78 Pace Car Questions

[Matthew S.]

I recently bought a 78 Pace Car with 1,100 miles on it. The car is original except for a few small items. Unfortunately some things have suffered from lack of use. I'm looking for some advice on how best to fix these items.

1 - I have an issue with the transmission where the gears grind when downshifting from third to second and also from second to first. The fluid is full and clean but I plan to change it anyway and see if that makes a difference. Any suggestions on what gear oil to use? Are there any additives that might make the gears shift better? I'm also going to check theh linkage adjustment and make sure that's correct.

2 - The sunvisors don't move up and down, they are frozen in place. Any suggestions on how to free them up without breaking the insides?

3 - The passenger side outside mirror is also frozen in place. Is there a way to remove the glass so I can get at the mechanism behind it?

Thanks for your help!!

[John H.]

Re: 78 Pace Car Questions

1 - I have an issue with the transmission where the gears grind when downshifting from third to second and also from second to first. The fluid is full and clean but I plan to change it anyway and see if that makes a difference. Any suggestions on what gear oil to use? Are there any additives that might make the gears shift better? I'm also going to check theh linkage adjustment and make sure that's correct.

Matt -

First thing I'd do is check the clutch adjustment - you should have 1" to 1-1/4" of pedal free play at the top of pedal travel before you feel any resistance when depressing the pedal.

Any brand-name 75W90 gear lube will work fine; you don't need any "miracle" additives or hot-rod lubricants.

[Jim W.]

Re: 78 Pace Car Questions

Have to agree 1000% with John, But if in fact the car has only 1100 miles, it seems odd that it would even need any adjustment at all, Transmissions don't wear out from sitting unused. But . . . Also as advised, a Good top of the line gear lube like 75E/90 is perfect, I only thing I could suggest is you use a synthetic, which would make the future of gear shilfting somewhat more pleasant. You should be able the clutch pedal a good inche before you feel any resistance ! I'd like to ask, Do all the gears shift hard or only the forward gears? If you shilf into reverse, is there any other noises?

[Stuart F.]

Re: 78 Pace Car Questions

I would like to add that some Corvette service shops have been changing the transmission lube on older Vettes and refilling with the light weight lube used in newer year Vettes. I don't know the weights or applications, but that happened to me on my 63 once. I was getting synchro catch when downshifting as well as excess gear noise and thought it was due to my original clutch plate sticking, which is common when the car has sat awhile. I finally decided to change the lube myself to see if that would help, and found the stuff that the service shop put in drained out with the consistency of water. When I refilled with the proper heavy weight gear lube, my problem went away. Only can hope no permanent damage resulted.

My son has owned 3/78 P.C.'s over the past 3 or 4 years, including 2 that he got T.F. with. As I recall, he had frozen visors on all three. He replaced them with aftermarket pieces from A. K. on 2 of the cars, but was never happy with the looks of the replacements. Believe it was the stitching that was incorrect as well as the grain of the material. On his last, and best car, he chose to take the hit on points in order to retain the correct appearance and save the expense. I don't recall whether he had any mirror problems, but other common faults were with the alarms and all of the power antennas. There was also a problem with the windshield wipers on 2 of them where a ground wire attached to a screw on the housing. The screw was too long and stripped out the threads in the plastic housing which made for a poor ground. We found an easy fix by wrapping the screw with a fine piece of brass wire (from a wire brush) to act as a sort of "Heli-coil" so it could be tightened and make a good ground.

I will mention your thread to him and perhaps he will respond. He has sort of earned a rep as the 78 P.C. Guru in many NCRS circles. He has seen many of the maladies of this particular car and dealt with them.

Stu Fox

[Matthew S.]

Re: 78 Pace Car Questions

Thanks for the feedback guys. The transmission shifts fine when up shifting, no problems from first to fourth when accelerating. I only have a problem when downshifting. Reverse is fine too. No gear grinding or other problems. The clutch needed a little adjustment, there wasn't a lot of freeplay but it's OK now.

Stuart - that may be the case. When we checked the fluid a couple of weeks ago it seemed awfully thin to me. I'm hoping that new fluid will solve the problem.

Matt

[Joe L.]

Re: 78 Pace Car Questions

I recently bought a 78 Pace Car with 1,100 miles on it. The car is original except for a few small items. Unfortunately some things have suffered from lack of use. I'm looking for some advice on how best to fix these items.

1 - I have an issue with the transmission where the gears grind when downshifting from third to second and also from second to first. The fluid is full and clean but I plan to change it anyway and see if that makes a difference. Any suggestions on what gear oil to use? Are there any additives that might make the gears shift better? I'm also going to check theh linkage adjustment and make sure that's correct.

2 - The sunvisors don't move up and down, they are frozen in place. Any suggestions on how to free them up without breaking the insides?

3 - The passenger side outside mirror is also frozen in place. Is there a way to remove the glass so I can get at the mechanism behind it?

