Went to the dragstrip today. (protip: don't go to the dragstrip.)
 

First run, I wheelhopped badly at the launch, missed 5th, and still went 13.9 at 98mph.

Second run:


:bang:

"its probably the rear end"

Dont forget to mention you were on the nt01's as well

dam that sucks... At least you hit the 13.9 tho.

:mad:

Attachment 213328

Attachment 213329

I really hope the case isn't borked :(

ball-sack...

bag of ass. sucks man

damn... wtf? the 1.8 rears usually hold up better than that.

I had a premonition about this.

on a side note, what bov are you running, and how is it routed?

ouch sucks.

Ouch. Was that a Torsen?

yes, i was actually talking about you at the track last night, were hoping his R & P didn't get into the torsen itself like yours did a few months back.

yeah, 94 type I

Maybe you'll luck up and something didn't break. Maybe your broke the R&P and cracked the case, but your torsen survived, or something like that. I have a few questions for you about that rear end so maybe others can learn. Did you install the torsen in it? What backlash and preload were your running? This isn't what I want to see as I want to weld my rear end...

Yep, I think drag racing is harder on the car than just about anything. That launch is so abusive, yet so critical. I say you pick up an open 1.8 rear and weld it up. Then you'll have your drag racing rear ready to bolt up. :bigtu:

RX7 clutch type is in your future.

+1, that's what I'm doing. Something has to fail for the diff to go. Usually one thing fails, like the ring or pinion, then that blows up, gets in torsen, breaks it, then binds up and cracks the case. Key is figuring out what breaks first. If I weld my diff, it will never break. R&P is known to be the weak link, so setting that up on the tight end of spec or tighter will save it. FWIW, minimum backlash for a 1.8 diff is .0039. I'll be doing mine .0030 or so.

I like your reaction:

"I'm going to go buy some parts."
Track guy: "Yep!"

man, that sucks. my dad just blew the 1.6 open in his miata (stock power mind you), and it sounded a bit like that.

http://a163.ac-images.myspacecdn.com...222da810d2.jpg
From cousins AE86 . . bought the car like that . .
from what i could hear in your vid, they sounded nearly identical.
:sad2:

that sucks. i am waiting on my 1.6 to explode. and on how i drive the car, i dont know how it hasnt happened yet

im pretty sure ill blow my 1.6 rear end if drive my miata daily. thats why i dont drive it :)

dude is this at sacramento raceway? cause i think i was there

Oh Snap!
 

damn im pretty sure it WAS YOU at the sac raceway cause my friend GOT IT ON CAMERA:

Small world.

Sucks to hear Sav. I assume the plan is to avoid the dragstrip in the future?

Our diff's suck balls, even the 7's. We (anyone) need to start upgrading to the RX7 Turbo II's (8") if we (anyone) wants real drag racing.

I hope to do a few passes later this year, but will ease it off the line as a 3.636 isn't cheap, nor is a good RX7 clutch pack diff.

Just putting this in here - I have an open and a welded diff and the housing if you need a replacement :P

I'll also have a spare rear housing (rx7 unit) one fedex delivers my shit that's been sitting in a warehouse 20 minutes away for the last 4 days.

13.7, not bad. I'm sure wheelhop killed it. Its bad.

I went to 1/4 Friday and ran best of 13.7 @ 102 and for a change nothing broke.

Good luck on the repair.

I was hoping it was an open and that my failure last year was just a fluke, but now you have me worrying..

If you want another Torsen, I know Blake @ www.isellmiataparts.com just picked up a '94 with a Torsen.

Nah, I'll go back. Just need to prepare the car properly. Poly diff/motor bushings/mounts to limit wheelhop, and I am going to do some research into a real rear end. If the Rx7 rear won't do it, mabye the 8" TII is the ticket?

I am installing the same. It seems like a bandaid solution, that might not even work, it should limit wheel hop, but is wheel hop what is grenading the ring and pinion? Or is the torque simply shearing them off.

I honestly have no clue.

Nice launch. ;) You wanted a new diff anyway.

Nah, it was a really crappy launch, like a 2.12 60".

I was hoping it was just the R&P, and I could throw a new one in with my Torsen and case and be done.

Ohhhhh, no.

Attachment 213322

Attachment 213323

What one of the 4 parts of the Torsen are supposed to look like:
Attachment 213324

What 1 of mine looks like:
Attachment 213325

What the other two look like:
Attachment 213326

:giggle:

R&P is chipped, Torsen is totally trashed, and the case is cracked. Total writeoff.

:owned:

Expensive night. Time for a 3.9 or 3.636.

ok so the moral of the story: torsens suck for clutch dumps. the end.

It looks like you chewed an internal torsen gear, the diff froze, and then ripped the meatball right out of the bearing retainers. ouchie.

Yeap, same thing that happened to ApexOnYou, torsen died and took the rest with it. That sucks. Well, I'm definately scratching torsen off my list. Welded diff for me. What are you going to do Sav? I think a welded open diff would be cheap and super strong if it's welded up right. And I hate your for having a 2.1 60' time.

Why not just install a Ford 8 or 9 inch? Arent they supposed to be indestructible?

