65 Driveshaft Length Question - Photo attached

ks65stang · Nov 8, 2010

I need to have my driveshaft cut and have a different yoke welded on the axle end so I can use a large u-joint to match the 9" yoke (I tried to find a adapter u-joint w/ no luck and have given up on this).

I need to know how much clearance is needed from the end of the C4 transmission tail section to the ears of the driveshaft yoke so they do not come in contact during suspension travel. What is too much? I was thinking about 1.5". I have read I need .75"-1" clearance, but is what I read the same clearnace that I'm questioning?

From my measurements, I dont think I even need to cut any lenght out of the current driveshaft, but some day (years from now) I want to upgrade to a T5. Is the T5 longer and should I maybe cut a little shorter than needed now to advoid a driveshaft mod later?

Thank you!

DukeGnarley · Nov 8, 2010

personally, i would just get the drive shaft to match what you have now. do you have a yoke you can use in the transmission? The way I've done it in the past is to slide the yoke all the way into the transmission, then measure from the middle of where the u-joint cap will go down to the same spot on the axle yoke. then measure the other side. Average the two numbers and then subtract an inch.

If you don't have the yoke you plan on using, go down to your drive shaft shop and get one before measuring. Then take it back to them with the measurements and they will put it on the new shaft.

2+2GT · Nov 8, 2010

If the driveshaft can be installed, with no weight on the rear wheels, then you are good to go. Bolting the rear joint in place will give you 1/4" clearance, and when you put weight on the rear wheels, you'll get even more clearance.

The T5 is a tad longer, but the stock driveshaft usually fits. Not always.

horseballz · Nov 8, 2010

The u-joint that you need is not really considered a "conversion" joint, it's simply the other rear joint listed for a 65. Some 65 Mustangs came with a 9" rear from the factory. What kind of car is your 9" out of?
Gene

ks65stang · Nov 8, 2010

I'm using a Lincoln Versallies 9" which originally used a rear disk type driveshaft attachment w/ a slip yoke driveshaft at the trans end. I do not have this driveshaft and I am moding the mustang driveshaft to work w/ a 9" axle yoke I purchased for the versallies rear end. I attempted to find a u-joint that would fit the stock mustang driveshaft end and the 9" axle end, but no luck after several attampts at Napa and O'Reilly, so I'm just having a matching end put on the axle end of the stock driveshaft.

I have the mustang w/ the suspension all bolted in and jack stands under the axle tubes, so the weight of the car is setting on the axle at ride height. Any thoughts on how much clearance I need on the slip yoke (transmission) end?

Thanks!

ks65stang · Nov 8, 2010

DukeGnarley said:
personally, i would just get the drive shaft to match what you have now. do you have a yoke you can use in the transmission? The way I've done it in the past is to slide the yoke all the way into the transmission, then measure from the middle of where the u-joint cap will go down to the same spot on the axle yoke. then measure the other side. Average the two numbers and then subtract an inch.

If you don't have the yoke you plan on using, go down to your drive shaft shop and get one before measuring. Then take it back to them with the measurements and they will put it on the new shaft.

I just re-read this and that makes sense, so your saying about an 1" is workable. Any thoughts on 1.5" (is this too far out of the trans) so I can maybe fit a T5 later w/ maybe no drive shaft mods.

frdnut · Nov 8, 2010

2+2GT said:
If the driveshaft can be installed, with no weight on the rear wheels, then you are good to go. Bolting the rear joint in place will give you 1/4" clearance, and when you put weight on the rear wheels, you'll get even more clearance.

The T5 is a tad longer, but the stock driveshaft usually fits. Not always.

Unless I am not understanding you right you would get less clearance(driveshaft pushes into trans) with wieght on the wheels?

DukeGnarley · Nov 8, 2010

ks65stang said:
I just re-read this and that makes sense, so your saying about an 1" is workable. Any thoughts on 1.5" (is this too far out of the trans) so I can maybe fit a T5 later w/ maybe no drive shaft mods.

