The Stovebolt Site Forums The Shop Area Driveline T5 Input Shaft Question

I’ve been doing a little background work on what I would need to install the early S10 T5 (86 model) I bought a couple years ago…..into my 1951 pickup.

My preference would be skipping the adapter plate to get the shifter as far forward as possible. The 10 spline/21 tooth Jeep shaft is how I assumed I’d do it. However…..

If my clutch needs replacing anyway, is there any good reason to do that? Can I just buy a clutch that matches the S10 spline count and trim the S10 input shaft? I suspect there’s more to it, but I haven’t yet found that specific answer on Lugnutz’s site.

I believe, with the old bellhousings, the shaft needs to be moved 5/8" back from the crank, and that's the function of the adapter plate. If you machine that much off, it doesn't leave that much for pilot duties. Best way to get it all figured out is get a measuring stick and start measuring.

Yes, that's what I did. Since I have an 11 inch clutch/pressure plate, etc I had to hunt a bit but it is all out there. I think I ended up buying a LUK pressure plate, clutch disc and the short throw-out bearing. You can trim the end. I didn't have to since my T5 came from an Astro Van and it was ok on length.

There is plenty of shaft up there to trim, by the way. You can look at the T5 that is for sale currently to see. You may have to trim the front piece to give enough room...I've heard of some folks having to do that but not everyone.

Seems that whatever time or money I save by not swapping input shafts, might be given right back in the oddball clutch stuff I would need.

You can shop and see. I doubt you'll spend more money staying with the stock input shaft but maybe. The thing is unless you just enjoy removing transmissions, replacing the pilot bushing and the TO bearing at the same time you install a new pressure plate and clutch disc is probably a good plan. Shortening the input shaft tip isn't difficult. Remember to carefully file the edges beveled...makes going into the pilot bushing easier and above all make certain the pilot bushing mates well with your input shaft. I've seen folks put new bushings in, never check them and have to re-do that work because the hole was a wee bit too small. But when I did this all the parts were more or less the same price...the challenge was the 11 inch stuff. Just not as much was made for the T5 but as I said it is there if you're willing to look and study. Another suggestion: find a machine shop who knows what they're doing and get your pressure plate re-surfaced...and have them check the run-out. A nice flat pressure plate, a new clutch disk and a new pressure plate will make driving your truck a lot more pleasant. Good luck!

After a bit more poking around, there are at least a few non-specialty options for a decent sized clutch in 14 spline. If you run Rock Auto for a late 80s Astro van, you get a few choices.

With that 14 spline setup, do I need some sort of oddball pilot bushing? Different shaft diameters, I believe.

I looked at LugNutz page a bit more and think I have a better feel for how much trimming is needed on the input shaft and the bearing retainer.

I have a spare 235 engine out in the shed with what appears to be a very newly rebuilt cylinder head. I need so see what it has for a clutch and flywheel. If they happened to be as “nearly new” as the head…I’d be inclined to make the input shaft change and use that 10 spline stuff. If they are not, I’d kinda lean to just running a 14 spline clutch setup.

I think (emphasize that word, please) the clutch disc I got for the 11 inch pressure plate may have fit a Chevy/GMC pickup of some type. There weren't too many to choose from. The pilot bushing...I measured the hole and the shaft and just ordered one to fit. Can't recall where I got it...may have been Rock Auto, actually. It fit just right. You might be just fine with a Jeep input shaft and the 10 spline stuff. The situation I had was that the transmission would fit exactly once I increased the size of the mounting holes just a bit (they were originally metric).

Hold on. I have the answers but need to sit down for a few minutes to post pics and words that make sense. Keep your money in your pocket a few more hours and I’ll post here again. Be patient. I’m at work.

S10 T5 does not always need an adapter plate.
Adapter plate does three things.
1. It spaces the transmission case 5/8” further away from the crankshaft because the S10 factory shaft is 5/8” too long.
2. The 14 splines on the S10 T5 factory input shaft are not cut long enough along the length of the shaft to allow proper clutch disk movement (without an adapter plate). The clutch disk will therefore bind on the shaft and not move away from the flywheel far enough. An adapter plate functionally adds length to the spline travel and solves the binding problem.
3. The 1983—93 S10 T5 transmissions have a Muncie bolt pattern. The 1994—1995 S10 T5 transmissions have a Ford bolt pattern. Sometimes an adapter plate is necessary to allow you to bolt the transmission to your bell housing if there is a bolt pattern mismatch.

The Jeep shaft swap has 3 advantages.
1. The Jeep shaft is stronger than the factory 14 spline shaft. It has a 1.125” diameter instead of 1” diameter.
2. The Jeep shaft has 10 splines just like your Chevy transmission 10 spline shaft. So if you have a functional 10 spline clutch package and flywheel, you can keep that in place. That saves you the cost of a new clutch package.
3. The Jeep shaft has splines that are cut further along the shaft. This allows proper clutch disk movement. Therefore, you do not need an adapter plate if your transmission bolt pattern matches your bell housing bolt pattern. You simply need to trim the tip of the Jeep shaft to achieve the correct length.

