drive shaft lenght

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On a 65 mustang it would be 48.75"

:lol:

What car are you working on?

There are lengths in the factory parts book.

I did an 8 3/4 swap I to my dart ( from a 7 1/4)

The book said 51.62 (just a number, I don't recall the real number)

I measured the slip yoke C/L with the car sitting on the ground to a fixed point in the trans

After the 8 3/4 was installed I put the slip yoke in to the same dimension, and measured. I got 51.25 (again just the number I recall may not be correct)

I went with 51.5 figured it was a nice compromise.

In hind sight I should have gone with the 51.25.

The old seal did not have the extra extended part. The replacement seal does and under some conditions the lip of the new seal rides up on the tapered part of the slip yoke.

Moral of the story

Get it all assembled, set the car down on all 4s, put the slip yoke in to the correct distance, and measure
 
What make and model car? Would be the same a a 340 4 spd car

108 wheel base Duster, Demon , Barracuda is 48 1/2 .

111 wheel base car Swinger or scamp is 51 1/2

This is at factory ride height with original springs and perches.
 
Your best bet is to measure it for the actual car, too many variables and parts that might have changed over the years.
 
Spend a few minutes and get the measurements and call a place like Strange Engineering. I went by the specs off the internet minus an 1/8” based on my inexperience with measuring driveshaft slip yoke protrusion and had a local shop rebuild my driveshaft to that for a few hundred bucks… but I have +2“ leaf springs and now 6 degree shims correcting pinion angles. It turns out I was wrong on my length… Strange Engineering is now building a driveshaft that is 3/8” longer than what I originally had made (1/4” longer than factory spec). Oh, and this error on my part is costing well over $500 to make right using all new parts, cause I am chasing a driveline vibration above 50 mph… there are way too many factors to guess a number… including what’s the correct slip yoke protrusion. I ended up at 1.25” with my first attempt, which industry standard is 3/4” to 1” max… don’t guess, measure what you have…
 
Wvbuzzmaster said:
Spend a few minutes and get the measurements and call a place like Strange Engineering. I went by the specs off the internet minus an 1/8” based on my inexperience with measuring driveshaft slip yoke protrusion and had a local shop rebuild my driveshaft to that for a few hundred bucks… but I have +2“ leaf springs and now 6 degree shims correcting pinion angles. It turns out I was wrong on my length… Strange Engineering is now building a driveshaft that is 3/8” longer than what I originally had made (1/4” longer than factory spec). Oh, and this error on my part is costing well over $500 to make right using all new parts, cause I am chasing a driveline vibration above 50 mph… there are way too many factors to guess a number… including what’s the correct slip yoke protrusion. I ended up at 1.25” with my first attempt, which industry standard is 3/4” to 1” max… don’t guess, measure what you have…
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My local shop only charged $120 to lengthen my driveshaft when I switched to a manual. I'd recommend a small local shop for a better price. (I know, too late now)
 
72Duster440 said:
My local shop only charged $120 to lengthen my driveshaft when I switched to a manual. I'd recommend a small local shop for a better price. (I know, too late now)
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Ya… local shop was an hour away and they did a great job and did exactly what I wanted… however… I was wrong… and that’s where we are now, and chasing a driveline vibration when everything is new/rebuilt from flex plate to rear tire… and the vibration was there before I started this project. So this time I just opted to include no part of the old driveshaft or slip yoke, and start fresh with correct measurements for correct length, and see what that got me.
This is the kind of thing that can and will screw with your enjoyment of the car later. I took it to a local show this past weekend to show and by the time I got there I parked it in the visiting lot as I was 100% over it after a 20 minute drive…. Did not want to even talk about it… but I still did cause well, it was frustrating. Not to hijack but hoping me sharing my experiences with my build and what I would/am doing different now that it’s actually drivable and scary at speed I want to enjoy… measure for custom fit using all new parts and cross that off the list of places to chase later….
 
I chased vibes in my Jeep for months years ago. It ended up being the downward angle of the engine/trans was too much. My driveshaft angles were where they needed to be, drove me crazy. I ended up raising the rear of the trans about an inch, and then reshimmed the rear axle and everything was good. I hear ya though, took forever to figure it out and didn't want to drive/work on it. Good luck.
 
In the last month I replaced a questionable harmonic damper, reshimmed the rear axle for less pinion angle, checked runout on wheels to make sure axles were straight (they are), and yesterday revisited driveshaft again cause every time I “touch” anything with the driveshaft the issue reduces… or moves up to higher speeds…. We are now up to 50 mph… we used to be anything over 20 mph… length is where I am now… and verified that I got it wrong, so as to get any doubt out I’m not reusing any of it (it’s all 7260 joints anyway) and I have a 340/727/8-3/4 sure grip 3.91 gears. Going to go ahead and step it up to 1350s (conversion cross at diff until I decide how to change a yoke on a crush sleeve unit (another problem for another thread).

But here is where I made it to the “Regret Phase” of the project where I regret reusing anything now that I’m way too many dollars into it already and have an unenjoyable, vibrating pita to sort out… and every question that could pinpoint where to even look is “yes“….

A lot of factors for deciding driveshaft length, U joint needs or wants is another factor. Just cause you have a good part doesn’t mean you should reuse it for your build, might be fine, but may not be preferable in the future direction your build goes.
 
I also went to a 1350 setup with a conversion joint out back. I bought the yoke and crush sleeve eliminator from Dr Diff, just have to find time to tear into it.

Stupid question, tire balance? I had Belle Tire balance mine and got a big vibration at higher speeds. Went to a different shop and it turned put they were 3 ounces out of balance from Belle Tire.
 
I will know the tire balance question later this week probably. Tires and wheels are new and balanced 3 years ago and only up to around 100 miles of use so far. I bought new rear wheels due to picking the wrong backspace the rears sit in too far for my liking… by an inch, so will have new wheels and move the tires over later this week and then drive to see. It is possible, I am in Regret Phase still, so everything has been considered and rarely ruled out. I am thinking the vibration predates the wheels and tires too… the build has been going on almost 3 years…

I rebuilt the diff all new except for the 7260 yoke and used the crush sleeve…

Also I would like to not accidentally hijack this thread lol.
 
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