Thanks for your help!!

Mathew-----

I agree with other responders; I can't imagine how you could have a transmission problem with 1,100 original miles on the car. For that to occur, someone would have had to really "thrash" it for most of those 1,100 miles. One thing you do have going against you here, though, is that 1978 Corvettes with L-48 and 4 speed usually used sort of an "oddball" transmission. It was called a "Muncie" but it was, basically, a warmed-over version of the Saginaw 4 speed used on some late 60's Chevrolet cars with low and medium performance engines. The name changed when its manufacture was transferred from Saginaw Gear to the Muncie, IN transmission plant (where 63-74 Muncie 4 speeds were previously manufactured).

This transmission is not as heavy duty as the T-10 used in 1978 L-82s or the original Muncie 4 speed transmission. You don't even want to need parts for it. You can confirm that's what you have by simply looking at the transmission case. The "Muncie" will have a cast iron case; the T-10 case will be aluminum.

[Oliver B.]

Re: 78 Pace Car Questions

The visors seem to be known to be moved up/down only VERY hard (the ones on my 77 are the same)... Seems to be the way they came from the factory!

As far as I learnt (here from the TDB) it is not a good idea to play around with WD40 or similar, as the basis of the visors is made from cardboard - trying to lube something would result in damaging/destroying them...

[Greg A.]

Re: 78 Pace Car Questions

Matt, I have a '78 Silver Anniversary and it has the same passenger side mirror arrangement. You need to remove the inside door panel and remove the screws that hold the mirror to the door. Once you get it off, you should be able to get inside the "bullet" housing to lube the mechanism.

I had mine apart (twice) a number of years ago and I'm a bit fuzzy on the operation, but could walk you through if necessary. It was a PITA getting the ratchet into the door to unscrew the mirror and I do remember dropping parts inside the door and spending a lot of time fishing them out. The normal issue is that these mirrors get loose. If you do take yours apart, remember to use loctite on re-assembly...I learned that the second time!

Greg.

[Peter G.]

Re: 78 Pace Car Questions

Mathew on the sunvisors..

I found a replacement at Bloomington Gold Swap Meet. It was in good shape just very dirty and it would not move.

I screwed the hinges that would mount on the car into a 2x4 piece of wood so I could work with it. I did use a very small amount of WD-40 and in the right spot down into the chrome arm and it freed up the visor very quickly. Use very little amount and rotate the visor just until it starts to move. You can over lubricate like the above msgs said and saturate the cardboard and make the visor so lose that it won't stay up when not needed.

[Matthew S.]

Re: 78 Pace Car Questions

Thanks for all the feedback.

Joe - I believe the tranny case is cast iron.

Greg - I will take the mirror off and try lubricating the mirror mechanism from underneath. Is the mechanism made from plastic or nylon? What did you use to lubrciate it with and get it moving again?

Peter - I'll check it out and see if I can get the visors off and work with them off the car.

[Oliver B.]

Re: 78 Pace Car Questions

Mathew on the sunvisors..

I found a replacement at Bloomington Gold Swap Meet. It was in good shape just very dirty and it would not move.

I screwed the hinges that would mount on the car into a 2x4 piece of wood so I could work with it. I did use a very small amount of WD-40 and in the right spot down into the chrome arm and it freed up the visor very quickly. Use very little amount and rotate the visor just until it starts to move. You can over lubricate like the above msgs said and saturate the cardboard and make the visor so lose that it won't stay up when not needed.

Where is "the right spot", Peter?

[Peter G.]

Re: 78 Pace Car Questions

Oliver..I just put a squirt down the chrome shaft/arm that the visor is mounted on.

It lubricated it so quickly maybe three turns and from being completely rusted stiff, that anymore movement and lubrication would make it so the visor would not stay up when not in use.

[Tom R.]

Re: 78 Pace Car Questions

Thanks for all the feedback.

Joe - I believe the tranny case is cast iron.

Greg - I will take the mirror off and try lubricating the mirror mechanism from underneath. Is the mechanism made from plastic or nylon? What did you use to lubrciate it with and get it moving again?

Peter - I'll check it out and see if I can get the visors off and work with them off the car.

Some of our "mature" members jumped over the editor when this article was published stating something like it was all wrong...cast irons were only used in the 60's or something like that. Afterward, they read the article and retracted their initial outburst. But here is the definitive word, to date, on 78 four-speeds.

http://www.hunt4cleanair.net/Articles/fourspeeds.pdf

[Roger O.]

Re: 78 Pace Car Questions

Matthew there is a GM test you might want to perform.
Engine idling at normal operating temperature , transmission lever in neutral , clutch engaged (pedal up).
The test : push the clutch pedal to the floor , wait 9 seconds , shift to reverse. No grind or clash should be heard or felt.

[Tom H.]

Re: 78 Pace Car Questions

Tom !

Your article on transmissions is great. Learned something new today ! Nice job !! Thanks !