Well, after building my current pumpkin last year (Ford racing cover, solid pinion spacer, truetrac, 3.73) I developed some gear whine because we set the rear up incorrectly. After fixing the issue I'm still retaining gear whine between 40-55. So, I'm going to try again. This time I want to build the BEST and strongest pumpkin possible. I have already purchased a spare housing, so I'm ready to get the game plan going on what to do this time. Thus far my plan is: Ford Racing Cover, Wavetrac diff, 3.73 gear, solid pinion spacer, and Mark Williams bearing caps. Does anyone see anything different or additional that they would do to make it better/stronger? I'm a drag racing guy threw and threw, but I do drive the car on the street quite a bit. So lets see some thoughts. Also, to answer the question I do also already have the full FTBR treatment with the deluxe tie rods as well as DSS Pro Level half shafts.
Help me build the strongest IRS pumpkin possible
- Thread starter supraman1990
- Start date
- Joined
- Aug 28, 2002
- Messages
- 334
maybe get a t-bird housing instead on them caps.. that aluminum housing is prone to warping and that makes proper gear setup difficult to impossible..shouldn't be a problem with a cast iron hosing with them cast iron caps..
detroit locker would be the baddest street strip posi, but you would have to deal with the clunks and noise, true trac would be a close second..
use only timken or koyo(japan/usa) bearings. ford pinion seal, new pinion nut(purple) and new carrier shims, dont stack thin shims or use grooved stock shims, measure and get new shims from ford. use loctite 638 on the ring gear to diff surface and red loctite on the ring gear bolts. torque everything. Solid spacer, nut can go maybe 250lb/ft, or as hard as your 1/2 impact gun will get it..
Use regular gl-5 gear oil. no royal purple..
detroit locker would be the baddest street strip posi, but you would have to deal with the clunks and noise, true trac would be a close second..
use only timken or koyo(japan/usa) bearings. ford pinion seal, new pinion nut(purple) and new carrier shims, dont stack thin shims or use grooved stock shims, measure and get new shims from ford. use loctite 638 on the ring gear to diff surface and red loctite on the ring gear bolts. torque everything. Solid spacer, nut can go maybe 250lb/ft, or as hard as your 1/2 impact gun will get it..
Use regular gl-5 gear oil. no royal purple..
Why no royal purple? I'm doing this same build with an iron t bird housing and wave trac. I also have the solid pinion spacer and Bruce's ftbr IRS bushing kit. Just tired of the gear noise and what I believe to be excessive backlash clunk. Gonna try setting the diff up on the tighter side as well.
I have all listed sans the Iron housing and I'm running a True Trac. If you chose the iron housing still run the MW caps. My builder suggested not running any other gear than stock due to the flexible nature of the aluminum housing. Seeing a I'm estimating nearly 800 ft./lb TQ at the wheels with the next setup, there's not reason to gear it any lower. If you need a good builder for setup etc. let me know and I'll refer you.
Keep in mind for street or road race work the iron case IRS won't run as cool as an aluminum one and don't think they don't get hot (iron "hands down" for drag racing).
Consider replacing the diff cover bolts with studs (5/16-18 thread). Grainger sells them. This mod not really needed with iron diff case.
Double End Threaded Studs - Bolts - Grainger Industrial Supply
Using a bottom tap will capture 4 more threads just make sure you use aluminum tapping oil. The stud needs to be shorted on one side. I can get the measurements later this week if interested. Bolts beat-up on aluminum threads, studs don't! I've got 12 pt nuts on the studs.
Put your Mark Williams caps on a mill and skim a .875 long flat across the back side of the cap as shown.
Only do this on a cover with thrust pad screws like in the FRP diff cover (not doing this will focus the thrust load on the crest of the arch possibly distorting the bore. A flat surface will distribute the load over a wider area better) If they are not used don't do this mod and leave them with the full arch.
Trash the cap screws that come with the Williams caps and replace with longer ones to capture more threads as you can see. I ran a 1/2-13 bottom tap and got even more.
I wanted to stud the caps but the counter bore in the Mark Williams caps require removing a lot of material to clear the nuts which kinda defeats the purpose :nonono: That and no one makes the correct length/spec stud :bored:
That should help take your diff to the next level :rockon:
Consider replacing the diff cover bolts with studs (5/16-18 thread). Grainger sells them. This mod not really needed with iron diff case.
Double End Threaded Studs - Bolts - Grainger Industrial Supply
Using a bottom tap will capture 4 more threads just make sure you use aluminum tapping oil. The stud needs to be shorted on one side. I can get the measurements later this week if interested. Bolts beat-up on aluminum threads, studs don't! I've got 12 pt nuts on the studs.
