MaineDoc

I have a 65 300 horse 4 speed with transmission issues. Basically it refuses to downshift to third from fourth. All other shifts are fine. Inspection of the linkage shows no problems. My transmission guy says a common problem is a worn pilot bearing so I want to order one to have on hand when I pull out the transmission. Rock Auto shows several different sizes. What one do I need? My plan is to inspect the bearing when trans out and maybe avoid a teardown of the transmission. If bearing looks OK I'll bite the bullet and get the trans freshened up.

R66

I use the non-metallic bronze pilot bushing. They have been used for years and will tolerate some bell housing / crankshaft / input shaft misalignment where the roller bearing type pilot bearings require the alignment to be right on.
Pay attention to your old pilot bushing when you take it out. Significant wear means you have alignment or trans front bearing problems. Pull the trans side cover and take a look at everything you can see, an experienced trans man might be able to identify problems you don't see. Also drain and flush the trans to see how much metal debris you get out of it.
My experience with the C2 is I don't want to pull the trans again.

MaineDoc

Thanks. I assume that all of the major vendors will carry the right one. Also, I'm going to order an alignment tool. My 65 Muncie should be 10 splines not 26, correct?

R66

I buy the bronze pilot bushing at a local parts store so I can put a magnet on it, i.e., non-magnetic / non-metallic. Some parts shacks sell a bushing that seems to have ferrous material impregnated in the bronze which is not good on the trans input shaft over time.

DansYellow66

National sells 2 pilot bushings the last time I checked. The one you want is the heavy duty one (HD). It's bronze and non-magnetic. I don't recall a worn pilot bushing being an issue in downshifting before - but maybe I just haven't paid attention. There could be some relationship there since 4th gear is on the input and 3rd shares the same syncro slider. I think more than likely the issue will be a worn brass blocker ring or worn engagement teeth on the gear.

wmf62

USUALLY, a wobbly input shaft can cause it to pop out of gear, not a shifting problem

Bill

Powershift

Pilot bushing dimensions are:

ID - 0.592/.594 GM design is 0.594. Trans pilot nose is 0.590 inch
OD - 1.095/1.093 GM design number is 1.094. This provides a few thousands interference fit in the crank.
Length - 0.750

AutoGear sells a nice oillite bushing # 0-127-006. They are a forum sponsor. I would use them.

Another option is Federal-Mogul #PB-656-HD and GM later replacement #10125896. Be sure to check for magnetic, but they should be okay as is.

Put pilot bushing in freezer bag and in freezer overnight before installing to shrink it down. The only way to make sure the final bushing fit is correct is a trial fit with the trans after installing the bushing, or using a dummy OEM Muncie trans input shaft cut-off for ease of handling for both installation and final fit. That is what I use. Then you KNOW the trans will bolt up correctly when you get to this step. The plastic alignment pieces are not suitable to ensure this correct fit............but are probably better than nothing.

Years ago I remember a friend of mine using a cut-off broom handle for his 1969 GTO clutch alignment. But we got it done (we were lucky that day). Not my choice of tools.

Larry

DUB

I agree with 'wmf62' It is more than likely NOT your pilot bushing. Simply because if you stop and think about it and what you wrote.

IF it can downshift from third to second gear...and from second gear to first gear..and knowing that the pilot bushing is still performing the same function when doing this. BUT it will not downshift from fourth to third. There are no magical anomalies taking place to cause the pilot bushing to change its function when preforming this task. So..it is an internal problem in the transmission. I would bet on it.

Now I may be wrong...but if I am wrong..then someone needs to fill me on how the pilot bushing changes what it is doing only when downshifting from fourth to third gear.

DUB

MaineDoc

Powershift

Do not take for granted that the pilot bushing and trans will mate up correctly without using a OEM Muncie input shaft for final alignment. Also mic-ing the pilot bushing before install. Way too many folks (on this forum and not) have assumed a correct installation only to be disappointed when trying to get the last inch of transmission installed into the bell housing.

FWIW.

Larry

DansYellow66

Larry has a very valid point. Those plastic alignment tools only seem to get me close to aligned - but close is not good enough when trying to get a transmission to seat in the disc, bushing and bellhousing register. You might get by if you have the clutch linkage hooked up and someone in the seat to push the clutch in as you are trying to slide it home. But, I would see if someone has an old input shaft you can borrow or maybe look on Ebay for a used one. Mine is loaned out right now to another forum member.

Easy Rhino

You guys confused me with the yellow C2 avatars - I thought the OP was talking to himself, LOL.

Agree that the pilot bushing is most likely not the culprit; however, if you're stuck with pulling the tranny I would definitely replace the pilot and take a hard look at replacing the clutch and pressure plate and resurface the flywheel, but that's just me and I hate doing a job like pulling a tranny twice if I can do it once.

Also agree with the choice of the sintered bronze (oilite) pilot bearing and no others. But mike the old one and the crank and test fit everything.

If your engine, bell housing, and tranny are original, they are likely to line up without having to mike whether they are radially aligned.

Sky65

Please clarify. You said it refuses to "downshift from third to fourth". That is an upshift. Is the problem third to fourth, upshift, or fourth to third, downshift. If it is third to fourth I can see where a severely worn pilot bushing could be the cause. Fourth gear is made onto the input shaft which is supported by the pilot bushing. If fourth is wobbling allot do to a worn bushing the 3/4 slider may not be able to lock onto 4th gear. 3rd gear being on the same shaft as the slider would still align. Not saying that is the problem but the diagnosis makes sense to me. JMHO

Tom

DansYellow66

Made me look. Actually he wrote "it refuses to downshift to third from fourth."

Sky65

Yes. That had always been an upshift to a higher gear in my world. Not a downshift to a lower gear. Same as a shift from 1st to 2nd is an upshift.


Tom

MaineDoc

johngandersonjr

I had a similar problem with my m20. I could not downshift from 3rd to 2nd until the trans was good and warm. Turns out the trans had wear on the 3rd gear engagement teeth and the synchronizer were worn.

Builder said that caused my issue.

DUB

To date... I have yet had a transmission that would not slide in by using the plastic line up tool to center teh clutch disc. I guess I do take a bit of time making sure the disc is centered before I tighten down the pressure plate. M20, M22 , 6 speeds....it does not make a difference.

DUB

skids

Same here.

Powershift

DUB:

As I stated earlier, I have aligned the clutch disc with a cut-off broomstick........but that is not ideal. The main issue I see is not the actual alignment of the disc, but in making certain that the pilot bushing ID will accept the transmission input shaft nose. Too many folks pound in the pilot bushing without checking the fit to the transmission and the ID is either wrong or they have reduced the ID by pounding it into the crank. Using a old trans input shaft gives you exact alignment and also makes sure the pilot bushing ID is good.

But I am sure you know this. Not everyone does.

Larry