The Stovebolt Site Forums The Shop Area Driveline Transmission shifting problem

The ‘46 Chevy 1/2 Ton 3 speed transmission was rebuilt about 30 years ago by a shop used by PO. It was installed in the truck, but never used since. He passed soon after the engine and tranny were rebuilt and he’d only begun to reassemble the body. I bought the project from his widow about 8 years ago, mostly in pieces. Since then I’ve had to redo most of the previous effort. Today, I attempted to take Sparky on its first drive since the late 80’s. This is a stock rebuild.

Previous engine starts indicated the clutch needed adjustment. Despite multiple attempts at doing so the tranny cannot be shifted into gear and it grinds when attempted.

Need some ideas on where to start figuring this out. I know virtually nothing about this, but imagine that will be changing soon.

Thanks in advance.

It sounds to me like the clutch for some reason isn't disengaging. If you crawl under there and remove the shroud (and really there should be two but occasionally the vertical one may be missing), you can have somebody push in on the pedal while you watch and you should be able to see the pressure plate pull away from the clutch plate leaving it relatively free to move. Or another test: Can you put on the parking brake, put the transmission in first gear, push in on the clutch and then start the engine? Does it feel like the truck wants to travel? Important note: be ready to kill the engine if the truck starts moving. This is the least safe of the two options I've given you. There may be others, but at any rate I would say your clutch isn't letting go...

I've rebuilt these transmissions, too. They were very simple gearboxes compared to some later ones. Usually I found problems with first gear (people impatiently trying to force it into gear coming back from second gear or using first as a downhill engine brake...that always caused odd gear wear patterns and ruined rollers), always with the roller bearings, sometimes with reverse and that was about it. First was not synchronized as you probably remember but if the clutch lets go, it will usually go into first without trouble. Going into second before putting it in first will usually stop things from spinning as much.
Jon

Will it go in gear w/o the motor running? If it does you may have a clutch disk rusted to the flywheel so it won’t release. Fairly easy fix if you have a helper. Let us know.

Jon posted while I was typing (one finger method). But, what he said.

Thanks guys!
I’ll give Jon’s suggestions a shot.
It will shift gears without the engine running. Is there a simple way to test the rust option?

With the engine off put it in 2nd and push in on the clutch as you push the starter down. If the truck tries to move forward the plate is stuck to the flywheel.

Key off, you don’t want it to start.

Ah thanks Martin. I did away with my foot starter decades ago and don't think about that possibility.
Jon

Like said, clutch disc stuck to plate or flywheel, can also be a stuck pilot bearing / bushing.... Or non-maching components?
J. F.

Thanks again guys. It might be a few days before I can get back on this task. Grandkids Storm and fun about to hit land for the weekend!

Lee check your PMs

Rusted clutch discs are frequently broken loose by driving in high gear. Need to remember how to shift w/o useing the clutch, start in low gear and proceed.

Ed

Block the clutch pedal down with a piece of 2X4 cut to length between the seat frame and the fully depressed pedal, then roll underneath, remove the inspection cover, and drive a putty knife between the clutch disc and the flywheel.
Jerry

You can also free a rusted clutch by towing with the engine off and the tranny in high gear. Hold the clutch pedal down.

46Sparky has tried all the above remedies to no avail. Today with help he pulled the transmission and bellhousing, clutch and plate. No signs of rust. I’m at a loss on which way to point him.

Me too, Martin. Are we certain it is pulling the pressure plate down enough to free the clutch? Short throwout bearing or long? I'm mentally scratching my head here.

Before he puller the transmission, did he happen to crawl under the truck while someone stepped on the clutch pedal to see if a space was created between the clutch disc and the flywheel/pressure plate? He may have just had an issue with the clutch fork ball being worn out, or the clutch fork adjuster was not adjusted properly.

Not sure Carl. I hope he’ll check in here. Did the ‘46 have a choice of long or short throw out bearings?

Thanks again guys!
Yes, as Martin reported we tried all the methods suggested above to get the clutch to engage. None worked, unfortunately. Reluctantly, and with much hope in avoiding, we pulled the transmission. As others have reported that is a chore! After removing and inspecting the cover and spring assembly, clutch plate and disc no rust or obvious reason for malfunction is apparent. The throw out bearing appears to be good, with free movement as expected. That part was apparently used in all 3 speed transmissions from 1938-1950, according to the Master Parts Catalog (1929-1950). It measures 1 7/8” long. It did appear, before transmission disassembly began, to move as needed. The Disc does have a stamp indicating it was rebuilt, which tracks with the transmission having been rebuilt by a vendor used by the previous owner. I am wondering if that might be the wrong part? As may be recalled the truck has not been operated since the tranny and engine were rebuilt sometime around 1990.

