Longbed driveshafts
 

To the guys that race longbeds,

What are you using for a driveshaft? I'm having vibration issues with a 3 1/2" mild steel shaft at high speeds and high rpms and am trying to convert back to a HD-style 2-piece shaft. I'm curious as to what everyone else is using.

Thanks in advance!

Re: Longbed driveshafts
 

I run a custom 2 piece on mine.

Re: Longbed driveshafts
 

Thanks for the reply!
I had a local shop build a custom 2-piece for mine, also. It's based on a 2-piece shaft from a 68' C-20, which uses the HD-style carrier bearing.

Have you had any trouble out of your carrier bearing?

Re: Longbed driveshafts
 

No problems yet, my truck is 4 - linked so doesn't have the factory crossmember, actually my truck has no factory crossmembers at all just the frame rails are stock.

So anyway not sure that the steady bearing is even from anything in particular or just a heavy duty universal piece, guy that did the 4 - link had it built. So far the only thing I've ever hurt on it was I ripped apart the trans yoke, it split and ripped apart, went to a chrome moly piece after that, the rest has survived fine so far.

Re: Longbed driveshafts
 

Cool. Glad to hear that it has held up for you. Hopefully mine will do the same.

Thanks again for the input!

Re: Longbed driveshafts
 

pstds carbon fiber 69" long on mine. held a 1.4x 60 ft at 4000 lbs so far. hoping for low 1.3s next year. lifetime replacement warranty, but they aren't cheap.

Re: Longbed driveshafts
 

What carbon fiber shaft did you get? Diameter?

Thanks

Re: Longbed driveshafts
 

I'm pretty sure it's 3.75" give the guys a call and they will hook you up. Received mine in about a week. Light as it gets.

Re: Longbed driveshafts
 

Re: Longbed driveshafts
 

Anybody run an aluminum single piece driveshaft on a long bed? Almost to the point where i need to get a drive shaft made for my 65 long bed. turbo 5.3 ls and 4l80e will be around 550-600 hp at the wheels. Going to leave off the foot brake no transbrake yet

Re: Longbed driveshafts
 

Gotta look at the critical speed for the length, power, and weight. Another reason I went with the carbon fiber was if it breaks, damage will be minimal.

Re: Longbed driveshafts
 

For those of you running a 2 piece driveshaft which type of carrier bearing are you using? The aluminum and poly type that can be bought through ccp? or the wide oem type?
https://westernchassisinc.com/images...erbearingA.png
https://autoplicity.com/content/imag...03398696_0.jpg

Re: Longbed driveshafts
 

I would never use that POS light duty carrier bearing up top. Those are why so many people dislike 2pc driveshafts. I always use the HD carrier bearing on the bottom.

Re: Longbed driveshafts
 

I'm planning on having one made in the next couple weeks. The shop I'm using recommended a 4" alum shaft for my truck. ~71" length.

Re: Longbed driveshafts
 

What is your gearing? I've got a t-56 with a 4.56 rear. 28" tall rear tires. Dyno'd at 590 hp on 87 octane at the flywheel. Haven't had it on a chassis dyno yet (still reassembling the truck).

The Driveshaft Shop (driveshaftshop.com) told me last week, after they suggested it, that a one-piece aluminum driveshaft 69" long at the predicted max rpm (based on 160 mph) would not hold together. They said a carbon fiber probably wouldn't either and I needed a two piece steel. That was mid last week and I still have not heard back from them.

I might call Denny's Driveshaft this week and see what they would put together. The Driveshaft Shop has a good repuation and they are local but i'm not impressed with them right now.

Re: Longbed driveshafts
 

John what max rpm did you use? Predicted rpm at 160 at 1 to 1 or the max you plan to turn your engine? My little calculator shows 8770 in 4th gear and a bit over 7000 in 5th for 160
Jimmy

Re: Longbed driveshafts
 

You have a lot more going for you than i do. Mines just a little mild 402. For now I'm just sticking with the stock 3.08 gear and the 4l80e. After I posted this, I shopped around and found a reputable guy that's gonna build me a steel shaft for about half the cost of the aluminum.

Re: Longbed driveshafts
 

They came up with 8755 rpm. Not sure what calculator they used.

I ran an online calculator I found to figure out theoretical top speed and it was over 240 mph. I think I used a max rpm of 6,500 rpm and even with the 4.56 rear, the double overdrive (0.50 6th gear) sets it up for bonneville. I'd probably need 1,200+ hp to get THAT kind of speed out of this big brick so figured 160 mph was reasonable (if I was stupid enough to try to get going that fast).

Re: Longbed driveshafts
 

I think right now mine is a 403 (6.0 stroker). I've got a stupid amount of money in it but happily, it shows.

Re: Longbed driveshafts
 

I would be looking at pulling gear out to get the drive shaft speed down to 6500 at 160 and that will also help the pinion bearings survive for a long top speed run. It will take a lot of power to get to 160 even with the drag that a truck produces. Then there is the nut factor at speed with the poor aerodynamics and little or no down force.
Jimmy

Re: Longbed driveshafts
 

That gear is way too much fun around town to change out. I just need to get realistic about an anticipated top speed. I doubt I'll ever really get higher than 120 for a few seconds on the interstate. Not sure what it might pull in the 1/4 mile.

thanks

Re: Longbed driveshafts
 

There is always a taller tire.
Jimmy

Re: Longbed driveshafts
 

This, I recently rebuilt the posi and trans and was contemplating a gear swap from 4.11 to 3.42. Tires are cheaper and easier.