There are 2 ways to keep the factory 14 spline shaft and not use an adapter plate.
1. Use a cut wheel to carefully lengthen the splines on the shaft. This takes a steady hand. You don’t want to cut too deep. I think I have a picture showing an example of this. This allows the clutch disk to properly travel along the shaft and move away from the flywheel. You still need to trim the pilot tip and buy a 14 spline clutch disc that will work with your current flywheel and pressure plate. Do NOT cut extra length in the splines if you use an adapter plate.
2. If you buy a 14 spline clutch disc, you can take a die grinder and grind away the rear corners of the splines inside the clutch disc hub. This will allow the clutch hub to travel a little further back on the shaft without needing to cut extra spline length to the S10 14 spline shaft. This allows the clutch disk to move the proper distance away from the flywheel. Do NOT do this if you use an adapter plate.

Lastly, your bell housing must have a 4 + 11/16” center bore to properly index the T5 input shaft bearing retainer. If there is a mismatch in size, you need to use an adapter ring. Often times the adapter plate already has a machined ring to compensate for different sizes. Check with the adapter plate vendor.

Thanks, Lugnutz!

Grinding my own splines sounds like a hassle.

For me, the Jeep shaft is economical. $130 and done as long as the current clutch package is in good shape.
My second preference would be the 14 spline clutch disc. It’s under $100 IIRC but involves work to swap it out. Then use a die grinder to trim the clutch disc hub splines so it can move back off the flywheel properly.
Both will require a trim of the shaft pilot tip.

Lugnutz,
Just wanted to thank you for your T5 build page. Just purchased an 83 T5 for my 3804. Already replaced the 5:13 for 4:11’s. In the rear. Engine was upgraded to a 235.
Jim

Does that T-5 have the .72 overdrive? If so, you are going to be very happy with that 4.11 and the tall tires of the 3800. You will be able to pull stumps and drag them down the road at 70 MPH. 1st gear will be usable as 1st gear instead of a granny gear.

Yes Carl, .72, OD.
The main reason for the swap is lower highway RPM's. Was thinking about doing the swap at Wrenchfest this year but thought twice about it, due to the driveshaft needing to be shortened.
Jim

Jim, I grew up in Montgomery county PA. I’m sure you’ve heard of Souderton.
I’m glad my documentation helped you.
You are very welcome.
Tell us how your truck drives with the new gear box.

Worked in Souderton / Harleysville area for 20years

T 5 - using the stock T 5 W/C = 14 spline input shaft (installed into my 69 Nova , behind my
"stock 250ci L 6 engine" . This IS a 1993 GMC , S-15 , 2.8 V6 , T 5 transmission with the
early front Munice Bolt pattern (trans IS from a 93 truck - - but, was cast in '92 - - thus ,
having the old style front BOLT pattern - "it is a World Class T 5" . And , has the " Electric speedo (VSS) , out-put.
And , I did buy the Jeep 1o spline 'input - shaft' .
I 'DID NOT use' the Jeep in-put shaft .............. I DID use the stock S-15 - 14 spline shaft .
. . I did a search on Summit , and found a = 10.5" dia , 14 spline clutch disc :

on the Summit page - look for : (part # ) ADD - 716104 .

https://www.summitracing.com/parts/add-716104

Then , I DID "Grind my 14 spline input shaft " SPLINES , longer " ; too have more 'movement on
my 'shaft splines' . I did install my T 5 , several times , before I came too this point.

. . # 1. showing how I made my shaft splines LONGER (just like Jay says) .
[img]https://live.staticflickr.com/7811/46833562381_e2f0cea406_k.jpg[/img]IMG_4043 by Jim Partridge, on Flickr

. . #2. With the new clutch disc , on the 14 spline in-put shaft - after, making those splines longer.

[img]https://live.staticflickr.com/4915/45918937735_e72da518b5_k.jpg[/img]

. . I hope this may help "explain , what Jay is talking about" . I still had too "cut off the
in-put 'pilot shaft TIP' . And, cut off the "input shaft Retainer" , cover . - - - I also had a good GM "Saginaw 4sp trans" (too go b- for my measurements) .

Thanks, jim

ps - - I installed my T 5 , back in March 17, 2018 . It has worked very good. And, still using the
S-15 stock shifter.
I have (just 2months ago) = bought another 1993 S-10 - T 5 tranny - - This T 5 , does have the
"Ford Bolt Pattern" - (and has the S-10 shifter "tail-housing location" ) .


and - - - Thank you too " Lugnutz " ; for All your T 5 INFO . . . a great job , Jay .

Jim,
Thanks for sharing the information about the clutch disk. I think that is an excellent choice if you decide to keep the 14 spline input shaft.

Another "How Easy it is".

My approach was no spacer. Shorten the input shaft to match the original SM420 shaft length. Same with the input shaft housing. Use a Dewalt angle grinder to lengthen the clutch splines in the input shaft. Then I took the input shaft to the bench grinder and removed input shaft material on the transmission side of the shaft splines until the clutch had sufficient travel to work without binding. I know this sounds like a recipe for input shaft failure, but keep in mind we're dealing with a less than 100 hp stock 216 engine (in my truck anyway).

