63 BW T-10 Transmission Clutch Problem

[Larry Stewart]

I feel like I need to go back to basic 101 again but I'll ask the question anyway. Transmision was starting to grind going from 1st to 2nd....then over a period of time it started from 2nd to 3rd then to 4th (I bypassed 2nd when this started to happen). So I thought the syncros were going so pulled the tranmission out, go a rebuild kit from my wife for Christmas, and just pulled the side cover off this weekend and did a visual inspection of the inside. Everything looks great...no shavings...no missing or ground teeth on syncros, and the gears, sliders, etc., look great also.

Now the question, was the solution all along just to adjust the clutch rod? Or even though the tranmission gears look good the syncros could still be bad?

Appreciate any thoughts....feeling stupid in VA.

...Larry...

[Wayne W.]

Re: 63 BW T-10 Transmission Clutch Problem

Your definition of grinding and mine may be different, but if you are talking about a clashing as the syncros are engageing as the shift occures then its probably the syncros. If the grinding continues to occur after the shift or when the clutch is engaged in neutral then its probably the counter shaft bearings or the mainshaft bearings. Neither of these would be evident from visual inspection.

[Joe L.]

Re: 63 BW T-10 Transmission Clutch Problem

Larry----

It can be very difficult to assess the condition of transmission synchronizers by simply removing the side cover. That's because there are many relatively subtle things that can be deficient and worn blocking (synchro) rings are just one of them.

First off, of course, are possible problems with the blocking rings. This can include rounding of the "teeth". You may need to examine the teeth very carefully with a magnifying glass to ascertain their true condition. Also, blocking rings do crack. This is usually impossible to see with the transmission assembled. In fact, the best(and sometimes only) way to check for this condition is to remove the rings from the transmission and carefully "drop" them on a hard surface. If they make a "ringing" sound, they're usually not cracked. If they make a dull "thud", they're cracked and useless.

Second, the synchronizer assemblies, themselves, may be worn or broken. The teeth on the "slider" section of the assembly are susceptible to wear. Also, the three plates, often called "dogs", which are critical to proper functioning of the assembly may be worn.

Lastly, the syncronizer engagement teeth of each gear may be worn. These small teeth on the ends of the gears are the most critical and wear-prone part of the gears. Often, I see folks inspecting gears by simply looking at the main teeth. The main teeth of a gear are are probably the part of the gear which is LEAST susceptible to damage; Muncies and T-10s are constant mesh types of transmissions(except reverse) so there can be no damage as result of "gear clash". The small synchro engagement teeth CAN AND OFTEN ARE DAMAGED/WORN. If these teeth are seriously rounded or worn, synchronizer problems will result. They can be "restored" to some degree using a Dremel or other grinding tool to restore the "v" shape of the teeth. The problem is that when this is done, the material removed usually gets down through the surface hardening. Then, the teeth will re-wear very quickly.

[Larry Stewart]

Re: 63 BW T-10 Transmission Clutch Problem

Joe, I was hoping you would weigh in on this. Thank you both for your suggestion...I'll go ahead and take it over a friends house (who has the press) and rebuild it, especially since I already have a new rebuild kit. It was just one of those things you ask...did I only need to adjust the clutch. The transmission was rebuilt about two years ago when I picked it up in CA and I have only driven the car approx 6K since then. Appreciate the info and will proceed to rebuild...good learning experience anyway!

[Duke W.]

Re: 63 BW T-10 Transmission Clutch Problem

Gear clash can be caused by a dragging clutch. The freeplay of your clutch pedal should be about one inch with the underdash mechanism set for the standard pedal travel, and about 3/4 inch if it is set for the short travel pedal. Freeplay decreases with clutch wear, so if the freeplay was set properly the last time the clutch was adjusted it should never drag, but whether the clutch was properly adjusted or whether the linkage components are correct and in good working order is unknown to me. The fact that all gear shifts result in clashing indicates to me that there may be a problem with clutch disengagement. Gearbox synchronizers rarely all go at nearly the same time.

I recently drove a ' 63 SWC that was to be given away in a contest and the first thing that I noticed was that it had no freeplay. I corrected this within a couple of minutes as the Corvette has a very simple and easy to access clutch adjustment. I would suggest thoroughly inspecting your clutch linkage to insure that it has the proper parts and everything is in proper working order. Since you have the gearbox out I would suggest removing the clutch and verifying all clutch parts are correct for a '63. The '63s have some unique clutch parts which I think include the bellhousing and clutch release fork. On a 35 year old car you never know what's been changed over the years or if replaced parts were correct.

Duke

[Joe L.]

Re: 63 BW T-10 Transmission Clutch Problem

Duke and Larry-----

Yes, I didn't intend to imply by by previous post that I felt that the transmission was the source of the problem; I think that there's a VERY good chance that clutch adjustment could be the problem. However, with the transmission already out of the car and a rebuild kit in hand, now might be a could time to rebuild the trans and INSPECT it carefully in order to rule out the possibility of a trans problem. I really can't see re-installing it as-is only to possibly find out that clutch adjustment wasn't the problem.

