1SLwLS1

iTrader: (6)

I have a choked 408 making 450/475 to the tire. Monster Stage IV clutch, 12 bolt with 3.42s, stocks trans, stock driveshaft, and Nitto 555's.

At the track this past weekend, the driveshaft/u-joint sheared at the differential. It was a 3K dump on bald Nittos with 1-2 seconds rolling warm-up, nothing extreme. I wasn't shooting for 1.7 60', just to get the car out of the hole without bogging.

I had a little fear that the output shaft may have twisted during the carnage. When I went to pull out the stocker last night, it was bitch to get started. Once it got going, it was easy to slide out until the last inch. It then required a little jerk and it popped out.

This worries me. If I replace it with a quality DS, the weak link will be the transmission. I will know tonight when I put my buddy's stock DS in. If the yolk slides in, it must be OK, for now. Of course the resistance could have come from tolerances at the last inch of travel, with the slip yoke hanging down or something causing a bind, but I am a worry wart when it comes to cars, as I am straddling a thin line of reliable vs funds for repairs.

Let me know what ya'll think, as I know *they* recommend to replace it with a 30 spline viper unit once you reach 600 lb-ft ish to the tire, I am at 475 with a 3600# car.

85MikeTPI

iTrader: (9)

Check it real good with the known-good replacement DS. Folks have broken/twisted them with less power.

1SLwLS1

iTrader: (6)

See, I thought I had read a few of these cases, plus my buddy twisted one in a 4K pound truck with drag radials and 400/400 with 3.42 gears, I think. Either way he busted his just like mine, sheared the u-joint at the differential and when he went to remove the DS, the yoke was stuck to the output shaft due to the spline and shaft twisting. Then again, on Tick's site, they recommend the Level Three, including the Viper main shaft, for 600 lb-ft (rear-wheel) or more. I am at a measly 475 lb-ft. next to that 600, BUT I am at 400 lb-ft. at 3K.

So much mis-information as well as many other variables not being taken into account, leads the novice into a corner of confusion, and when it comes to transmission, I am definitely a novice and in my corner, haha.

I will definitely check the play with that yolk tonight. Obviously, I am planning on upgrading the transmission as the next major money move, but would you go to the track again and run it with something like a PST 3.5" aluminum DS, good for 1000 HP, and the stock transmission? Or not until I have the beefier main shaft?

thesource

iTrader: (60)

In my experience, the mainshaft doesn't twist. It is usually the stock yoke on the driveshaft that twist in the inner splines. When this happens, the driveshaft cannot compress like it should and puts the transmission in a bind. This usually cracks the tailhousing and causes failure.

1SLwLS1

iTrader: (6)

Gotcha. Turns out the mainshaft is fine. Used DS slid right on the yoke, BUT the DS is from a car with a 10 bolt, or something, as the u-joint didn't fit in my 12 bolt pinion.

I need to swap it out, anyone know a P/N off the top of their head?

Brief Encounter

iTrader: (6)

Stock to 1350 is a napa part number PUJ 447

1SLwLS1

iTrader: (6)

Thanks, stock being 1310, right?

TDP

iTrader: (23)

You need the conversion u-joint. I think the part number is 447. Basically you are needing a 3R --> 1330 conversion. Or if you have the 1350 yoke, the 3R --> 1350 conversion. I'd recommend buying it from a Spicer dealer. Try searching for Inland Trucks Parts.

Also, I wouldn't worry about doing a Viper output shaft conversion. I would say the stock mainshaft would hold up fine up to 650rwhp. It is actually rare that it would break, so I wouldn't worry about it.

1SLwLS1

iTrader: (6)

Thats good to know. Would carbon fiber drive shafts have a better torsional spring rate vs other materials, such as aluminum or chromoly?

I have an aluminum driveshaft if that makes a difference in the series. I was thinking I needed a 348 conversion joint which is Spicer 1310 to Spicer 1350. http://www.injuneer.com/Strange12.html - Scroll down to specs. Some people are saying 447 and others are saying 348.

TDP

iTrader: (23)

The stock driveshaft uses the "3R" u-joint, which looks very similar to the "1330", but it is different. So you just need to find out for sure which u-joint your 12-bolt has.

1SLwLS1

iTrader: (6)

I know for sure, I have the 1350 on the differential yoke. 3R-Saginaw 44-1344 are all the same joint type, correct? I am getting conflicting information on which u-joint style the stock DS has, 3R/S44/1344 or 1310. You seem pretty adamant about the 1344 while others are the same about 1310. I am confused more than ever, haha.

TDP

iTrader: (23)

I can tell you that the 1310 was never used in an f-body. The only application I've seen it used is in Jeeps. It is tiny.

1SLwLS1

iTrader: (6)

I am leaning that way as well. I am going to pick up the 447 this afternoon.

cabel1

iTrader: (3)

Spend the money on a good yoke. I twisted 2 yokes and snapped 1 tailhousing. I no have a chromemoly, nitrated yoke and it seems to be holding up.

1SLwLS1

iTrader: (6)

447 it is. Of course there were only (2) in Houston. My local Napa was out, Autozone doesn't have a Duralast number for it, Advance sells the Neapco 2-01153, but none in Houston had them and one (1) O'Reilly's had both. The first one they sold me was missing the snap rings and grease zerk. I got home with it to discover they had the S44 part correct, but the other side was probably a 1310 or 1330. It wasn't anywhere near a 1350. Went back and got the right one with snap rings and grease zerk. All is well. Thanks for the help guys.

So, would chromoly be the wisest choice for either an aluminum or carbon fiber DS with stock transmission? If I go aluminum, it will probably be the 3.5" PST. If carbon fiber, I will probably have one custom made with 3" OD versus the standard 3.5". The radius of the rotating mass has more bearing on MOI than weight. With my power goals now and in the future, I would never need the strength of 3.5" carbon fiber drive shaft. I also like the fact of a better torsional spring rate, so I've read anyway.

Brief Encounter

iTrader: (6)

To clarify the U-joint question. The stock U-joint is a Saginaw 44.

1SLwLS1

iTrader: (6)

Yes, someone should put that information in a sticky somewhere, as there are a lot of people that believe the stock yoke is 1310 vs 1344