Clearance for 1 piece driveshaft on LWB

[Tiger Joe]

Just did a tremec trans swap in my 67 long bed. I have to get a new driveshaft and was hoping maybe to go to a one piece. I searched and people have done it, but I don't see anyone saying how much clearance you need between the carrier bearing crossmember and the driveshaft. Or at least how much people have and if the shaft ever hit.

The local driveshaft shop recommended a 3.5" aluminum shaft for my truck. It's lowered and I just installed the CPP crossmember. My measurements say with a 3.5" shaft I would have right about 1/2" clearance. Doesn't seem like enough to me. Really don't want to back up my brand new crossmember.

Shop was worried about the length but did caution me I would need to make sure the driveshaft didn't hit the crossmember as one snack would likely ruin the $500 shaft

[Clavo106]

I would think some one with drag racing experience can answer this question since they run safety loops on there drive lines.. the longer the shaft the more flex.. thats the reason for a two piece shaft with a carrier....

[Tiger Joe]

I can't edit my post from last night but shop was NOT worried about the length, but cautioned about hitting it off something and ruining it

[Ironangel]

The reason(s) GM used a two piece drive line are (1) Pinon angle. (2) A two piece drive shaft is stronger and will spin up more rpm before reaching maxium critical speed. They each have their pros and cons but the two piece pro's far outweigh the one piece cons of less weight and rotaing mass. A one piece shaft will deliver more instantainious response, but with more stress to the slip yoke and tail shaft bearing in the transmission as well as the pinon bearing(s) in the differential. For the cost of an aluminum shaft with an aftermarket crossmember, I could buy a case of carrier bearings and never worry about critical speeds or vibrations wiping out a bearing. Your shaft shop is correct to warn againt contact or strikes to the aluminum shaft because one slow hit on a speed bump or a racoon at 70 mph will do it in. Do some research, most all muscle cars and trucks, domestic and foreign, have two piece drive lines.~Ghostrider~

[Grumpy old man]

most all muscle cars have 2 piece driveshafts ??? Which ones ? I don't remember ANY muscle car using a 2 piece drive shaft with a carrier bearing midline ?
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[67 chevelle]

I think you just need your stock shaft shortened [don't let it go to your head] , that's what I did with mine , frame cut and stock 4 speed to 2004r , cost me 100 bucks

[Tiger Joe]

doing some math on my notepad at my desk here this morning.

If I only have 1/2" clearance at the carrier bearing cross member (which is just over 1/3 of the way from the trans to the rear tires) that would basically mean my rear end can only move down 1.5" till the shaft hits. doesn't seem like enough to me

[Grumpy old man]

It's not enough clearance . $500.00 is a lot of $ for a drive shaft . 2 piece shafts were used just for this reason , Clearance! Unless you start making more room ( cutting the crossmember ) your not running a 1 piece shaft . Some parts just aren't made to work together without modification .
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[Tiger Joe]

yup kinda what I figured not enough room.

I'll probably just have him shorten my stock 2 piece and hope it lasts.

Im running it behind my 600hp 496 BBC.

Edit: ya I wasn't too impressed with the $500 price, BUT he is the closest driveshop to me, less than 15 min away. otherwise I have to drive like an hour.

[NC_John]

Originally Posted by Tiger Joe

yup kinda what I figured not enough room.

I'll probably just have him shorten my stock 2 piece and hope it lasts.

Im running it behind my 600hp 496 BBC.

When I put the tremec in my long bed I just had the driveshaft shortened and balanced. Also had these guys

http://www.driveshaftshop.com/

Put solid u-joints in it to make a bit stronger.

I doubt you are hooking up with 600 hp. Mine just spins, even with posi, so at least its easier on parts and I haven't broken anything yet.

[Tiger Joe]

I've snapped a weak u joint in half on a hard 1-2 shift when the truck hooked. Blew the super T-10 apart twice too. I never broken the actual shaft even at 6500 rpm shifts so I think it will live on.

Two piece is shortened and already installed. Shop said there was slop between the two shafts which he fixed, so I should be good to go.

[NC_John]

I remember the guy at the machine shop telling me the two-piece driveshaft was going to be the "fuse" in my setup. My transmission is way overbuilt for my current engine build (had it overbuilt to handle the next few engine stages) and the 12 bolt rear-end should be plenty strong. I have only 350 hp but ought not have any problems until I get some real tires out back instead of the skinny white-line radials.

[stsalvage]

I thought the new DOT law was nothing over 61 or 66 inches.Drive shaft places bare the responsibility if something goes wrong.And most Drive shaft places won't Do it.

You ever seen a drive shaft come undone under a truck i have 1977 1972 longhorn Pogo stick at 55 mph it was not pretty

[Tiger Joe]

Shop said 1 piece shaft was not an issue for the length I wanted in 3.5" aluminum. My issue was my clearance to my trailing arm crossmember.

Never heard of any law for driveshaft length. GM puts some pretty long driveshafts on some of the trucks from the factory nowadays.