The Stovebolt Site Forums The Shop Area Driveline Check a Pilot Bearing ?

These postings concern a shifting problem:

https://www.stovebolt.com/ubbthread...2/1950-3600-shifting-problem#Post1581222

One of the suggestions is that the pilot bearing may be bad. I also have a shifting problem. Mine is not nearly as bad as that poster's, and I do not want to hijack his question, so I start this new one.

My transmission, Saginaw 7-bolt cover with overdrive, needs multiple, usually two or three, tries to get it shifted into the forward gears, more so for first. Reverse sometimes grinds at engagement. A check with the driveshaft removed and the clutch pushed in shows there is no drag when I turn the transmission shaft while it is in a gear, so I claim that my clutch is disengaging properly. The engine is off during that check.

Is there a way to check the pilot bearing without removing the transmission?

Thanks!

I'd suggest that you're more likely to have a warped clutch center hub. It doesn't take much twist on a clutch as the transmission is being installed to bend a clutch center, which results in the clutch disc dragging slightly, even with the pedal fully depressed. Unfortunately, the only way to check for that problem is to remove the disc and mount it in a lathe on centers, and check for disc wobble with a dial indicator.
Jerry

Thanks! I may take the transmission out again during the winter. I can add that to my checks.

In March this year you reported that the trany + truck was fine. What happened since then?

Good point. I am happy with what I have, and I am enjoying driving it. I am used to taking two or three tries to get it into a gear, so I don't really think about it. But the grinding while aiming for reverse is more recent and more annoying. Thinking of the work to get the transmission out again gives me a lot of tolerance for these annoyances. I was in my early 20's when I converted to the straight drive version of this transmission. To install it I reached through the opening in the floor, picked the transmission off the garage floor and inserted it. An easy, couple of minute job. I'll turn 70 this year, and the overdrive version of this transmission is much heaver, so removing and reinstalling it is a slow and lot of work project, so I am hesitant to the point of maybe not doing it of taking it out again. However, if I find that I need to change a pilot bearing, then that would change my thought.

I've found that pushing in the clutch, shifting into 2ng gear, and then moving the lever into 1st gear or reverse is the method that produces zero grinding.

Second gear is syncronized but first and reverse are not, so putting the trans in second and then moving to 1st or reverse results in smooth shifting with no grinding.

Is your clutch linkage properly adjusted?
+1 on the shifting into another gear and then moving to 1st.
I have to do that sometimes with my 4 speed M-20.

His truck has a full Syncro 3 speed Saganaw overdrive trans.
It sounds like a clutch problem.
Fred

Thank you all for your further input. As Fred noted, 1st gear is synchronized in this 196(6, 7, 8 or 9) transmission. I am having fun playing with the free wheeling feature and also with having 5 ratios to play with. The forward gears do not grind during shifting. I just cannot get them to engage on the first or second attempt. Even in free wheeling mode (road speed less than overdrive engagement speed) I must rev match to get the shifts done.

I had another truck with a non-syncro 1st. I wait at stops in neutral. It was a no thinking habit for me to go to 3rd then around to 1st.

I checked my records. I installed the pilot bearing during January 2012. I installed this transmission during February 2024. I did not have this problem with the previous transmission (1968 Saginaw 3-speed straight drive,) so I do not rule out that I may have damaged either the clutch disc or the pilot bearing during any of the 3 times I installed this current transmission. It appears the only way to check these items is to take the transmission out again. I'll decide what I will do with that during the winter.

Again, thank you all for your help.

I put the rear wheels on jack stands, started the truck, put it in first gear and held the clutch pedal down with a stick cut to length. With that done the rear wheels did not turn on their own, and I could easily rotate them either way. If that check means anything, then I did not find evidence of the clutch not releasing.

With my overdrive transmission's free wheeling feature, I can shift to any forward gear without releasing the clutch at all. When I'm not accelerating with the pedal, the engine is always at idle when the overdrive is not engaged, so I learn that the transmission drops into gear only when the road speed rev matches engine idle speed. When the overdrive is engaged, I still need two or three stabs to get shifted into a gear. That could also be at rev match speed, but I do not yet know the speed of matching for 2nd OD or for 3rd OD.

