I have a 79 Ford with a one piece slip yoke driveshaft. The driveshaft is stock and I send it out to be re-balanced already. I was told that it was pretty long and the place refined the balance a bit too.

Here is what the problem is: Once you get above a certain speed, over 80 you get a terrible shake in the drivetrain... the hurst floor shifter is buzzing like a be... its terrible.

The shop told me because the shaft was long and that I should consider an aluminum one, which is of course more money.

I also noticed that the slip yoke is what I would call a little loose on the mainshaft of the 303 in the truck.

I know I have a problem. I may need to have that aluminum shaft made, but I am also worried that my transmission's tailshaft might need something too.

Was this a common problem with these long driveshafts? Any of you guys encountered it?

 

someone had this same issue not too long ago on here, he replaced the yokes, u-joints, put in an aluminum shaft but for the life of me i cant remember what the problem was. But at highspeed he said he was similiar issues.

 

I had to have a new drive shaft made, because mine became allergic to my truck and just left one day while getting off the interstate (it disappeared on the exit ramp with a LOUD pop...I think mine ended up costing right around $300, I still had the slip joint, and they supplied me with a new universal joint and rear yoke...it took the guy less than 30 minutes to make it and balance it...it is aluminum, and works great.

I would say if you are getting vibrations already, that you should get it replaced while you can still drive it to the shop...keep the one you have as an emergency spare...it's always good to have a back up...

 

A loose slip yoke could be your problem. If you are lucky (I'm usually not), a new slip yoke could be all you need. If you can find another one, preferrably a new one not a junk yard one, you could pull the old one out and slip the new one on and see what kind of slop it has. If it is tight, your tailshaft on the trans should be ok. I would assume that the tailshaft is made of harder material than the yoke, so the wear SHOULD be on the yoke and not the tailshaft. A dang driveline vibration can drive a guy NUTS..........

 

Thanks guys..... I guess I should get the guy at the shop to give me the new slip yoke first so I can see if it works before I get a new shaft made....

 

My 76 has 3 shafts, 2 to the rear and one for the front axle. I was getting a severe vibration while in 2 wheel at highway speeds. Both ends of my driveshaft's were shot. Both my slip yolks had a little side to side play in them. The U joints fit loosely in the solid yolks even. I had the slip yolks, both male and female pieces, and and the solid yolks cut off and replaced\balanced on both ends of both shaft's and my truck rides rides like new. If your shop stated a balanced steel drive shaft was your vibration problem, and recomended an aluminum drive shaft as the fix, that shop need's fired, well, at least educated/calibrated If there is any side to side play in your slip yoke, both parts need replaced. Just like a U joint, you want it tight, no play. The new slip yolk comes with a hard teflon\plastic? coating on the splines. Make sure you lube it well. As far as taking a junk yard\used yolk to match your shaft, dont do it. The wear patterns are different and if it does work, it is only temporary. Like installinng a new cam with used lifters.

PS The driveline shop re-used my original steel shaft's and I saved $$. I think I paid less than $175.00 a shaft. I'm not sure of the cost of a total aluminum shaft replacement. And if the shop sells you the female spline slip yoke half without warning you of the issues I described, please find another shop. There are true mechanic's\Tech's and "profesional", I use that term loosely, part replacers. TOO many part replacers are out there now...they want ya back...soon

 

I just want to let everybody know where I am.... and thanks for all the advice. I bought this truck from a friend who had the tailshaft of the SROD break off during use. He and I then put in the current 303 three speed with the same shaft, which I how I got the truck when I bought it from him.

When I noticed the vibration I had the shaft re-balanced and re-installed and I was told the shaft need to be re-balanced. It works a lot better, but at higher highway speeds it starts vibrating, and the faster you go the worse it gets.....

I have always beed worried that the bushing in the back of the tailshaft of the 303 is bad, or was made bad because the driveshaft was out of balance..... or maybe the splines inside of my yoke are worn too....

I bought a new yoke and am going to see if that fits the transmission with a lot less play....... and take it from there.....

 

This may or may not be relative to your vibration problem but Ford has on some configurations installed harmonic dampers on the ttransmission tail shafts and on the rear of the cab, yes, rear of the cab. I had a 79 F250 with the long one piece drive shaft and it had one of those devices but I can not remember which one. It could have had both, 30 years is a long time to remember. I've seen the tail shaft devices on other applications but the cab block was new to me. So I would look for one or more of those devices. Does your truck have the original cab or has the truck had any modifications? Perhaps numberdummy or someone else will be familiar with what I write. Good luck. Vibrations are not fun, this coming from an old helicopter crew chief.

 

I have no idea how original it is.... it had dual tanks, but never had a factory dual tank switch or wiring, it is all owner installed, and previously to when my friend got it.....

 

did you lift or lower the truck? may want to check the driveline angle found when it installed my gearvenders over drive it changed the rear end angle [had to cut the shaft 14"] i took to a driveline shop and they installed shims on the spring pads works good now

 

miottimouse.... how do I do this? What am i looking for when I check the angle?

 

Here's a good link to some very good info on driveline phasing and angles. Hope it helps.............
DRIVE LINE PHASING

 

I have some new information. I took my 79 on the highway again and spun it up... and the vibration really come in when I am over a certain RPM and let off the gas..... and the the rattle really come in with the floor shifter....

 

The faster I was going.... the faster I get off the gas.... the worse the vibration is....

 

bad slip joint they are made to break before the tail shaft
sounds worn to me