We have not inspected the clutch fork ball, but given 52Carls observation, that will be done.

As I indicated in my first post about this I know virtually nothing about this stuff...but that is changing fast! I will also add there is no way I could have gotten this far with the help offered here and a couple of buddies locally.

I am open to any suggestions on how to proceed.

Was clutch disc upside down and the hub rubbing on flywheel bolts?

Good question. We wondered too if that might be the cause. The raised part of the hub points toward the crank, correct?

Yes as I recall the raised part of the hub (little 1.5 inch nipple looking part) faces the flywheel. The proper direction will be marked on the disc or stamped into the hub...frequently it was stamped into the hub.

If there's no rust and the clutch disc is installed the right way and the transmission shaft isn't hanging up in the pilot bushing, and you have the proper throwout bearing and linkage is adjusted correctly it really sounds to me like the pressure plate isn't being compressed enough to release or it has failed. When I was in high school I had a pressure plate fail, but I haven't had this problem since then. When the clutch pedal was depressed not all of the plate would release. The clutch disc would keep spinning consequently. When we removed it, you could see where the ring of spring fingers had been riveted to the pressure plate cover, one side of the assembly was lower than the other side. It had come loose at two of the rivets and it looked similar to this one:

https://tinyurl.com/ycy6auj5

You may have it wrong.. look and see what side looks like it'll have more room at the bolts.
Also possible with a rebuilt clutch that that disc just plain won't fit, could be wrong parts used, or assembled wrong.. just guessing.

In any case you've done a fine job trouble shooting thus far. Don't assume anything is good or right without proving it.

I checked the parts placement sequence and if I understood correctly, the raised (nipple) part faced the crank/flywheel.

I have a spare 3 speed truck tranny and compared the lengths of the transmission main drive gear, the shaft end protruding from the retainer. Measuring the exposed section of the shaft from the retainer base to the end of the shaft there is a difference of 5/32”. The spare shaft is longer by 5/32”. The tranny on Sparky was reported to have been rebuilt at the same time the clutch and engine were done, as indicated previously.

In looking at the Master Parts Catalog (1929-1950), if I understand correctly, it shows the Main Drive Gears were shorter length for 4 Speed tranny’s vs 3 Speed, by 11/32”. I am now wondering if the wrong MDG was installed in Sparky???

Also, I think the possibility the rebuilt disc might be defective is a reasonable guess.

I am considering replacing the disc and maybe disassembling the tranny for a closer look???

Wow, when I stated earlier I’d be learning more about this stuff, I may jinxed myself....

The throw out bearing you removed, was it a long one or short one. If it was the short one and Sparky takes the long one that would explain why the clutch would not release. This is provided both are options on a ‘46. Just throwing stuff at the wall to see if something sticks.🛠

I am uncertain of the required length. This throw out bearing measures 1 7/8” long, which matches the length given in the Jim Carter catalog for 6 cylinder models from 1938-1972. The Master Parts Catalog doesn’t list a length, and only lists one part number, which would seem to indicate there was only one size used. So, I am thinking the bearing isn’t a contributing factor to the problem???

I think the bearing length has to do with the type pressure plate. However it’s been way too long since I messed with one. Maybe some of the other guys that are way more knowledgeable than me will explain it.

1 7/8 is the long one
1 1/4 is the short one

two lengths of throwout bearings for 1938-1957 (1963) to match the different pressure plate designs/domes
http://chevy.oldcarmanualproject.com/1929_57chevyparts/57cmpc0151.htm

Make certain the pressure plate when flat on a table shows all the fingers at the exact same height. If 3 to 5 or more of them sit lower than the others, the thing has failed. All of them at the same height will cause the plate to lift off the clutch disc evenly when the throwout bearing presses against them. If some are collapsed, that part of the plate won't separate cleanly from the disc at the same time. It will lag behind, grabbing the disc when spinning. This is what happened on the one I had fail over 50 years ago. Not common, but it does happen. Just a possibility.

Yes, if the throwout bearing is too short it won't pull the plate far enough off the disc. Same thing will happen. 1 and 7/8 inches sounds about right. I have one of these in the attic, but still too hot to be up there looking.

Jon
I think you are on target! I just measured each of the spring fingers. It looks like 8 of them are from 1/16” to almost 1/8” different in height. That pressure plate also has a stamp indicating it was rebuilt.
I will begin the search for a replacement pressure plate.


If I am understanding correctly the throwout bearing length needs to be 1 7/8”, which is apparently the long version of the two bearings size used. The bearing in hand is 1 7/8”. The other throw out bearing being referenced and shown in later editions of the Master Parts Catalog link appears to be much shorter? I am unable to read the size given in the link for the second bearing size. Is it 1 5/32”? Am I misreading and misunderstanding?

