26 vs 10 spline clutch

[ToddK]

I’ve been looking at the specs for the new TKX transmission, and see that the Ford units are available in either 26 or 10 spline input shafts. I assume the 10 spline is a 1 3/8” shaft, same as in my big input Toploader. The TKX has more options for a 26 spline input. My question is which of the 2 input shafts is better in terms of strength or availability of clutch and bearings?

[blykins]

The 10 spline will be a 1-1/16x10.

The 26 spline will be the strongest.   

[ToddK]

Thanks, that answers my question.

[TomP]

So the 26 spline would use a GM application clutch disc?

Are these trannies available yet?

[Katz427]

I bought a Ram clutch  for my 428. Gave Ram a call, and had the hub changed to 26 spline. Using a long style pressure.plate.

[427Fastback]

The road race gear set TKO 600's are 26 spline input.The std gear set 600"s are 10 spline.Brent supplied me with a 11" 26 spline Mclead disc when I bought the trans..I run long style pressure plates.

[blykins]

Yes, 1-1/8x26 disc.

I would trust that size over a big input size.   

[BattlestarGalactic]

Spline options aren't really an issue.  You can buy any diameter disc with basically any spline so you can mix/match things even if they call it a "chevy" or "mopar" disc.  All the old race Nash boxes are mopar input spline.  I would guess they offer the transmission in either style only for the ease of installation and not having to change the clutch disc when someone wants to upgrade to an OD transmission.

The finer spline is stronger, less tooth deflection due to the short height.  The 26 tooth gives it more surface area to divide the load upon. The tall 10 tooth spline is more apt to bend/twist/break.

Dealing with the Injection/Extrusion molding repair business for 34 yrs, I've seen the OEM changeover from square tooth drive splines to Involute spline drives for the same reason.

[Rory428]

Spline options aren't really an issue.  You can buy any diameter disc with basically any spline so you can mix/match things even if they call it a "chevy" or "mopar" disc.  All the old race Nash boxes are mopar input spline.  I would guess they offer the transmission in either style only for the ease of installation and not having to change the clutch disc when someone wants to upgrade to an OD transmission.

The finer spline is stronger, less tooth deflection due to the short height.  The 26 tooth gives it more surface area to divide the load upon. The tall 10 tooth spline is more apt to bend/twist/break.

Dealing with the Injection/Extrusion molding repair business for 34 yrs, I've seen the OEM changeover from square tooth drive splines to Involute spline drives for the same reason.

That may be Larry, but both my Jericos and current G Force G101A use the 1 3/16x18 MoPar "Hemi" spline inputs. A couple of years ago, I thought that I broke my transmission, as the car stopped accelerating on a run. Had to tow the car back to the pits, and when I tried removing the transmission, it would not pull out without a couple of long prybars. What happened was that the splines in the clutch disc stripped out. May sound kinda sketchy, but I finished the season by drilling out the rivets from an old disc, and installing the splined hub into the disc that had the striped out splines. Rather than try to rivet the "new" hub in, I used a couple of packs of ARP pressure plate bolts with some grade 8 nuts. Worked great the rest of the season, and I still have that disc. I didn`t want to just install a new disc, as that old disc was contoured to the warping of the heat shields. Never seen a 10 spline disc ever clean off the splines like that.

[BattlestarGalactic]

That is the one downfall of a fine spline.  The collective surface is greater, but the engagement height is small and can strip out.  Like a fine thread bolt, it is better, until it fails at some point.

We had a racer this past summer have a similar situation.  He got up to the water box, but as soon as he dumped the clutch the car just sat there.   It had stripped the splines in the disc.  He had never had that happen before(me neither).   I can see it though as if you look at the disc hub, the minor diameter is quite large which again reduces contact surface.  I would guess they do that to increase the strength of the hub spline, keeping the minor diameter large enough to not create stress cracks at small points.  Give and take I suppose.

[Rory428]

Larry, another factor in the stripped disc hub may be due to the thickness of the hub itself. My older McLeod Soft Lok clutches had a thicker splined section, but the last few discs I got, had much thinner hubs. I wonder if McLeod (or Tim Hyatt), installed the shorter splined hubs as used in multi disc clutches, rather than the taller hubs used in the older single discs. I never had any issues with the older discs. The main reason I went with the 18 spline MoPar inputs was so I could use the easier to find, more compact , clutch fork and throwout bearing for a small input Ford. Plus the 18 spline makes for an easier time trying to stab the transmission into the disc, with the finer spline, it just lines up easier.

[BattlestarGalactic]

Interesting though about the hub thickness.  They are pretty thin compared to what you get for any other typical sprung hub clutch.

I guess they are concerned about rotating weight?  Just a though.  I would give up a few added ounces to have a 1/2" thick hub instead of 3/8".  Or whatever the dimension is.   Mines out, ready to go to Chris for tune up.

[Rory428]

Interesting though about the hub thickness.  They are pretty thin compared to what you get for any other typical sprung hub clutch.

I guess they are concerned about rotating weight?  Just a though.  I would give up a few added ounces to have a 1/2" thick hub instead of 3/8".  Or whatever the dimension is.   Mines out, ready to go to Chris for tune up.

Is Chris Tim Hyatts son? Have you had him do clutch work for you before? I used to get Tim to do my stuff when he followed the NHRA National Event circuit, very convenient. I was planning to ship my Soft Lok back to McLeod soon, but now that I am on the East Coast, thats a long trip. Can Chris also recert scattershields like Tim did? I have a McLeod SBF, and a FE Lakewood that both need to be re certified.  As for the splined hub thickness, I wonder if they just decided to use the thinner hubs to reduce part numbers. The dual disc units need the thinner hubs to make room, but after that incident, I would certainly prefer a thicker hub for my single disc clutch.

[BattlestarGalactic]

I'm going up to his place next weekend to drop mine and friends clutch off.  I'm pretty sure he does recert bells, but I can confirm.