Put your Mark Williams caps on a mill and skim a .875 long flat across the back side of the cap as shown.
Only do this on a cover with thrust pad screws like in the FRP diff cover (not doing this will focus the thrust load on the crest of the arch possibly distorting the bore. A flat surface will distribute the load over a wider area better) If they are not used don't do this mod and leave them with the full arch.
Trash the cap screws that come with the Williams caps and replace with longer ones to capture more threads as you can see. I ran a 1/2-13 bottom tap and got even more.
I wanted to stud the caps but the counter bore in the Mark Williams caps require removing a lot of material to clear the nuts which kinda defeats the purpose :nonono: That and no one makes the correct length/spec stud :bored:
That should help take your diff to the next level :rockon:
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In for measurements and length of the studs. 2" oal?
Also, what machining is required when installing the caps and what length bolts did you use on them?
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TIRES TIRES TIRES TIRES TIRES :burnout:
I was one of the first guys that ran the t bird housing IMO skip it. It did not last and Im back with aluminum. Good info above ^^^^ though I use Timken bearings only stud the entire housing. I went through the same situation as you with noise. YOU MUST USE A CASE SPREADER to set these rears up correctly and like mentioned above do not stack shims. Im also a fan of running minimums as far as tolerances are concerned. If you cant make that work then its time for some driving lessons :beer:
1:30 is the good stuff
TX2K13 - 1200hp Turbo Mod Motor Cobras - YouTube
What exactly does "did not last" refer to? Can you give some more detail as to what went wrong?
The studs needed for the FRP diff cover is a 5/16-18 UNC x 2 1/2" lg stud with 1" lg thread at 1 end (diff case side) and 1/2" lg on the nutted end.
Grainger p/n: 1DY42
TE-CO Dbl Thd Stud, 5/16-18x2 1/2 OAL, PK2 - Double End Threaded Studs - 1DY42|40452 - Grainger Industrial Supply
You will have to shorten the 1" thread length end till the end of the threads are flush with the face of the cover which will require a bottom tap (don't forget the aluminum tapping oil) which brings the stud length down to about 2 9/32" (2.281) lg.
modified Grainger stud
Don't have the bearing cap SHCS length at this time. Will try to get that info in a couple of days.
To answer your other question, you need to take the case and the Mark Williams caps to an automotive machine shop that has a rod cap holding fixture so they can mill the face of the caps to achieve the 2.0625 dia bearing OD. My caps required .028 & .025 shaved off the faces.
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That's what I wanna know :shrug:
sounds extremely bad-ass :rockon:
although some folks on here (esp some gt500 guys) have had bad luck with them, the wavetrac diff is supposedly stronger than the detroit tru-trac. also about twice the price. only mentioning this since the op wants the "strongest possible"
Will these work for the taps? Not sure if I should get straight or spiral?
WIDIA GTD Straight Flute Tap, Bottom, 1/2 , 13, UNC - Taps - 12F019|19355 - Grainger Industrial Supply
WIDIA GTD Straight Flute Tap, Bottom, 5/16 , 18, UNC - Taps - 12F025|19245 - Grainger Industrial Supply
WIDIA GTD Straight Flute Tap, Bottom, 1/2 , 13, UNC - Taps - 12F019|19355 - Grainger Industrial Supply
WIDIA GTD Straight Flute Tap, Bottom, 5/16 , 18, UNC - Taps - 12F025|19245 - Grainger Industrial Supply
Those will work fine. Don't forget the aluminum tapping fluid, that's important.
Will do. I'll let you know how it all comes together when I get home in a few months. I'd love to check out all your mods in person some day, you put a lot of ingenuity and thought into areas most overlook.
Thanks for the kudo's :beer:
These mods were going to be described on a thread I posted a while back but it didn't generate too much interest with only 3 replays so I just let the thread die on the vine :nonono:
http://www.svtperformance.com/forum...941142-ford-8-8-irs-heat-sink-diff-cover.html
Nobody bothered to ask any questions on what else was done to the diff which I would have outlined what was written here :shrug: This was not the first time I posted something out of the ordinary that didn't generate much enthusiasm which is why I am reluctant to post my stuff very often.
That's exactly what I'm talking about lol! So damn cool. If you ever sell your car, and attempt to include descriptions of all the mods like that, peoples heads will spin!