Perfect for drag racing, and a live axle vs IRS is moot when it comes to track racing.

Our 7" differential isn't the weak link IMO. Well, it sort of is. Wheel hop is what kills shit. Our diff winds up like a spring when you launch it. The front of the diff jumps up and nothing stops it. Look at how the RX7 diff is mounted. Ours needs to be supported just like that, with a brace between the frame rails holding the front of the diff. Stop wheel hop and the diff's would stop breaking.

A 2.1 60' on street tires is not bad at all.

Looks like the exact same gears went on both of ours. One of those side gears went on mine, and two or three others split clean in half when the whole unit locked up. I wonder if cryo treating would help any?

And for the record, I wheel hopped for the first time the run before I broke mine too, so maybe that has something to do with it.

This car is primarily a track/autocross car, but I want the ability to go to the strip, put on the R-comps, and click off some 2.0 60 foot times. Welded diffs aren't an option. I am looking into a hybrid Rx7 option, and I need to do more research into (read: someone needs to tell me about) an 8" Rx7 TII diff.

edit: the 2.1 was on NT-01s. Not drag radials, but not street tires.

Uh, wheel hop has everything to do with it! There's no doubt. That's putting 10x the force on the diff, and stuff breaks. Our 7" diff is plenty big. We don't need a 9" rear end. We need to brace the thing to stop wheel hop.

Cryo treating would help, but it's a band aid approach. The diff being weak isn't the problem. It's wheel hop that kills it. Kinda like knock on an engine. Dosn't matter what you have if you have knock, it will break your shit. If we didn't hop our rear ends would be much much better off.

FWIW, I think it needs a pair of frame rails that tie to the factor rails and the rear subframe, and then brace the diff off of these.

.
I just sold a 1990 RX-7 TII with a LT-1 put 365hp to the wheels and had the worst wheel hop I have ever driven. I used poly on every point and welded the front of the diff to the mount to try and fix the hopping and nothing was fixing it. The RX-7 mount is NOT the answer.

You guys dont think an ace hd w/6 puck going from 0 to 7k in an instant has anything to do with diff failure?

I don't know RX7's well, but something had to be giving for it to hop. On our miata's, the front of the diff is just not supported. What do you think was giving on the RX7 for it to hop? Again I've been under an RX7 twice, so not real farmiliar with them, but I know they have a brace that holds the front of the diff. Granted, it was all connected with bushings.

Please elaborate. Sure it has something to do with it. You put down several hundred ft/lbs of torque to the rear wheels in first gear. The diff can lay down that torque, say 700 ft/lbs. But hop and it goes 700, then 200, then 1500, then 100, then 2100, etc. It beats on it and breaks stuff.

someone please define the term "welded diff" for my noobish self....

It's when you weld up the spider gears in a stock open differential. This locks the differential so that both wheels ALWAYS turn the same speed. Great for drag racing. And that's about it. Sucks in the turns, dangerous as hell in the rain, makes the car push (understeer like a bitch), it's hell on axles, etc. But it will give incredibly predictable and consistent launches.

Sav, get some 3.3 or 3.6 gears and have them cryo'd and shot peened, and get some diff mounts. Set your Konis to full stiff in the back, and cross yo fingas! You can track this set up and take it to the strip.

Don't you mean full SOFT?

R-Compounds aren't very effective for drag racing. The sidewalls are WAY too stiff and most don't have a lot of stick unless they are hot. You'd probably be better off with streets running low PSI.

Installing a larger diff. won't solve wheelhop, and that needs to be eradicated.

You all need to look at some of the V8-swap Miata guys and what they've done to reduce/eliminate wheelhop. A few of them have fabricated longitudinal links that connect the lower rear A-arms to the frame rails, and that seems to pretty much eliminate the problem.

I would also think your tires had a big hand in killing the diff.

maybe, I never made a pass, I though that full stiff will keep you from being too bouncy? Maybe? And maybe reduce wheel hop...? But what do I know.

Brian, can you think of anyone's build specifically? Having a hard time searching for it, but the m.net server seems to be going on and offline.

I've seen pics of that before. It made me wonder. I kind figured our factory 4 link wasn't the problem, but it could be. Perhaps supporting the front of the diff as I described and some long arms supporting the Lower A arms would do it. FWIW I've also seen people box in the 4 corners of the lower sub frame. That might help a little to.

It was either the 225/45 NT-01s or my 185/60 Falken 912s. ;) The NT-01s typically hook up in a straight line better than the 912s do.

yeah, because the car really had trouble with traction when the diff exploded :bang:

I think he was thinking, as am I, that softer sidewalls and less air pressure would limit the wheel hop which is speculated to be the killer here, not traction.

Yes, V8Nutz's is probably the nicest example, as I recall: http://www.cardomain.com/ride/398122/3

Al Cooper was the first I remember seeing, but it looks like the pics are all broken on his cardomain site: http://www.cardomain.com/ride/291686/3
He does talk about it in post #4 here: http://forum.miata.net/vb/showthread...oper+wheel+hop

There's one other I've seen, but I can't think of the guy's name. I'll post when I find more.

Damn, that's a nice car.