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#2447330 - 02/06/18 09:32 AM 18 spline input shaft diameter ?
moparx Offline
Dreaming of implants

Registered: 09/03/03
Posts: 8961
Loc: north of coder
this is a really stupid question, so please, just consider it from my "old timers" diseased mind ! what is the spline diameter of the 18 spline shaft ? here is the reason for asking. sunday, a buddy showed up with a plastic pilot tool that had 18 splines. however, it was just a tick over 5/8" in diameter, and the pilot was only about 7/16". neither one of us has a transmission, but i said it looked way small, i "thought" it [the spline] should be closer to 1" or so ? i tried the google, but didn't have any luck. so, help this dum old guy out, please ? TIA as always !
beer

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#2447427 - 02/06/18 12:56 PM Re: 18 spline input shaft diameter ? [Re: moparx]
HemiStan Offline
top fuel

Registered: 06/10/04
Posts: 1635
Loc: Virginia
I just measured across the splines of my 18 spine transmission input shaft and across the splines of a plastic 18 spline alignment tool. Both are measuring right about 1 5/32".

Stan

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#2447519 - 02/06/18 03:34 PM Re: 18 spline input shaft diameter ? [Re: moparx]
John_Kunkel Offline
I Live Here

Registered: 01/20/03
Posts: 19458
Loc: Rio Linda, CA
The official input shaft spline dimension is 1-3/16 x 18T.
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#2447601 - 02/06/18 05:36 PM Re: 18 spline input shaft diameter ? [Re: moparx]
it's Bob Offline
enthusiast

Registered: 12/15/04
Posts: 348
Loc: Houston
HemiStan "missed it by that much"....Holding fingers 1/32" apart.



Better than I could measure, probably.


Edited by it's Bob (02/06/18 05:38 PM)

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#2447647 - 02/06/18 06:38 PM Re: 18 spline input shaft diameter ? [Re: it's Bob]
dogdays Offline
I Live Here

Registered: 01/20/03
Posts: 16172
If the splines are the same diametral pitch then the diameter corresponds to number of splines linearly.

If, however, the diametral pitch is changed then you have things like the larger diameter shaft with fewer splines. A prime example of this is on GM and Ford input shafts. A common style is 10 splines. The Ford is 1 1/16" diameter, the GM is 1 1/8", and there are trucks with 10 splines with input shaft 1 3/8". Each example is using a different diametral pitch when they design the splines.

We're luckier when it comes to axles, because MOST of the popular axles use the same diametral pitch. So in general, we know that a 29 spline axle is stronger than a 27 spline and weaker than a 30. This is disregarding the strength of the axle material, of course. However the strength of the axle in torsion increases by the cube of the increase in diameter, so you can see that increasing from a 27 spline to a 31 spline increases strength by 51%.

Had enough?

R.

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#2447679 - 02/06/18 07:09 PM Re: 18 spline input shaft diameter ? [Re: dogdays]
PurpleBeeper Offline
super stock

Registered: 07/05/11
Posts: 753
Loc: Chicago
Originally Posted By dogdays
If the splines are the same diametral pitch then the diameter corresponds to number of splines linearly.

If, however, the diametral pitch is changed then you have things like the larger diameter shaft with fewer splines. A prime example of this is on GM and Ford input shafts. A common style is 10 splines. The Ford is 1 1/16" diameter, the GM is 1 1/8", and there are trucks with 10 splines with input shaft 1 3/8". Each example is using a different diametral pitch when they design the splines.

We're luckier when it comes to axles, because MOST of the popular axles use the same diametral pitch. So in general, we know that a 29 spline axle is stronger than a 27 spline and weaker than a 30. This is disregarding the strength of the axle material, of course. However the strength of the axle in torsion increases by the cube of the increase in diameter, so you can see that increasing from a 27 spline to a 31 spline increases strength by 51%.

Had enough?

R.


Or in other words....some of the Centerforce clutch kits & tools have 18 splines & come up in a search for "70 Road Runner" but are the wrong diameter... ask me how I know.

Another thing to consider is that my eyes aren't good enough to determine the pitch of splines...so I just count them....stupid non-bionic eyes
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#2447683 - 02/06/18 07:11 PM Re: 18 spline input shaft diameter ? [Re: moparx]
135sohc Offline
mopar

Registered: 02/19/12
Posts: 547
Loc: SoMd, USA
The 1990 and older FWD manual transmissions in the K based cars are about 5/8" across and 18 spline input.

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#2447932 - 02/07/18 08:31 AM Re: 18 spline input shaft diameter ? [Re: 135sohc]
moparx Offline
Dreaming of implants

Registered: 09/03/03
Posts: 8961
Loc: north of coder
Originally Posted By 135sohc
The 1990 and older FWD manual transmissions in the K based cars are about 5/8" across and 18 spline input.


i said it was more than likely a front drive tool, but i didn't have a clue what brand or model. thanks john k for the answer ! up
beer

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#2447948 - 02/07/18 09:16 AM Re: 18 spline input shaft diameter ? [Re: moparx]
fourgearsavoy Offline


Registered: 12/07/04
Posts: 9256
Loc: Rittman Ohio
Yeah just type in "18 spline" on E-bay and you come up with lug nuts,boat props,and spindles then a few Mopar related items sprinkled in there laugh2

Gus beer
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