4 + 3 transmission

[jim510]

Hi all...I just bought my first Corvette....a 1987 coupe with a 4 + 3 trans....the car was stored for a few years and I guess the guy just wanted to get rid of it....anyhow, I seem to be having a few problems with od....sometimes the light would come on for a few minutes and then go off....now it seems it doesn`t go into od....I put fluid in the box and I also replaced the relay...no luck...other than that, the car runs pretty good....I didn`t find any loose wires, and I`m not sure where to go next....any help with this would be greatly appreciated....thanks in advance......Jim

 

[muddywaters]

Service the O.D unit, filter and fuild, you hear horror stories about the 4+3, but mine has been no trouble, yet. When I bought the 88, I serviced the OD unit , the magnet was covered pretty good with particals, which indicated to me that it wasn't serviced much. I got the filter/gasket from Ecklers and had a problem leak from the pan, I dropped the pan the second time and used RTV silicone instead of the supplied gasket, which is what the repair manual recommends. Since then the OD unit is working flawlessly. We can only hope that my luck continues.....................I also put Redline trans. lube in the 4spd and shifting feels better..................

 

[jim510]

Thanks....will order the filter and replace fluid...

 

[muddywaters]

There's other outlets for those OD filters, search this site......................

 

[Toms007]

Welcome to CAC Jim. You'll find really nice people here more than willing to help with any thing they can.

Mods....I think this particular thread would be better in C4 Tech.

 

[jim510]

thank you all....nice to meet you all

 

[rrubel]

Welcome to the CAC... This site - http://www.corvetteobsession.com/ - has a ton of great info on the 4+3 (its originator was a fixture on CAC before his death). You may want to check the switches on the side of the transmission that tell it what gear it's in, and also have you tried manually switching in and out of OD?
[RICHR]

 

[jim510]

What I found is that I have a small leak around the gasket in the od pan....i topped it off again, and the light came on again....I tried to buy a filter in every auto parts store around here and nobody had it....I had to order it online and it will take a few days to get here...at least I know what I`m dealing with now...thank you all for your input...Jim

 

[rrubel]

IIRC the filter is also the same as the auto transmission filter for the Ford Ranchero, which is carried more places (believe it or not).
[RICHR]

 

[JimBobC4]

IIRC the filter is also the same as the auto transmission filter for the Ford Ranchero, which is carried more places (believe it or not).
[RICHR]

The Ranchero came with 4 different auto transmissions.

1. the C-4 for Small block 289 302
2. The C-6 for Big Block and some 351 C applications and 351 w ( I think )
3. The FMX tranny in some early 1970's appications with a 351 M
4. The Cruise O matic out of early Fairlanes and Mustangs ( Early C4 )

What year of Ranchero is interchangeable ?

It sound reasonable as I have read that the overdrive unit was
designed by Doug Nash for Ford based RV chassis in the mid to late 1970's. I would be curious, if it was the C-6 version as that is what was in the Rv's at the time.

 

[tcolyer]

The Ranchero came with 4 different auto transmissions.

1. the C-4 for Small block 289 302
2. The C-6 for Big Block and some 351 C applications and 351 w ( I think )
3. The FMX tranny in some early 1970's appications with a 351 M
4. The Cruise O matic out of early Fairlanes and Mustangs ( Early C4 )

What year of Ranchero is interchangeable ?

It sound reasonable as I have read that the overdrive unit was
designed by Doug Nash for Ford based RV chassis in the mid to late 1970's. I would be curious, if it was the C-6 version as that is what was in the Rv's at the time.

#3 The FMX transmission - Auto Zone has the filter for less than 10 dollars and is part # TF-124

 

[John '85]

Service the O.D unit, filter and fuild, you hear horror stories about the 4+3, but mine has been no trouble, yet. When I bought the 88, I serviced the OD unit , the magnet was covered pretty good with particals, which indicated to me that it wasn't serviced much. I got the filter/gasket from Ecklers and had a problem leak from the pan, I dropped the pan the second time and used RTV silicone instead of the supplied gasket, which is what the repair manual recommends. Since then the OD unit is working flawlessly. We can only hope that my luck continues.....................I also put Redline trans. lube in the 4spd and shifting feels better..................

Hey Muddywaters, what grade of Redline did you use? MTL or MT90?

John

 

[johnny80]

Welcome to the CAC! This site has been a godsend for me since I bought my vette in 02. My 88 has the 4+3. I have gotten alot of great guidance from the folks here. I have probably saved myself thousands of dollars in repair expenses just by asking questions. I was never much of a wrench turner but over the years, my confidence has grown and I have been able to replace many parts such as alternator, battery, exhaust, cooling fans, TPS and much more by maximizing the expertise of the individuals on this site. Make sure you get your hands on a GM repair manual, it's worth the investment. Congratulations again on your vette.

 

[muddywaters]

John85, I used MT90, the tranny (Not the OD unit, it uses ATF) shifts much smoother................

 

[mike53]

4+3 O/D service

Hi. I just joined this forum to see if I could get some info on my car. I have a 1985 with t he splendid 4+3 transmission. I was reading that these need to be serviced. I have recently started to get a symptom where the O/D cuts out at temps over 192 degrees. Even though this car has only 35.8k miles, I'm sure it has never had the tranny serviced. I did change the tranny fluid last summer. Does anyone have pix or other info on how to service this thing? There aren't many dealers in my area that I trust working on this car, so I would probably be doing it. I look forward to learning more. Thanks.

Mike

 

[vetteoz]

I was reading that these need to be serviced.
Mike

Regular sevice = change fluid and filter ; not disassemble unit. Most owners treated them as an other automatic and did not change fluid often enough.