1988 c4, 4+3 transmission swap?

[Oldskool153]

I have an 88 c4 with the 4+3, its my first vette and I like her alot, she runs good and shifts great (except for the fact that my OD switch doesnt disengage OD, but better to be stuck in it than stuck out of it) anyway it shifts great but today I noticed that when i gun it in first and try to shift quickly into 2cd it shifts hard (as in not wanting to move out of 1st and into 2cd) It only does it when I gun it in 1st, if i get up to speed at a normakl rate it shifts fine and smooth. Any idea what can cause this, culd it be just in need ot a service? And if my trans does go bad How hard is it to swap in a 5 speed summit trans into my car? Thanks in adavance

 

[vetteoz]

my OD switch doesnt disengage OD,

Check that the switch mounted on the gear lever is operating properly

when i gun it in first and try to shift quickly into 2nd it is hard to shift

shift linkages / bushes worn.
Bolts holding C beam to trans loose allowing trans to move and bind up shifter under hard accel
Shifter is mounted to body so any movement between body and trans could cause alingment problems.

 

[Oldskool153]

Thanks Im going to buy a corvette manual this week, either a haynes or a fsm, should both cover the information on how to do this? thanks

 

[vetteoz]

FSM only , try eBay.
Haynes tells you nothing but generic stuff.

 

[johnny80]

4+3 Swap

This site has been a godsend for me and has saved me thousands of dollars and hours. Great bunch of owners and mechanics who know C-4's up and down and they will steer you in the right direction.

Bottom line: take some time, ask questions and do your homework with this website. I first had the mentality that shops would do work like Overhaulin and Chop / Cut / Rebuild on TV and the work ethic would be to work day and nite on my car, not so.....4+3 transmissons take time to find and be prepared for that. It was worth the wait because she runs great now.

I too have an 88 with the 4+3 and for years thought about doing the swap for a Tremec 5 speed. Unfortunately, the cost would be more than the budget I had at the time. I was fortunate enought to take it to a reputable transmission shop (After endlessly searching around, meeting face to face and asking basic questions and found out via the Better Business Bureau research as well as ). Most transmissions places haven't even heard of the 4+3 and don't know the quirks of the operation. I sat down with the owner and he found used 4+3, installed it, replaced the clutch and slave cylinder all for around 3800.00. I couldn't be more pleased with the results. The shifting is smooth, no more road noise while OD off and the switch is relayed so I can turn it off and on without it automatically kicking on. I prefer that while driving on residential streets and use the OD for speeds above 45 or on the highway.

Best of luck!

 

[vetteoz]

and the switch is relayed so I can turn it off and on without it automatically kicking on.

As it comes from the factory;
if after starting ,you push the O/d button before driving off, it removes ECM control of the O/d .
It can then be engaged/disengaged manually whenever you want. Kickdown out of O/d is still operational.
The switch is a trigger signal to the ECM ; not to the O/d relay.

 

[johnny80]

Your exactly right Oz...that is how mine works.

 

[fastred87vette]

I have an 88 c4 with the 4+3, its my first vette and I like her alot, she runs good and shifts great (except for the fact that my OD switch doesnt disengage OD, but better to be stuck in it than stuck out of it) anyway it shifts great but today I noticed that when i gun it in first and try to shift quickly into 2cd it shifts hard (as in not wanting to move out of 1st and into 2cd) It only does it when I gun it in 1st, if i get up to speed at a normakl rate it shifts fine and smooth. Any idea what can cause this, culd it be just in need ot a service? And if my trans does go bad How hard is it to swap in a 5 speed summit trans into my car? Thanks in adavance

keep that 4+3 its a very tricky one but my friend have a 4+3 (86) and he show me how it works and its great... get off in first, then get into 2nd O/V OFF at any rpm then stay O/D OFF TO +/- 4300 RPM AND JUST PRESS ON THE O/D ON THE SHIFTER AT WOT... THEN GO TO THE 3RD GEAR WITH O/D OFF AND KEEPING IT WOT PRESS THE SWITCH TO OD/ON AND SO :W CRAZY IS THE RESULT .... NOBODY :bash HOW TO HANDLE A 4+3 AND EVEN FEWER HOW TO GET THEM FIXED SO ENJOY IT THE WAY IT WAS BUILTED...

 

[vetteoz]

JUST PRESS ON THE O/D ON THE SHIFTER AT WOT... ...

