Replacing the clutch on a 1960 GMC, SM-318

[Corts60]

Hey all, I am in the middle of replacing the clutch on my Jimmy and thought I would start up a thread for info for everyone else. I ran into a couple issues so far. Hopefully I'll take care of all the trial and errors so if any other GMC guys are going to do this, they'll have the answers.

I think everyone is aware by now that I run the original 305A V-6 and SM-318 3-speed. I was getting a little chatter when taking off in first or reverse, so that is why I decided to change out the clutch.

Everything came apart nice and easy. I have a one piece driveshaft, that made things easy on that end. Then I removed the transmission from the bellhousing. Now, the bellhousing on the V-6 incorporates the rear engine mounts. There are no tranny mounts on this set-up. To remove the bellhousing would require the removal of the starter, slave cylinder, rear engine mounts and of course the bolts to the block. I opted to leave mine in for now.

I did, however, remove the rear mounts when I saw cracks. Yup, they were both cracked and broken. If you've never seen these type of mounts, they are very different from the other trucks (see pics below). This is where I ran into the first problem. NO ONE makes these mounts anymore. So, I am ordering a set of later model mounts from classic parts (P/N 79-111) that should work. I think jbgroby did the same thing?

So, I'll shut up and start showing pictures:
Here are the mounts in place

And here is one of the mounts by itself


and here is what I am going to replace them with
http://www.classicparts.com/1954-84-...ctinfo/79-111/

[Corts60]

So then I removed the clutch and started comparing the old and new one. There was some major differences in the pressure plates, pilot bearing and throw out bearing. I went back to NAPA and brought the old clutch with me. Luckily the had the right one there (P/N MU1862-1), so I picked that one up. The throw out bearing is still not correct, it is too short. I went to Jolly's website and found the part number for the long throw out bearing. Tomorrow I'll go back to NAPA and see if they can get it for me.

Also, the pilot bearing is not correct. The kit came with a bushing instead of a bearing. The correct bearing is P/N 7109.

Here is a pic of the throw out bearings, you can see how different the original one is compared to the one that came in the kit.

Here was the first pressure plate I picked up next to the OE one

Here is the correct pressure plate

Here is the OE pilot bearing pressed into the flywheel

[Corts60]

Here are some more pics:
OE SM-318 3-speed Muncie

after a little clean up

[Corts60]

Ok, got the rear engine mounts today along with two new u-joints (P/N 369). I went to NAPA and asked to see their motor mount book so I could look for the picture of the mount I knew I wanted. After flipping through the pages, I finally found what I was looking for, P/N 602-1034. Luckily they had two on the shelves and the cost was about $6 and some change.

As you can see, these mounts are completely different looking than the originals but, these will work just fine.

[Corts60]

Ugh...today was a bummer. I got home from work early to get a head start on putting her back together and I am glad I did. It turns out that on the throw out bearing, you need to re-use your old collar and just press on the new bearing (P/N N1181). I installed the new pilot bearing, cleaned up the flywheel and pressed in the new u-joints. I got everything put back to-gether with the exception of the dust cover and drive shaft. As I was trying to adjust the clutch, I noticed that it would not dis-engage fully with the pedal to the floor. After messing around, I figured something was wrong, so I pulled the tranny back out and pulled the clutch. Sure enough the clutch disc was wrong. And it was so obvious! I can't believe I didn't notice it. My original clutch is 11" and I was trying to put in a 12", but that wasn't what was hanging up. The spline hub in the center of the disc was in backwards on the new clutch disc.

So now I have to order a third clutch from NAPA. We'll see what it looks like in two days.

Take a look see:
This pic shows the old clutch (flywheel side) with no raised hub.

This is the new clutch (flywheel side) showing a raised hub

Also, the size differences


The new and old throw out bearing

The throw out bearing collar

[Corts60]

Oh yeah, I forgot about the rear engine mounts. The ones I picked up from NAPA worked perfectly. The only thing was that I had to trim a little off the forward corners so the dust cover would bolt back up.




Also, here is the pilot bearing showing the one I had to order nex to the bushing that came with the kit

[jonzcustomshop]

looks like napa should comp your gas....

[Corts60]

Hell yeah they should. I just got my third clutch today and it's still not right. It's an 11 inch but the hub still sticks out way to far on the flywheel side of the clutch disc......pissing me off.

I have to do some research tonight.

[jonzcustomshop]

we used to have a place here that would re-line your existing clutch... wonder if there is a place like that by you?

[Corts60]

Originally Posted by jonzcustomshop

we used to have a place here that would re-line your existing clutch... wonder if there is a place like that by you?

Yeah I just got word from the guy's on Jolly's site that NOBODY MAKES THIS CLUTCH. Bummer.

So now I am in the process of seeing if there is someone locally or in Portland that will rebuild my old one.

Boy it takes a lot of patience when you own a GMC V-6......