1" of clearance is usually fine. I wouldn't be too worried about getting the t5 to fit. Having a drive shaft shortened isn't too expensive ($50-$100 usually). You might be able to go 1.5" if you want to, but it would reduce the amount of spline engagement you have. This is the kind of thing I would talk to a drive shaft shop about, since they are more familiar with how much engagement you really need.

ks65stang · Nov 9, 2010

Thanks all, you have helped me make my decision, gonna stick w/ 1" and discuss w/ the driveshaft shop prior.

PoppyMod · Nov 11, 2010

ks65stang said:
I need to have my driveshaft cut and have a different yoke welded on the axle end so I can use a large u-joint to match the 9" yoke (I tried to find a adapter u-joint w/ no luck and have given up on this).

I need to know how much clearance is needed from the end of the C4 transmission tail section to the ears of the driveshaft yoke so they do not come in contact during suspension travel. What is too much? I was thinking about 1.5". I have read I need .75"-1" clearance, but is what I read the same clearnace that I'm questioning?

From my measurements, I don't think I even need to cut any length out of the current driveshaft, but some day (years from now) I want to upgrade to a T5. Is the T5 longer and should I maybe cut a little shorter than needed now to avoid a driveshaft mod later?

Thank you!

This may help. When I converted from a C4 to a T5 in my 64.5/65, I did not have to shorten my rebuilt OEM DS. There is a measurement to look for and I think it is between 50-51", as measured on-centers of the universal caps. Mine measured 49.75. So, I kept it.

ks65stang · Nov 15, 2010

PoppyMod said:
This may help. When I converted from a C4 to a T5 in my 64.5/65, I did not have to shorten my rebuilt OEM DS. There is a measurement to look for and I think it is between 50-51", as measured on-centers of the universal caps. Mine measured 49.75. So, I kept it.

I decided to go w/ 51" from u-joint center cap to center cap. Thanks for your feedback I really hoping this driveshaft will work w/ a T5 later.......years later at the rate I'm going.

PoppyMod · Nov 15, 2010

ks65stang said:
I decided to go w/ 51" from u-joint center cap to center cap. Thanks for your feedback I really hoping this driveshaft will work w/ a T5 later.......years later at the rate I'm going.

Don't worry, you'll do fine. There is not that much travel in the yoke actually. The arc of the rear only creates about 1/4 to 1/2 " travel within the tranny tail shaft. A stiffer rear suspension will be more toward the .250" of travel.

hotcobra03 · Nov 16, 2010

ujoint

ks65stang said:
I need to have my driveshaft cut and have a different yoke welded on the axle end so I can use a large u-joint to match the 9" yoke (I tried to find a adapter u-joint w/ no luck and have given up on this).

I need to know how much clearance is needed from the end of the C4 transmission tail section to the ears of the driveshaft yoke so they do not come in contact during suspension travel. What is too much? I was thinking about 1.5". I have read I need .75"-1" clearance, but is what I read the same clearnace that I'm questioning?

From my measurements, I dont think I even need to cut any lenght out of the current driveshaft, but some day (years from now) I want to upgrade to a T5. Is the T5 longer and should I maybe cut a little shorter than needed now to advoid a driveshaft mod later?

Thank you!

you need to find out what type of shaft you have now...mechanics or cleveland than cross to spicer 1310

conversion ujoints
Identify Part by Dimension (J300P)

1965 ujoint choices/make and model
The Expert - K350 - Information for driveshafts, u-joints, axles, heavy axles, light axles, Driveline

2+2GT · Nov 16, 2010

frdnut said:
Unless I am not understanding you right you would get less clearance (driveshaft pushes into trans) with weight on the wheels?

No. With the wheels hanging, the yoke is as close to the trans as it gets. As you put weight on the wheels, the yoke slides out of the trans. 1/4" clearance with the wheels hanging is enough.

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