Clutch adjustments on C2 and C3 Corvettes can be tricky. That's because, quite often, when you have the specified amount of FREE-PLAY, you will not obtain full clutch dis-engagement at maximum pedal deflection. That's the condition that can cause a transmission to grind when the clutch is fully depressed. If this happens, the only alternative is to reduce the amount of free-play so that full disengagement is obtained at maximum pedal deflection. Hopefully, this condition can be obatined before the FREE-PLAY is reduced to zero. Achieving full clutch disengagement at maximum pedal deflection is more important than achieving the specified measurement of free-play, but some free play is necessary, too, or the clutch will likely slip in the engaged position and release bearing life will be short.

[Rob Brainard]

Re: 63 BW T-10 Transmission Clutch Problem

Larry, One thing not asked of you was - do you have a difficult time getting into reverse? If not then I would say you do not have a clutch problem as this means the input shaft is stopping and therefore the clutch is disengaging. While you have a rebuild kit for the T10, I find it strange that you must rebuild it after only 6K. Either it wasn't rebuilt when you got it or you do an awful lot of power shifts.

[Loren L.]

Re: 63 BW T-10 Transmission Clutch Problem

To go to your basic question, "PERHAPS" clutch adjustment was enough. To deal with where you are NOW, do the synchros and the bearings AND replace the pressure plate, throwout bearing and clutch disc - make it so that you NEVER have to do this again.

[Duke W.]

P.S.

Also be certain that you have the correct and compatible parts. According to my Chevrolet Corvette Parts Catalog (rev. 9-77), the '63 clutch housing ( ID 3788421) is common to mid year small blocks, but the '63 has a UNIQUE clutch fork (3820008). The release bearing (908120), 1 1/4 inches long, was a used from '55 (second design) all the way through through '63, but then CHANGED beginning in '64 to a 1 7/32 long bearing (908093) along with a new fork (3887177). The key here is that you have to have the right fork/bearing combination, but I looks like either one will work. Make sure you have the right combination and they are not mismatched. My statement that the '63 clutch housing is unique was incorrect. It is the '63 FORK that is unique when used with the original length bearing.

Duke

[Joe L.]

Re: P.S.

Duke-----

The principal difference between the 63 clutch fork, GM #3820008, and the 64-81 clutch fork, GM #3887177, is the configuration of the push rod attachment. 1963 uses a stamped socket into which a "ball stud" type push rod end articulates. This same system was used on many other Chevrolet cars of the 60s period. The 64-81 fork uses a clevis pin and retainer to attach the push rod end which, for these years, has an "eyelet" on the clutch fork end. As far as I know, the only requirement for the 63 fork involves the desire to use a 63 push rod and original configuration. Otherwise, by substituting a 64-66 fork push rod, GM # 3844209 and clevis pin GM #3738054, the 64-81 clutch fork can be used on a 1963.

As far as the release bearing goes, the 1-1/4" 55-63 bearing, GM #908120, has been discontinued and replaced by GM #908244, which is also a 1-1/4" long bearing. The 1-7/32" 64+ bearing, GM #908093, has also been discontinued and is replaced by the 1-1/4" long GM #908244 bearing. So, currently, the GM #908244 release bearing SERVICES ALL 55-81 Corvette applications.

[Duke W.]

Re: P.S.

Thanks for illuminating me on the clutch fork, Joe, however, one question, remains, at least for me. What's the consequence of using the 1/32 inch shorter '64 an up release bearing with a '63 fork It may not be much, but assuming 100 pounds pedal force with six inches of travel to release 2600 pounds of clutch clamping force, the total bearing movement would only be about a quarter inch. The shorter bearing would put the initial adjustment further down the thread on the pedal push rod, which would be okay, I suppose, as long as you doesn't run run to the end before the disk is worn out. Do you you of anyone else know of any consequences if the '64 "short" bearing is used with a '63 fork.

Duke

[Larry Stewart]

Thanks for all the advise!!!

Rob.....no problems going into reverse at all. I do no power shifting and yes the transmission was purchased two years ago and was supposed to be rebuilt at the time....had no reason to doubt it since the individual was an NCRS member and came highly recommended. I'm in Charleston right now on travel but will do a good inspection of the clutch assembly when I return. If no indication of any problems exist there will go ahead and rebuild the transmission.....this is turing out to be a really good learning experience for me also.

Appreciate all the comments and help.

...Larry...

[Joe L.]

Re: P.S.

Duke----

The 63 Corvette originally used the 1-1/4" release bearing and that's also the same length as the replacement available today. I don't think that using the 1-7/32" long bearing in a 63 is much of an issue since you can't buy that bearing anymore.

The real issue, and perhaps what you meant, was what's the effect of using the 1/32" longer replacement bearing in 64+ Corvtte applications? I believe that the potential problems which you described are a very real possibility. In fact, I believe that's why folks have such a difficult time getting the clutch on 64-81s adjusted properly. That 1/32" difference is enough to create adjustment difficulty. As I've said many times before, trying to achieve the specified pedal free play AND achieving full clutch disengagement at maximum pedal deflection can be very challenging. Not for me, though; I've got 3 of the original 1-7/32" bearings in my collection so I'm set for life.

[Wayne M.]

[Martin M.]

Re: P.S.

HI:

Just for the record, there are 2 421 bellhousings used in '63. The T10 clutch gear bearing retainer is about 1/2 inch larger than the Muncie, and as a result the 421 for the muncie bell was produced with a smaller opening. The Muncie was later changed to the larger size (4 5/8"), and the early '63 bell would then fit. I have examples of each.

Marty