For what its worth I do all my runs on the street only time my car has been at the track is when it was bone stock. My Oem housing with 3:73 gears and lpw cover held its own for a while but I ended up with this.(wheel hop induced)
I then sourced a 96-97 cant remember what year t bird housing, stock diff, Arp studded caps, 3:73 gear, Timkin bearings, solid pinion spacer, and lpw cover.
That held up well for 4500 miles. I was running a twin turbo'd z at our local spot launched hard slammed 2nd ran out of rubber and let my wheel speed get ahead of me, peddled hooked again and stayed in it. Thats the run that cost me. I had a nasty howl from the diff on the way home so out it came.
Needless to say parts had been moving around, I bolted the caps down and went at the bores with a snap gauge and they were distorted quite a bit. I then bolted in the cylinder that is used for setting proper pinion depth and could actually move it up and down a few thousandths, That made me scratch my head.
I'm back with aluminum now, Eaton tru trac, Arp studded MW caps, Timken bearings. solid pinion spacer, and FRPP cover. I never bothered to stud the cover because in all my experience I've never had a fluid leak from my cover, that said it sure as hell wont hurt.
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For what its worth I do all my runs on the street only time my car has been at the track is when it was bone stock. My Oem housing with 3:73 gears and lpw cover held its own for a while but I ended up with this.(wheel hop induced)
I then sourced a 96-97 cant remember what year t bird housing, stock diff, Arp studded caps, 3:73 gear, Timkin bearings, solid pinion spacer, and lpw cover.
That held up well for 4500 miles. I was running a twin turbo'd z at our local spot launched hard slammed 2nd ran out of rubber and let my wheel speed get ahead of me, peddled hooked again and stayed in it. Thats the run that cost me. I had a nasty howl from the diff on the way home so out it came.
Needless to say parts had been moving around, I bolted the caps down and went at the bores with a snap gauge and they were distorted quite a bit. I then bolted in the cylinder that is used for setting proper pinion depth and could actually move it up and down a few thousandths, That made me scratch my head.
I'm back with aluminum now, Eaton tru trac, Arp studded MW caps, Timken bearings. solid pinion spacer, and FRPP cover. I never bothered to stud the cover because in all my experience I've never had a fluid leak from my cover, that said it sure as hell wont hurt.
That sucks about your diff going south. I have no experience with the T-Bird iron diff case but my understanding is they are sought after for drag racing but to what extent they are employed in that role or how well they hold-up I cannot say.
Iron is about twice as stiff as aluminum but that case is smooth and not webbed like the aluminum one. Shock loads may fracture the iron where cast aluminum will give a bit before it yields. The only thing that made me nervous were the mounting ears which is why I added those gussets. I haven't heard of too many AL pumpkins failing and they seem to hold-up well so there may be merit to what you stated.
I like the light weight and heat dissipation of the aluminum housing. With only a 2 1/2 quarts of oil trapped in that housing with no place to go like with axle tubes, then add the shitty thermal properties of iron and something tells me on a high powered road racer would turn your diff into a high velocity, high G deep fryer. I was talking to Mark over at On-Track Performance (Original builder of Bruce at FTBR blue race car) when I was purchasing my Torsen T2-R and he stated they were measuring over 260 degree sometimes getting close to 300 (just imagine those temps with an iron case). Get that hot and the fiber clutches in the Eaton Trac-Loc goes away. My cover is plumbed for an oil cooler but I first going to see how hot it gets. With the T2-R at this point I'm basically protecting the oil since it has no clutches to burn out. I did come up with an oil cooler design that I think will work better in the tight confines and low air flow behind the gas tank than a folded fin oil cooler. I'm a big fan of shedding heat where ever you can and this is a good place to do that.
One item I failed to mention with adding studs to the diff case. I use Kawi Bond case sealer on the diff cover which has very aggressive adhesive properties (RTV is not as strong and will "give" easier). The only way you can remove the cover on a studded diff is to use the thrust pad screws to break the seal (if you don't have those good luck trying to get the cover off). With bolts you can just tap the cover from the side with a plastic or lead hammer. I welded thick tabs to 4 corners of my cover so I can tap it with a hammer as well to help break the seal. Use a tiny spot of blue Loctite on the studs when threading them into the case.
This mod allows for higher torque to be applied to the nuts over bolts on that beefy FRP cover and eliminates thread stretch :rockon:
Just keep this in mind should you stud the case.
This mod allows for higher torque to be applied to the nuts over bolts on that beefy FRP cover and eliminates thread stretch :rockon:
Just keep this in mind should you stud the case.
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