Driveshaft length

Engine, Transmission and related drivetrain.
heli006
Posts: 27
Joined: 27 Apr 2014 22:04

Driveshaft length

Postby heli006 » 14 Oct 2017 16:31

Question. I'm getting ready to mount my driveshaft. 1970 Datsun 510 (obviously). S14sr20det with 5 speed. Is there any magic formula for determining how much I need to have it shortened? I.e. Distance from tip of trasmission output shaft to surface of differential input flange. I've slid the transmission end of the shaft onto the output shaft but because it's too long I can't accurately make a mark on the driveshaft where the driveshaft flange would be when shortened. I can guesstimate it allowing for a bit of play the driveshaft should have to slide on the output shaft for drivetrain movement but if there is a known method that would be great to know. I only want to have the driveshaft length done once, know what I mean? Any help is of course much appreciated!

datzenmike
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Re: Driveshaft length

Postby datzenmike » 14 Oct 2017 17:16

Talk to a shop that specializes in drive shaft shortening not just a garage. I don't know but would guess from the center line of the rear U joint to the outer case of the transmission. They will know how much to move the front U joint back so you have a proper amount of spline engagement yet have some slip for engine and differential movement when accelerating and decelerating.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs

heli006
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Joined: 27 Apr 2014 22:04

Re: Driveshaft length

Postby heli006 » 14 Oct 2017 17:45

The driveshaft will be shortened and balanced at a reputable driveline specialty place here. Just have to get the length figured out. Think I'm on the right track now

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okayfine
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Re: Driveshaft length

Postby okayfine » 14 Oct 2017 19:16

Different shops like different measurements. Call your shop and ask how they want the measurement taken.
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson

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icehouse
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Re: Driveshaft length

Postby icehouse » 14 Oct 2017 21:29

I've always done 36 1/2" center of u-joint to center of u-joint with all KA-SR-CA swaps with an R160 or R180 diff. Could always go 36" if you are worried it might be to long.
"People don't like it when shit doesn't match their rule of thumb." Sam

heli006
Posts: 27
Joined: 27 Apr 2014 22:04

Re: Driveshaft length

Postby heli006 » 14 Oct 2017 21:51

That's what I came up with too


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