4+3 Trans Question

[Talon3156]

Kinda new around here.. I have a C4 with a 4+3 that seems to have a mind of it's own.. It works when It wants to.. Electrical? or something else

 

[CharlesBrown]

Kinda new around here.. I have a C4 with a 4+3 that seems to have a mind of it's own.. It works when It wants to.. Electrical? or something else

If you have not changed the fluid in the "automatic" section of this transmission in the last year, do that. If the gear changes are erratic there are two relays that should be somewhere around the battery (on the firewall) you should change. They are cheap.
Having said all this, the trans. will normally change into overdrive automatically (unless you tell it not to with a switch or push button) in 2,3,and 4. That is unless you have a heavy foot. Somewhere around 3000 rpm it will automatically down shift. All this is normal

 

[muddywaters]

I think, at least on the 88's, Push the O/D button after you start your Vette and it cancels the O/D. I found that out on this site, owners manual was vague. I already jumpered a switch on the tranny and I only get the O/D@ 120 degrees eng. temp in 4th gear, before or after that occurs if I hit the O/D button my O/D is gone until I ask for it, I like driving the car much better. You'll know if the fluid hasn't been changed in the O/D, the magnet will be covered.

 

[Talon3156]

Wow thanks for the response.. and Well here goes my inexperience and lack of knowledge.. What kind of fluid do I use and can you give me some idea as to the relays I'm looking for...

 

[muddywaters]

Can't help you on the relay, haven't had that problem yet, check your owners manual, my 88 took Dextron ATF in the O/D unit, you will also need a filter, search this site.

 

[vetteoz]

What kind of fluid do I use and can you give me some idea as to the relays I'm looking for...

Dextron III reg , not synthetic ATF
The O/d relay is on the firewall next to the fuel pump relay.
Brown
Green
Pink /blk
Tan / blk wires

 

[dknight]

Hi Muddywaters,

I have a 87 convertible with the 4+3. My switch has never worked and I would like to repair it myself...got any tips you would like to share? Thank you in advance.

David

 

[vetteoz]

My switch has never worked and I would like to repair it

Go to Radio Shack and buy one of these.
Mini SPDT 3-Amp Momentary Pushbutton Switch -
RadioShack.com
Must be momentary switch for '87 , not OFF/ON switch
Replace the switch located at the base of the shifter; requires soldering

 

[vetteoz]

you will also need a filter.

Do not buy a expensive filter from a Corvette shop
The OD filter is the same as the one used in Ford FMX trans.
CarQuest 85926
AC Delco TF-184
FRAM FT1024
NAPA ATP 14717
Ford D0AZ-7A098-A

seems to have a mind of it's own.. It works when It wants to..

Need more details.As noted above the O/d will automatically engage when certain conditions are meet.Yours may be operating fine but the filter change and top up is worth the effort

 

[Talon3156]

Many thanks

To all you guys... This site rocks..

 

[Talon3156]

Is the shifter switch the same for a 86?

 

[vetteoz]

Is the shifter switch the same for a 86?

Does the '86 have O/d button on console or shifter ?
'86 requires same type of operation (momentary switch) but switch style will be different if mounted in console.
One linked above is for shifter where it is operated by a rod from the button ( need to remove plastic button that comes with new switch )
'84 and '85 need a Off / On switch

 

[Talon3156]

My 86 has the button on the shifter.. Thought I would switch out the switch because I don't know how to check to see if it works..

 

[WhalePirot]

I don't know how to check to see if it works..

One of the first steps is to see if the dash light comes on or not when the O/D is selected. That helps isolate if the problem is electrical or other. With a 4+3 Corvette of that age, the function of the O/D may have been altered from stock by rewiring.

I suggest three things: 1) get the FSM from Helm and learn how it is laid out, especially the troubleshooting flow diagrams, 2) use the search in this forumk, as there are many posts on this topic which may help you learn and fix things much faster, 3) learn how to maintain the O/D, which is a tough and great, if maligned unit. Proper maintenance is essential for it to last and operate properly.

The ECM must be in closed-loop mode to allow O/D operation. I once fixed a cycling unit by installing new plug wires.