4+3 weird shifting problem
Thread Starter
Intermediate
Joined: Nov 2022
Posts: 35
Likes: 6
From: Georgia
4+3 weird shifting problem
When shifting just the 4 speed portion sometimes it will just not shift. Feels like you just hit a hard stop.
when searching for info on it most of the time people say its clutch related or they blame the pilot bearing. Both of which are brand new.
now here is the weird bit it will do this both with the engine off or on, and if you push it up to where it stops and slowly let off the clutch it will slip into gear.
it almost seems like the teeth of the gear perfectly line up in such a way that it blocks it from going into gear which shouldn't be possible.
also Its probably not syncros because it will still do it when I let out the clutch in neutral to manualy synchronize the gears.
help would be appreciated. Thanks.
when searching for info on it most of the time people say its clutch related or they blame the pilot bearing. Both of which are brand new.
now here is the weird bit it will do this both with the engine off or on, and if you push it up to where it stops and slowly let off the clutch it will slip into gear.
it almost seems like the teeth of the gear perfectly line up in such a way that it blocks it from going into gear which shouldn't be possible.
also Its probably not syncros because it will still do it when I let out the clutch in neutral to manualy synchronize the gears.
help would be appreciated. Thanks.
Intermediate
Joined: Nov 2024
Posts: 27
Likes: 1
From: Warsaw, Poland
I have similar problems. When I bought C4, all gears seems to work quite good. I had first trip ca 15km and find out that it is a problem sometimes with 1st and reverse. Then it was ok. Today I wanted to have a ride and I was not able to put reverse. I did it with grinding. Then I was not able to put 1st gear. I started from 2nd. Then seems to be ok, but on first lights I was not able to put any gear. The were blocked. Pushing clutch few times did not helped. Finally I managed to put a gear and back, but it looks that problem is more serious.
Are there symptoms of end of clutch ? Or maybe it is some problem with gear adjustment ?
Thread Starter
Intermediate
Joined: Nov 2022
Posts: 35
Likes: 6
From: Georgia
For me the issue seemed to go away after emptying the gear box filling with kerosene running at idle going though the gears at idle, then filling back with the spec gear oil. Try to find stuff without lsd additive if possible. As for your first gear lockout l think I had that a few times and could get it in gear by slowly letting off the clutch till it lined up. As for your reverse grinding you ought to put it in first gear before putting it in reverse since it’s not synchronized.
oh by the way in my experience a clutch going out lends itself to problems getting moving, not putting in gear. You may want to look at your clutch hydraulics and make sure it’s fully bled
oh by the way in my experience a clutch going out lends itself to problems getting moving, not putting in gear. You may want to look at your clutch hydraulics and make sure it’s fully bled
Intermediate
Joined: Nov 2024
Posts: 27
Likes: 1
From: Warsaw, Poland
For me the issue seemed to go away after emptying the gear box filling with kerosene running at idle going though the gears at idle, then filling back with the spec gear oil. Try to find stuff without lsd additive if possible. As for your first gear lockout l think I had that a few times and could get it in gear by slowly letting off the clutch till it lined up. As for your reverse grinding you ought to put it in first gear before putting it in reverse since it’s not synchronized.
oh by the way in my experience a clutch going out lends itself to problems getting moving, not putting in gear. You may want to look at your clutch hydraulics and make sure it’s fully bled
oh by the way in my experience a clutch going out lends itself to problems getting moving, not putting in gear. You may want to look at your clutch hydraulics and make sure it’s fully bled
There are special cleaners for gearbox, maybe I will use it. Just checked that according service manual gear oil in 4+3 should not be changed
. Maybe thats source of the problem.Thanks !
Thread Starter
Intermediate
Joined: Nov 2022
Posts: 35
Likes: 6
From: Georgia
Possibly, I’m not fancy enough for special cleaners. And I thought it was around 30K or 50k miles for the manual trans gear oil change. As far as I’m aware every fluid in these cars has a service interval.
Intermediate
Joined: Nov 2024
Posts: 27
Likes: 1
From: Warsaw, Poland
According to General Motors, the manual transmission fluid on 1984–88 Corvettes, equipped with the 4-speed manual transmission (with automatic overdrive), does not require changing. However the fluid in the overdrive unit must be changed every 30,000 miles (50,000km). Dexron(r) II, or its latest superseding grade of automatic transmission fluid is the only type of fluid that can be used on these vehicles. The use of any other fluids or additives may damage the transmission.
BTW. I have a question about overdrive. I can switch it, it goes smoothly, get indication light as well. When I accelerate it drop it smoothly as well. Only problem is when I manually switch it off, it jerk. I think it is not normal ?
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Safety Car
Joined: Oct 2007
Posts: 4,426
Likes: 229
From: Pennsylvania
From service manual:
According to General Motors, the manual transmission fluid on 1984–88 Corvettes, equipped with the 4-speed manual transmission (with automatic overdrive), does not require changing. However the fluid in the overdrive unit must be changed every 30,000 miles (50,000km). Dexron(r) II, or its latest superseding grade of automatic transmission fluid is the only type of fluid that can be used on these vehicles. The use of any other fluids or additives may damage the transmission.
BTW. I have a question about overdrive. I can switch it, it goes smoothly, get indication light as well. When I accelerate it drop it smoothly as well. Only problem is when I manually switch it off, it jerk. I think it is not normal ?
According to General Motors, the manual transmission fluid on 1984–88 Corvettes, equipped with the 4-speed manual transmission (with automatic overdrive), does not require changing. However the fluid in the overdrive unit must be changed every 30,000 miles (50,000km). Dexron(r) II, or its latest superseding grade of automatic transmission fluid is the only type of fluid that can be used on these vehicles. The use of any other fluids or additives may damage the transmission.
BTW. I have a question about overdrive. I can switch it, it goes smoothly, get indication light as well. When I accelerate it drop it smoothly as well. Only problem is when I manually switch it off, it jerk. I think it is not normal ?
Melting Slicks
Joined: Nov 2016
Posts: 2,253
Likes: 3,076
From: So Cal
2023 C4 of the Year Finalist - Unmodified
When the cars were new and being driven daily 15-ish K miles a year, the 30,000 mile interval for overdrive service makes sense. Every 2-3 years. But now the overdrives are obsolete. There is limited (none?) parts availability and people that know how how to fix them. If something is beginning to let go internally such as the snap-ring tangs or thrust washer you want to know about it before the unit fails completely. There may be a chance to save some parts (like the case) if you find the problem early. So much shorter mileage intervals now make sense.
For myself, the #1 reason to drop the pan for a service is to look in the pan to see what's in it. You of course don't expect, and don't want to see anything. But if there is foreign material, now you know that something is letting go. I now service the OD in my 85 about every 5 years. Which is about 500-1,000 miles. May seem like overkill, but its 40 years old (38 years since it was repaired with the updates) and I don't want to have to find parts for it.
For myself, the #1 reason to drop the pan for a service is to look in the pan to see what's in it. You of course don't expect, and don't want to see anything. But if there is foreign material, now you know that something is letting go. I now service the OD in my 85 about every 5 years. Which is about 500-1,000 miles. May seem like overkill, but its 40 years old (38 years since it was repaired with the updates) and I don't want to have to find parts for it.