MEGALADON

My 406 is being built as you read this, My HP and Torqe will be
over 450 sez the shop. Problem is, I want to run a 6 speed
But I hear to much of this with my IRS, My next option
is my 4l60E trans. So I dont beat my rear with a manual trans.
I also hear, 79 and later vettes have stronger rear ends
Is this true? What is out there so help make a strong IRS
only thing I heard of, is VAN STEELS end caps for $200.00
I would think I need more than end caps. My dana will be rebuilt with
a different gear, but not sure till I figure what trans I can run.

BOTTOM LINE IS, who got big power with their 80/82 and what trans
you got, and what you done to keep your your together. I will not
run slicks, this is only a street killer, not for the trtack!!!, I will only
have 315/35-17 for rear tires

MotorHead

I am making some power, bottom line is the tires are going to break loose before you break something if everything is up to snuff in back, once you go to drag radials or slicks all bets are off

1979toy

There is a C3 in the new issue of Hot Rod that ran the pump gas drags. He ran low 9's with an IRS.
The article said that his rear had been stuffed full of 12 bolt hardware from Tom's Differentials http://www.tomsdifferentials.com/ and larger halfshafts.
I don't recall if it was an auto or a stick though.
The gear xases were steel up through '79. In 80 they switched to an aluminum case. My guess would be that the '79 and earlier would be the stronger cases.


[Modified by 1979toy, 4:14 PM 7/7/2004]

GrandSportC3

If you don't run slicks or drag radials - you shouldn't have too many problems with stuff breaking... It's not power that breaks stuff.. it's traction... Even with 315 street tires - you won't break too much... A dead hook is what causes breakage...


[Modified by GrandSportC3, 5:30 PM 7/7/2004]

Gordonm

The tires will break loose before anything else breaks.

MEGALADON

LOL, thats the point, I don't want to break to much
or to little . I prefer to fix all the weak points before the install
I take it, the breaking comes from only hard take off's right
anyone with cooling problems on big inch motors? Im hopeing this wont
be a problem either. this will not be a garage queen

Schmucker

Twin-Turbo is running a C4 rear end and I'm sure he'll be making more power than you. There is more of a market for the Dana44 because it was also used in C4s. There should be more upgrades available for it.

kanka

Hi Megladon, I run a 406 / 475 hp. in my 78' . I have a B&M TH350 trans, 2400 RPM holshot converter. Dan Van Steel built me a 4.11 rear end and also built my trailing arms all with poly bushings. I run 275/60/15 tires on the rear . I had to up-grade to titaniem u joints (the weakest part on the rear end) I also up-graded my harmonic balancer to a SFI because the standard blancer is only good to 6500rpm. I also run a composit spring from DAN Van Steel it is a 420 lbs. spring . I use K/b Gas shocks . I can fry the tires at almost any point on problems . Every thing holds togrther fine. Hope this helps.

1979toy

The 406 in my '79 is running warmer than I would like but it's livable. I have a stock style 4 core radiator, stock water pump and dual Flex-a-Lite fans. I have a heavy duty water pump on order now, I expect to have it in hand by the end of the week. Should the water pump not lwer my engine temps enough to make me happy I expect that I will reinstall the engine driven fan.
My '79 has a T350 and a 3000 RPM stall converter. There ARE traction issues!

MEGALADON

Thanks KANKA, And everyone who gives me input.
I just called tom's diff, and they said they could mount a 79
and later carrier (STEEL) housing. Adapt to my aluminium rear
carrier mount. I'll have to see how far I want to take this now.
they also said the 4L60E would not fit in the tunnel of my vette
I may have to stick to a well built 700R4

69ttop502

Megladon, I have been down this road recently with my 600+ horsepower 502 powered 69. Van Steel now has the same 30 spline inner and outer rear axles that Tom's carries. I went for the whole thing with Van Steel including offset trailing arms, rebuilt Diff, 30 spline inner/outer axles, heavy duty half shafts with the big 1480 series U-joints. The only thing more you can get from Tom's is a 12 bolt rear stuffed into the 10 bolt case and maybe some more Posi options. In my case this all may have been overkill as I probably won't ever spend much time with slicks. I have only put about 500 miles on this setup but the stuff from Van Steel looks great and very beefy. I highly recommend it. My decsion was based on a feeling that I only wanted to do this once. If I can offer any further help, just ask. Bill.

MotorHead

Even though I believe if you have a rear end in good shape and you will loose traction with street tires I would not forgo a rear end beef up. Constant stress on parts will sooner or later bend or break something. I am going to beef my rear end up in near future just in case.

plainswolf

Wow you're sure putting down some healthy #'s!!

I would agree with others as far as the tires frying first, however if slicks were used then things change.

I do know one thing though, after dealing with very high HP/TQ SBC transplants in early 70's Datsun Zcars, which also have an IRS setup, and squat hard on launch, that U-joints can only handle about 8 degrees of angularity after which, any relaiblity is seriously compromised.

If a Dana 44 with an 8.5 inch ring gear is able to handle it, that leaves the Ujoints, halfshafts, and stub-axles as potential weak points.

But on that same note, there is one guy that runs a highly modified Buick GN engine in his 240Z who switched to a corvette Dana 44 IRS setup in his car, and he is putting down SERIOUS HP/TQ numbers that are right up there with the numbers of your 406. He's been using that setup for at least a few years now and he regularly races it hard.

gkull

I have 79. The iron case with the chevy 8 3/4 is realy a nice unit when combined with custom hardened steel yokes. they sell for about $225 each. I've had mine for about 12 years with 4.11 richmond rear gears.

The weak link is the posi unit. I have toms about $700 posi units. I also have custom half shafts nice U-joints HD trailing arms......... even with the best u-joints they seem to go

I'm only at the mid 500 hp level. I've been able to do over the years 100's passes with 10 -10.5 slickes with my 3500 stall and years of road racing with 1000's of bad miles

Jim has a 12 bolt IRS behind his 540 ci. Thats the next level when your talking 700-800 RWHP Norval has a blown 468 in the same power range and has his custom spindles that are a work of art.