Clutch disk. I used an '88 Astrovan 4.3 clutch purchased from Rock Auto for less than $50.00. It actually measures 10.75". The stock pressure plate works fine .

New throwout bearing.

Drilled out tanny case mounting holes to .5", used stock bolts in top holes and two new bottom bolts 2" long.

That's pretty much my story. The original thread is here.

8 years and 20,000 miles and still happy with the conversion. I did swap T5's to get a better (for me anyway) ratio .72 5th gear.

Good Luck,

RonR

I was resistant to the idea of grinding my own splines, but it’s good to hear some success stories. I had some self doubt about successfully executing that.

I’m a cheapskate, and the last two posts have given me a renewed interest in at least trying it. Worst case scenario, I screw it up, and I go buy the jeep shaft which I would have been buying, regardless. Only loss would be buying a different clutch if it played out that way.

RonR, I’m too lazy to go read your old thread. Did you resurface your flywheel as part of this project?

Consider this.
Rather than cutting extra spline length on the shaft - try modifying the hub of the clutch disc.
Tom Langdon suggested trimming the corners of the clutch disc hub splines. Take a die grinder and trim back the inside diameter corners of the clutch disc hub on the transmission side. That way you don’t weaken the input shaft at all. Trimming the corners of the disc hub won’t require as much detail work. You will need to remove any burrs with a file. I’m thinking a trim of 1/8” would be plenty.

JW, it's always smart to make sure the flywheel is true. However being a cheapskate with many years of farm type wrench turning behind me I did not have the flywheel surfaced. Don't really recall for sure but I likely put a 80 grit sanding disk on an angle grinder and scuffed it till bright and called it good. So far it has been.

The above said, surfacing doesn't cost much and a nice clutch is a treat most don't appreciate.


RonR

Basically just chamfer them back? Is that what you’re describing?

Yes. That’s a better way to say it too!

So the engine side of the clutch disc would still have spline engagement. The rear would not, but relieving the corner would prevent it from binding….

Is that basically the theory here?

If you have an outfit near you that resurfaces flywheels I'd suggest you consider it...especially if you'll be removing it anyhow. The place I use always checks the runout and will let me know if they see cracks or anything else that would cause alarm. They also will check the balance, so when I get it back I have essentially a new one. The difference is often notable...especially the lack of any chatter, etc. I think the last time I had it done they charged me $45 or $50. There used to be a place that would remove your starter gear and turn it over in the service but they closed around 2000. Doing that will make it very close to new again.

The clutch hub splines are roughly 1” front to back. Trimming (chamfering) the rear inside corners by 1/8” still leaves plenty of hub spline for strength. Notice how the input shaft grooves begin to taper as you go towards the gear end. Another way of saying that is the diameter of the shaft starts to taper back to normal as the groove becomes more shallow. It’s the tapered shallow area that prevents the clutch disc from moving any further. So lengthening the splines gets rid of the tapered shallow area and that works fine but chamfering the clutch hub also works and a clutch disc is easier to work on.

I am using the 46 bellhousing for my 261 - T5 tranny combo. which clutch fork is correct? also, where can I get a fork clip?

The clutch fork casting# 838711 is listed as the unit for 1938-46 for ALL Commercial and Utility Trucks. Fork clips are available from a number of different vendors. Jim Carter offers it as Part# ME458. The clip is originally listed as GM# 838987, for numerous GM vehicles from 1931 up through the mid-1980's. Hope this helps.

So, I have now became a T 5 (S-10 / S-15 ) 5speed tranny fan (I really liked this "idea" , ever since I did my install = March 17, 2018 .
I also have a post back on page #2 . . . but, I did my install in my 69 Nova - - where-as in the car ; Most of those have / use the 10.5" dia clutch disc (which I posted that : part number in that post ( stock S-15 , 14 spline , 1" dia shaft , using the 10.5" dia
clutch disc) . It has been a great addition too my car ................. and, the reason for this "up-date post" .
Alot of you guys ; using your trucks , may need the same / similar "clutch parts - - or - - you may need the " Larger 11" dia clutch disc" .
When doing my 'search for a correct part number (that took longer ; than my actual install) - - -
And, this is an "Part Number Up-Date , for using an 11" clutch , for your 11" stock truck flywheels .

Summit Does have those type clutch disc , in the 11" , 14 spline , stock S-10 type up-grades . Part numbers - - - are 'Golden' - - -

https://www.summitracing.com/parts/add-716102?rrec=true

Then, once you have a 'good part number' ; you could buy your clutch disc , from your "perferred vendor" .
Yes , I did alot of searching , for ANY useable clutch part number ; many people said they performed the "swap" , but never listed any good part numbers ............. well - here ya' go .

jim

In case Summit changes their link structure in the future, the brand/part number from Jim above is:

Advanced Adapters: 716102