1 7/8 vs 1 1/4

Yes, Sparky. 1 and 7/8" on the nose. I got up in the attic early this morning and fished it out to see. The shorter one for your year...I don't know that but the short one I had to use with the T5 seemed to me to be just over an inch and 1 and 5/32" would probably be right. It caused enough difference in things that I had to make a new clutch linkage rod, but aside from bending a circle that wasn't bad. You can see here:
http://i1154.photobucket.com/albums/p535/JonGoodman/IMG_8524.jpg (the original one)

http://i1154.photobucket.com/albums/p535/JonGoodman/IMG_8522.jpg (the new one which I forgot to take a picture of but is about 3/4 to 1 inch shorter...and it gave me the extra adjustment I needed)

Good luck. We're going to figure this out one way or another. Interesting yours failed the same way. That happened when I was in high school and back then a rebuilt pressure plate was expensive...something like $12.50 as I recall and out where I lived you had to wait while they ordered one from El Paso because they had usually sold the last one they had about 10 minutes before I came in the store.

The PO of my truck had also installed the clutch disc in backwards, it had ground the heads of the fly wheel bolts to where it was difficult to remove them. The protruded portion of the clutch disc points towards the pressure plate not the flywheel and should be clearly marked. Sounds like the pressure plate is out of spec. I would replace everything if it were me. Improperly installed parts that have been sitting assembled together for all those years need to be thrown away. IMHO.

If what I’m reading is correct the long 1 7/8 T/O bearing (like yours) is used on pressure plates that have fingers parallel to the plates surface. The short 1 1/4 bearing goes with plates that have the fingers in a dome formation. Sounds like you’re on the right track. 🛠
Chevys of the 40’s ?

One other item I need to check is the clutch fork. Earlier, I think I recall, it was suggested a pivot ball(?) in or on the fork was referenced as a possible problem. Am I recalling correctly? If so, how is that removed, then reinstalled afterward? Does the fork pry out somehow?

I am about decided to replace the bearing, disc and clutch plate. I need to do some additional searching, but it looks like Jim Carter has the parts listed in their catalog.

Update: For future reference. After posting the question a venture out to the shop revealed the clutch fork prys off with a screw driver and the ball stud that attaches the fork to the bell housing has an 11/16” nut to secure the ball stud to the bell housing.

Rock Auto also has them...both diameters. You can see here:

https://www.rockauto.com/en/catalog/chevrolet,1946,truck,3.5l+217cid+l6,1486452,transmission-manual,clutch+kit,1993

I've done well with LUK parts in the past. They're better than many out there.

The fork snaps on the pivot ball (which unscrews from the bell housing). You can pry it off with a large screwdriver or anything similar. New pivot balls are still sold. I think I bought mine from Rock Auto, actually but that was a few years ago.

I just noticed that LUK set also includes the pilot bearing and a tool to remove it. One way to do that is to pack the thing with wheel bearing grease and with a mallet use that tool to hydraulic it out...old timer's way but it works.

Ok thanks for the info.
I compared the prices between Rock and Carters. For the same parts there is an eye popping price difference! On top of that Rock doesn’t have a core charge with the attendant shipping hassle.
Looks like I’ll be calling in a order to Rock.

I've had very good luck with Rockauto.com. Most of their parts are drop shipped from another supplier but it is still way cheaper.

All the LUK clutch sets I've ever bought are all new and I've had very good luck with Rock Auto also.

I always check Rock Auto first. Another option is Amazon.com. If you know what you're looking for and can be careful to verify parts numbers, descriptions, etc, they've started handling many more auto parts. Amazon actually has the LUK 04-123 clutch kit (the 9 1/8" diameter one) for about $104 and the 10" diameter one (04-003) for about $116. Both prices are higher than Rock Auto, but Amazon Prime will get you free shipping so if you're an Amazon Prime member and the Rock Auto shipping is more than the difference, you could look at that, too. Just another option.

SUCCESS!
We got the LUK kit installed today and the tranny finally shifts smoothly. The kit includes all new parts and does not need a core(s) sent in to Rock Auto. Thanks guys for the suggestion to try Rock Auto for the kit.

The initial problem was the rebuilt clutch disc was the wrong part and apparently 8 of the fingers on the clutch plate were bent differently than the rest. The clutch fork ball stud was removed, cleaned and inspected. It showed no signs of scoring or damage otherwise. It was greased and reinstalled.

Now, I can move on to the next task.

Thanks again for all the helpful advice everyone!

Thanks Lee for the update.