Too many words. Sorry, I am not good with them. Also, for now I have time to babble words but no time to take the transmission out.

The synchronizers are new, so my new guess is that maybe they need to be worn in. I'm happy driving the truck and am used to stab, stab, stab for every shift.

Does that seem to be a reasonable idea?

Thanks!

We have a bit of winter weather here in SE VA. We had a couple of inches of snow, so the roads are completely white with salt. Ahead of that I put the truck back on blocks and now have the transmission out again.

To review the advice I have been given above:
1. Poster Guitplayer asks why I am whining now after having reported that I am happy with my installation. Answer: I am still very happy with my overdrive operation. I call this shifting problem a separate issue not related to the overdrive unit.

Edit: This is the link to my OD installation adventure: https://www.stovebolt.com/ubbthreads/ubbthreads.php/topics/1571675/1

2. Posters Hotrod Lincoln and rfstrk suggest a clutch problem. Answer: I am following up on that advice now.

Per Hotrod Lincoln's advice I put the clutch disc between centers. I found 0.035" runout. I call that negligible due to the disc being flexible. However, my friend who I bother when I want use of a lathe, is very much more observant than I am. He noted a ridge on the outer perimeter of the clutch disc, and he noticed scraping on the disc springs. When I bought my clutch kit from my favorite FLAPS, I was told that the 10 inch disc is not available, but a 10-1/2" would work. I was able to install it without finding reason to not be able to, so I was happy. Now I am not happy. My flywheel measures 10-1/4" diameter on the working surface which does explain why my 10-1/2" disc has a ridge. The height of the springs above the disc face measure 3/32". The depth of the flywheel measures 3/16". This measurement shows that there is enough clearance, but the rubbed surfaces show that the allowed movement of the springs exceeds the available clearance.

I think that what I need to ask now is: what is a correct clutch (disc, disc and pressure plate, or kit) and where should I look for it?

Look at the heads of the bolts that hold the flywheel to the crankshaft. If they show polished spots that correspond to the rub marks on the springs, the clutch disc has been installed backwards. The springs should go back into the pressure plate, with little to no projection into the flywheel. It's also possible that the bolt heads on the flywheel attaching bolts are too thick, or the wrong lock washer has been used under the bolts. Those springs shouldn't be touching anything, at any time.
Jerry

To review the advice I have been given above:
1. Poster Guitplayer asks why I am whining now after having reported that I am happy with my installation. Answer: I am still very happy with my overdrive operation. I call this shifting problem a separate issue not related to the overdrive unit.

Ok, never realized you were whining. You reported ALL is well. I guess not. If you put the disc in backwards then I`d check it all.

Robert - After looking at your info above and the attached pictures, I can see by the casting number on the bell housing that it is the original 1950 GMC unit. Is the flywheel also the original to the truck, is it a later one that came on the '58 270?

In 1950, the original standard flywheel and clutch would have been a 9" clutch unit (1/2 ton only), with the 10-3/4" heavy duty unit as an option for 1/2 tons and used on all other truck models. Your measured 10-1/4 flywheel clutch face contact (working) surface makes it sound more like you have the non-heavy duty 9" clutch flywheel. If the machined surface exceeded 10-3/4", that would indicate it's the larger heavy duty flywheel.

I think further answers to these questions will help steer the discussion towards the correct clutch disc setup for your existing equipment.

The truck had a 235 in it when I bought it. The flywheel for that was 4 bolt for 6 volt. When I found the 270 I had the 6 bolt pattern drilled into that flywheel. The clutch may have been original. It was 9 inch. I bought the flywheel that I am using now from a member of oldgmctrucks.com. It is 6 bolt for 12 volt. The listing at my favorite FLAPS showed a 10 inch clutch being original, but his part number had been succeeded by the 10-1/2 inch clutch that I have now.

When I had the current flywheel re-surfaced I discovered it to be very ugly with spider web cracks all around. If I can find the right flywheel, then I may buy a new aftermarket one and get the clutch that fits that.