I also run a 2 piece with the hd carrier. There isn’t a time I’m driving I don’t abuse my truck. I’ve done 1/8th burnouts, donuts, rolling burnouts on the highway. Nothing wrong with a 2 piece.

Re: Longbed driveshafts
 

I've got Precision in Tampa building me a 2-pc steel driveshaft. They also recommended i upgrade my pinion yoke (as that would be the next weakest link) so I am doing that as well. Should see everything here this week.

When they asked what my top speed would be I said "you tell me what the limit on the shaft is." In reality, the only time the truck will even see triple digits is in the quarter mile and the occasional freeway on-ramp/short burst (just because). I still have to ask Matt what the critical driveshaft speed will be for my setup but whatever it is I'll just use it as my speed limiter.

I've got 20's all around but should be able to get a slightly taller tire out back when these ones get spent (they're still new).

Re: Longbed driveshafts
 

Fit the new 4" steel shaft up this week. It was pretty light, almost seemed like aluminum but wasn't. Im happy with it for $250. They were able to use the stock yoke from the 4l80e and the small'ish 1310 rear joint. Should be fine for my setup. I wont know for a little while till I get it on the road though.

Re: Longbed driveshafts
 

Good to hear! 250 sounds like a good price. 4" shaft fit through the factory cross member okay?

Re: Longbed driveshafts
 

I guess Im not sure which crossmember you're referring to.

https://i.imgur.com/cIUT5PSl.jpg

dont mind the mufflers. Im replacing the other and have to have my crossover pipe rebuilt.

Re: Longbed driveshafts
 

Didn't realize you were on a different rear suspension, I thought you were on a trailing arm set up like on my 65'. This is the cross member i was referring to ....edit, not my truck just a pic found off google
http://image.trucktrend.com/f/315787...ailing_arm.jpg

Re: Longbed driveshafts
 

Well bumping this thread up for the tumble weeds to blow through LOL.

Anyway I'm changing my setup again and will be playing the driveshaft game late in the spring but have already been doing up some research as I knew it was going to be a run around.

New motor will be in the honest 1200hp range N/A, plus will still have my nitrous on it for play if I want, good for up to 200 shot but setting up to run mostly N/A. Going to a SFI case turbo 400 but going to give a long stock tail housing a try to get my driveshaft length down, only downside to that is will have to run a bushing instead of a roller bearing.

I'm thinking that it should run high 8's on motor, going to put in a 4.57 rear gear, and current tires are 32.3" tall, next set will be 33" both listed with a 102" roll out. Motor will spin 8000, if need be, builder figures a guy will be shifting 7800, with convertor slippage and such and a big safety margin I'd say using 7800rpm for critical speed of the driveshaft through the traps should be more than good as doubt I'll ever see close to that unless I drop rear gearing more yet, right now calculating that center to center on the shaft should be ~ 65".

With all that the calls began, all choices and options point to a CF with only one shop claiming a 5" aluminum would work, most CF shaft makers either can't do a 5" or can only handle a 60-61" max tube length. Still waiting on a couple calls/emails back from one place that initially thinks from past projects they could get it done with a 4" CF but are now doing military contracts and won't change tooling for a one off at this point in time, but late spring could be different.

Anyway I look at it unless the 5" aluminum that one place claims would spin 8000 (sounds high to me and the one calculator I found online, do believe it was DOM .125" tubing), will work, I'll be stuck with a custom 5" CF that is rated 8551rpm, with a nice price tag of ~ $2025 plus trans yoke and shipping.


To be continued...…...

Re: Longbed driveshafts
 

Two piece driveshaft with HD carrier bearing and 1350 ujoints.

Re: Longbed driveshafts
 

Wow! It sounds like you're stepping things up quite a bit. Glad to hear that. That should be a lot of fun!
I'm wondering if a custom 2-piece could be built to live behind that combo. I know it adds a couple more possible breakage points, but, if everything is sized correctly, I wonder if that might be a little easier on the wallet. A 2-piece is definitely a bigger pain to work with, but might be a more affordable option.
Again, just throwing an idea out there. Good luck with it, whichever way you go with it.

Re: Longbed driveshafts
 

I already had my chassis guy modify my loop and 4-link crossmember to a fit a 5” carbon fiber shaft. I know price is high, but they are way lighter and a lot easier on the center section and trans if the shaft ever does let go, both of which are pricey too, not to mention risk of coming through back of the cab.

A tougher 2 piece would definitely be a option, farm truck runs one, and I have one now that could be built tougher, but I’m going to bite the bullet and go carbon fiber. Guess we will see if it is a wise investment or not.

Re: Longbed driveshafts
 

You make some good points about the safety aspect of a hd 2-piece. I hadn't thought about the front shaft wacking the back of the cab in the event of breakage in that area. I did install another d.s. loop just behind the trailing arm crossmember for the front of the rear shaft, but that would only contain the front of that shaft in the event of a failure. A 1-piece would definitely eliminate those particular issues. Along with the added bonus of less weight.

Re: Longbed driveshafts
 

There are driveshaft length and diameter formulas on the web. Use them. I was uneducated about driveshafts years ago and found out what critical rpm means on a driveshaft. It cost me a full exhaust and a TH350. Split the trans from front to back. And made a lot of noise at over 120.