[slorio]

Cort:
Hang in there. You almost have it. I second the recommendation on getting yours relined. I took mine to a place that relines truck parts, and they redid the clutch and pressure plate next day, no problem. Everyone is trying to sell you parts for the Chevies, but as you see, the GMC's are different.

Regards,
Steve
New Orleans

[sixfour4x4]

is your new t/o the same height as the old one?

[Corts60]

The throw out bearing and the pilot bearing are correct now. I had to buy them seperately from the kits and let me tell you they are expensive. The pilot bearing alone is $27!
My only problem now is that I need to get my clutch disc and pressure plate to Ott's Friction Supply in Portland so they can see if they are able to rebuild it for me. Unfortunatelly, I work all week and by the time I get out of work, I would never make it to Portland in time.....Looks like I need a day off.

[chevytrucknut]

Hey Cort, Otts friction redid a '41 International clutch and brakes for me several years ago, I am sure they can help you. The owner is a friend of mine too so let me know if you need any help.Jack

[mikie 1954]

you orderd motter mounts from classic but then you go to napa to get them , what happened ? also it looks like the throughout arm is on passinger side ,i have a 64 GMC that had a v6 in it and it was on driver side , just quris . hope i spelled that right.

[Corts60]

Originally Posted by mikie 1954

you orderd motter mounts from classic but then you go to napa to get them , what happened ? also it looks like the throughout arm is on passinger side ,i have a 64 GMC that had a v6 in it and it was on driver side , just quris . hope i spelled that right.

yeah, the clutch fork is on the pass. side of mine because I have a hydraulic clutch. Your '64 had a mechanical.

As far as the mounts, they were $6 and some change locally versus $10 ea plus shipping through the other companies.....

[protrash64]

I'm fully automatic over here, but nice write up and pics Corts60. Hope you get it rollin' soon. I'll check back in for the finale.

[Corts60]

Update:

OK, did some backyard modifying today. I needed to get her rolling, as she is sitting in my neighbors garage and we have his projects to tend to (I haven't built my garage yet).

So the issue I was having was that the new clutch disc hub was hitting the flywheel hub, not allowing the friction material to touch the flywheel......so....I just ground off the back part of the hub. I did all my measurements (sorry no pics today) and determined that I still have about 1/2" of teeth gripping the input shaft. Now the normal amount of teeth grabbing is about 1". I DON'T plan to keep this clutch in long....just enough to move it out of the garage and back over to my place while we're waiting for my OG one to get rebuilt in Portland and that's a couple weeks away before I can get it down there.

So today I got the new clutch and pressure plate all bolted up, along with the tranny and linkages.

Tomorrow:
Replace the pinion seal on the rear end, install driveshaft and fill gear box up with oil. Then after I finish adjusting the clutch, give her a quick test drive....

Until tomorrow.......

[retodd7711]

Can't you just ship your parts to Portland to get going quicker?
Thanks for all the info in this thread, sorry you had such a b**** of a time getting your parts.

[Corts60]

Well, I'll be in Portland next weekend anyways because my band is playing a show, and since Jack knows the owner I'll just give him the clutch to drop off for me......

[chevytrucknut]

Sounds like a good plan. Where are you playing? Jack

[Corts60]

I'll give you a call this weekend. We are playing at the Kenton Club in NE.

[Chuck78]

how did the ground down clutch hub work in the thing? I'm going through the same trouble now. I was told that some clutch shops could dismantle the clutch and flip the hub around the other way on certain model clutches and they would work. My big dilemna now is that I want to keep my 305 V6, but I need a 5 speed OD trans and I have two Tremecs in my garage for the truck and the 71 Camaro... Now how in the heck do I get a 26 spline clutch to work on this thing! I really like the uniqueness of the 305 V6, and it runs GREAT and has tons of torque to haul and tow with, but the 400 chevy small blocks in my garage get more and more tempting when I run into problems like this... Just had my flywheel resurfaced and don't really want to throw the old clutch disc back on there since it's a little grooved. Thought about taking the standard 11" GM clutch and grinding down the hub a bit. I was afraid that the clutch would want to wobble when disengaged if I did that though. Let me know how this all went for you. I'm needing to tow with mine this weekend, and it's still in pieces with a fresh flywheel waiting.

Thanks

Chuck

[justcuz]

If your worried about wobble have a machine shop cut the hub on a lathe.

[Chuck78]

It's not so much the cut that I'm worried about, although it would need to be really even and balanced, but more so the absence of 1/2" of spline that would have provided a lot of extra anti-wobble stability at speed.
I did find that Hite Parts Exchange/Hite Parts Rebuilders here in town does remanufacture one-off customer pieces and parts of all kinds, and can not only reman my stock clutch, but also do the 11" 26 spline clutch hub flip-flop for me so that I can have something ready for the Tremec swap.

http://www.hiteparts.com