:ugh
O/d will last much longer if you use the clutch when on/off the O/d.
Takes the load off unit as it shifts.
You can gear split as noted ; 2nd -2nd O/d -3rd -3rd O/d but the O/d ratios are very close to the next gear up.Save the O/d for cruising;

However it is very handy in slower traffic say 2nd O/d (which is very close ratio to 3rd )
When you need to pull out and pass hitting the throttle automatically drops it straight back into 2nd direct=instant accel.

 

[fastred87vette]

SORRY ABOUT THE ***NOBODY*** I WAS SUPPOSE TO ADD IN MY CORVETTE CLUB AND YOU MIGHT BE RIGHT VETTEOZ THAT IT MUST BE HARD ON THE O/D UNIT THE WAY HE DID THE SHIFTING AT WOT !!!

 

[skybolt31]

Another alternative is to swap the T5 transmission in:

1984-1988 Corvette C4 T5 Swap

This is a good low dollar swap that should work fine for cars that are basically stock.

 

[vdogamr]

As it comes from the factory;
if after starting ,you push the O/d button before driving off, it removes ECM control of the O/d .
It can then be engaged/disengaged manually whenever you want. Kickdown out of O/d is still operational.
The switch is a trigger signal to the ECM ; not to the O/d relay.

I have been asking about a similar condition in the The "Doug Nash 4+3"... thread. My OD is always manual except that the default is on. It is on in every gear, at every rpm, no matter what I do unless I hit the button and turn it off. I have recently just been turning it off until I need "5th" gear. Any suggestions? Or should I just be happy that I have full user-control of my overdrive?

 

[vetteoz]

Any suggestions? Or should I just be happy that I have full user-control of my overdrive?

Given the control problems most have I would be happy with your situation.
However you could try testing to see if it does what it supposed to under the conditions listed in the link below.(87-88)
Doug Nash Overdrive Comparisons

As I stated in your other post the physical side appears to working fine , just no auto ECM control.The circuit in the ECM is obviously working because you can manually command it from the button.
The only thing I can think off is if someone has reprogramed the O/d settings on the chip.

 

[topless82vette]

Another alternative is to swap the T5 transmission in:

1984-1988 Corvette C4 T5 Swap

This is a good low dollar swap that should work fine for cars that are basically stock.

T-5 won't live behind a 350 even a stock one. I have a ex L-98 with TBI and it can tear a T-5 up with ease. The whole weak point is hard second gear shifts that trash them as well as hard first gear take-offs. There were actually 2 5th gears used in the f-body T-5 though. I think the TPI cars got .68 5th while the TBI 305 .63

 

[laurence spillman]

4+3 trans swap to 5 speed

This site has been a godsend for me and has saved me thousands of dollars and hours. Great bunch of owners and mechanics who know C-4's up and down and they will steer you in the right direction.

Bottom line: take some time, ask questions and do your homework with this website. I first had the mentality that shops would do work like Overhaulin and Chop / Cut / Rebuild on TV and the work ethic would be to work day and nite on my car, not so.....4+3 transmissons take time to find and be prepared for that. It was worth the wait because she runs great now.

I too have an 88 with the 4+3 and for years thought about doing the swap for a Tremec 5 speed. Unfortunately, the cost would be more than the budget I had at the time. I was fortunate enought to take it to a reputable transmission shop (After endlessly searching around, meeting face to face and asking basic questions and found out via the Better Business Bureau research as well as ). Most transmissions places haven't even heard of the 4+3 and don't know the quirks of the operation. I sat down with the owner and he found used 4+3, installed it, replaced the clutch and slave cylinder all for around 3800.00. I couldn't be more pleased with the results. The shifting is smooth, no more road noise while OD off and the switch is relayed so I can turn it off and on without it automatically kicking on. I prefer that while driving on residential streets and use the OD for speeds above 45 or on the highway.

Best of luck!

you could have swaped to a richmond 5 speed for approx 3000$ your trans shop went all the way on price a rebuilt OD unit is approx 1500$

 

[vetteoz]

a rebuilt OD unit is approx 1500$

01-24-09
Nearly two years too late with your response :eyerole

 

[vetteboy86]

you could have swaped to a richmond 5 speed for approx 3000$ your trans shop went all the way on price a rebuilt OD unit is approx 1500$

Hi Laurence,
Welcome to the CAC.