black_89_vette

When the car squats to have the halfshafts parallel to the ground, it's essentially as strong as a solid axle right?

I have a larger bump stop set to make contact at parallel and not allow it to go beyond. I run a McLeod street twin clutch which hits pretty hard and have broken many parts previously.

My thinking is, If I can preload the suspension so axles are straight just for drags and have it launch on the bump stops, would I be less likely to breakage?

I'm looking for an idea to modify suspension for racing, then remove for regular driving. Could it be done?

black_89_vette

Could you install an additional set of trailing arms and run them vertically and have them adjust the squat? Something like install a bracket at the top of the wheel well and have an adjustable trailing arm but in the vertical position? Would this allow the car to squat?

I'm talking about only doing this at the track and removing for regular driving.

hcbph

Do I believe the Corvette IRS regardless of the angles is as strong as a Dana 60, Ford 9", Strange Axels etc.? No IMO.

If there was no deflection between the angles of the u-joints (meaning it's a straight shot) I believe it would be stronger than when it's not but I don't think it would ever be as strong as a properly set up straight axel housing. I think even if the half shafts were replaced with performance units it's still the u-joints and connections that would be the weak link.

I've not seen any high HP drag vehicle whether a funny car, dragster etc. run an IRS style rear end. Like anything else, there are limits imposed on any unit related to HP, torque etc.

I think they can be made stronger, but I honestly don't think you can ever make the IRS as strong as a quality straight rear end.

My thoughts.

gerardvg

Hi

The aluminium half shafts are the weak point, i had twisted a couple like licorice at a drag strip.
I got some steel ones made, never a problem since.
I don't want to stop the little rear squat there is on acceleration, transferring the weight over the rear tires helps with traction while using street tires.

Talk to Willie (383vett) see link below he is running an 84 with dana 44 rear that lifts the front wheels well of the ground. Running 10 second quarters, I know he has blown a couple of Dana 44's.
He will have a lot of information on what works for drag racing.

https://www.corvetteforum.com/forums...4-383vett.html

C409

..... The C4 Dana 44 is probably at ITS strongest with the axles parallel to the pavement ... but still not as strong as a solid rear ... weak links are the half shafts and the outer stub axles ... my understanding is that what you are proposing here is to remove "suspension" from the rear of the car ? ... I doubt that would improve the reliability of parts and might not do so much for straight line traction either ..... When I first installed the Tru-Trac differential in mine , I tried using 28" slicks ... in order to keep the fenders off the slicks , I had to use longer/taller bump stops ... I found that I was launching the car on the bump stops and it was upsetting the tires producing some inconsistent 60' times ... definitely a lane to lane (R/L) difference so I went back to the shorter stops and 26" tires and settled down the 60's ... My car is in the 1.44-1.48 range off the line ... BUT , its your car and I fully encourage experimentation ... give it a try and see how it goes ! .....

black_89_vette

With the McLeod street twin clutch , I have broken outer stubs and half shafts. I have broken the Dana 44. I have twisted the yoke on the trans which obliterated the u-joint and took out the driveshaft too. I have since replaced the half shafts with a set of Denny's nitrous ready halfshafts and all solid Spicer u-joints. I have placed larger bump stops preventing the suspension travel to go past parallel. I have camber relocation brackets now, which reduces camber change on suspension travel. I haven't tried it at the track since.

I think with the clutch I have, whenever it transfers power, it is before the car can fully squat and is going through angles, which is why the outer stubs are the weakest point, and if they hold up, the halfshafts are suspect.

In my mind, if you can eliminate the angles present, the power will be released into a straight line and reduce breakages. I just have to think of a way to achieve this.

I have a forged 383 @ 10:1
Pro System carb @ 838 cfm
AFR 195 Eliminators
230/230 @ 0.050 , 0.598" with 1.6 CC Pro Mags
1 3/4 headers with full 3" mandrel bent exhaust

I only plan on using an "altered" suspension at the and bring it back for everyday driving.

Tom400CFI

I think the clutch is your root problem. "neat" on this forum had a 383 w/the same clutch and broke everything after the transmission, too. I think that clutch just "hits" way too hard. You need some slip/cushion, not and on/off switch....IMO.

Rcklessdriver pursued a similar philosophy as you are asking about and had great success...in an auto trans car.

black_89_vette

Yeah, I've followed some of Neat's posts. I think things break cuz power is trying to go through angles.

Tom400CFI

That may contribute. But let me ask you this: How did "angles" break your trans yoke? What do the stub shafts care, what the u-joint angle is? They broke about in the middle, right? About where the splines end? You didn't break a u-joint ear off the stub shaft did you? How about your D44 that you broke? Why or how would the diff care what the u-joint angles are? It doesn't. The MAIN reason why parts break is b/c you're "hitting" them with 100% of your engine's torque, PLUS (and more impactfully) all the inertia stored in your rotating assy at launch. The McLeod twin disk simply has too much "bite", IMO. Other clutches have a little slip and that reduces peak loads on the drive train dramatically, while still producing fantastic 60' times (though they probably don't last as long).


Want some strong evidence? Let's examine Rcklessdriver's results again; in his '84, he was running a 434 or something like that, making ~6-700hp. On top of that, he was hitting it w/a 300 shot of nitrous, IIRC. That's about twice the power and tq that you've got, and he hit that IFS rear 100's of times, pulling as good as 1.2x 60' times IIRC. He did have the car set so that at full weight transfer, the axles were parallel w/the ground...but he also had an auto trans.

In comparison, he also has a '92 I believe with ~450hp and a stick shift, and even though that car has way less power and tq, I recall that it breaks way more parts due to the "hit" of the clutch.

It would be nice if he could comment in your thread as obviously, the information is better from him, than me. But the bottom line is that if you "hit" your drive train w/a hard-bitting clutch you'll break parts. You could break parts w/a stock engine and a McLeod twin disc.

black_89_vette

I should really get this. I've been meaning to for a while. Adding the 2 step from the MSD 6AL-2 and the Magnus Launch Control , I could really dial in the hit of the clutch. I just had this idea pop in my head and wanted to run it here.

Magnus

rklessdriver

It does not have anything to do the angle of the shafts or the suspension moving at the hit.... none of that.

It is 100% the fact that your clutch hits too hard. I fought this for years with my 92 6spd.... 480RWHP. Never went better than 1.77 60ft and 11.0s@128mph..... I broke everything under that car..... I had to stop racing it because I had already bought every spare rearend part in the area fixing it various times.... I couldnt get a clutch that hit soft and at the same time stood up to the power I had down track.... So I put a killer clutch in it (SPEC 3) and tried my best to just drive the car but when I messed up and came out too hard.... BAM! **** broke like crazy. Drag Radial tires didnt help either.... stuff was much more durable on soft sidewall bias slicks...

That is why I bought the 84 and built it into a dedicated race car with an Auto trans.

My 84 ended up with 722hp and then 200hp of nitrous additional.... best 1.24 60ft on IRS. Ran 8.60@155mph in the 1/4. At that power level, it would litterally crush the needle bearings out of the U Joints in 50 passes depending.... but I rarely broke anything else and we are talking stock stub axels, stock halfshafts.... the way the power hit the driveline was so much softer at the hit because of the TQ converter.

If I were you, I'd put a T350 in it.... I'll give you the numbers off my old PTC TQ Converter. You can totally duplicate the stuff I had, it was nothing top secret or anything.

At a minimum I would get rid of that dual disk clutch and get something more appropriate for your power level that can be driven easier like the SPEC 2 or CF dual friction.
Will