few years, a new t2-r will be irs-compliant out of the box.

i get my torsen t2-r diffs from http://www.on-trackperformance.com/ ask for mark.

here's a link that might prove useful, despite being a few years old: http://home.flash.net/~ivc1/cobra/diffgear.html

i have no idea if any other aftermarket diffs are irs-compliant. i do know for a fact that the t2-r, when brandy new, is.

i just got my torsen T2-R about a month or so ago. however i do think it has been sitting on a shelf for a few years. However i notice a sticker on the box that says "ford 8.8 zexel torsen t-2r 32 spline ifs/irs"

not sure what the ifs means, but i assume irs means it is good to go.

One thing i did notice, one of the bolts, or actually the only bolt on the outside of the diff was not tightened in all the way.

you wouldn't happen to know the spec for torquing that bad larry down would you.

hate to keep bothering ya but you are just a wealth of knowledge.

thanks again

 

[hurtindude]

ShelbyGuy

Would you mind telling me what the downsides of running the Torsen would be compared to the c-locker? Strength, traction?

i loved the torsen my f-body came with from the factory. I didn't have any problems drag racing or launching with it. F-body cars are known for glass jaw rear ends too... only 7.5" ring gear i believe. I never had slicks on it though. Thats why i am going to install a torsen t-2r into my cobra. I know it is more of a road race diff then a drag diff, but i don't ever plan on running crazy slicks or making crazy power like many here do, so it should be fine for me. Just like it was in my f-body. If it blows up i will be one pissed camper though, this thing cost almost 50 % more then the lockers. (which i passed on cuz i don't like the noise around corners)

I only was prompted to replace it after leaving a 1 legger in my cobra a few times already. My car doesn;t see a lot of beatings, has only a few thousand miles on the clock.

I could have beafed up the stocker and have been happy i bet, but i wonder for how long.

anyone know if a locker helps wheel hop though, just curious... some of my buds think it will, others say no, and as for me the jury is still out.

 

[JSpeed]

You have one other option:

http://www.dpiracingproducts.com/blkgolddifnacs.htm

These guys have been building Circle Track products for years

 

[saqmaster]

You have one other option:

http://www.dpiracingproducts.com/blkgolddifnacs.htm

Pretty expensive for what ultimately looks like a Torsen!

 

[hssss]

I am in the process of building a Lotus 7 powered by a roller 392. I have just about gotten the parts requirement, what fits what, to put together a nearly unbreakable IRS for my car. These pieces might be what you are looking for but I am a few days away from firming up the last of the info I need. What I have come up with is Tbird/Mk VIII knuckles, 03 Cobra hubs, Cobra or MK VII disk brakes, DSS level II half shafts (28 spline outer, 31 spline inner), and 03 Explorer 8.8 3.73 31 spline Track lock (what ever is stock in the Explorer for limited slip). From a Fab point I like the mounting system of the explorer diff better and I think it is stronger than the Tbird/MK VII/Cobra. I can get the Explorer Diff for about half the cost of just the Cobra housing.

If you would want a different carrier or gears installed there would be a price increase. The guy I use is a circle track racer and his primary buisness is diffs.

 

[ShelbyGuy]

and the only real difference between the cobra and explorer internals is that the explorer has the abs exciter between the ring gear and the diff. the cobra has four channel abs with an exciter ring on each half shaft.

 

[hssss]

The originator of the thread, saqmaster, ABS would probably not be an issue. I am currently debating whether the ABS would be an advantage on a 1400 to 1600 lb car with lots of tire and brakes or would it be unjustified complication.

The Cobra it would be the same as would be the 03/04 which with things tightened up and DSS level 5 shafts and hubs appears to be good for hundreds of sub 1.5 60ft runs without breakage. In my case I'm going with level 2 singe even with R1 315s the tires will be the fuse.