85 'Hanger Queen'

Hi guys. First thread, long time lurker. Sorry in advance if this has been addressed already.


My 85' is equipped with the DN 4+3. Production number is 16,103, which means it's right smack in the middle of the production run. It could be a late model or an early model. I'm aware of the differences between early and late, mainly the location of the overdrive switch. Early models have it on the console, late models have it on the shift ****.


My vet has both..... (let that sink in)


My guess is that someone did a tranny swap. How else do you explain a late model shifter **** (including the threaded T-rod and the switch at the base of the rod) AND the console switch?


It'd be pretty easy to rule out which is the original equipment, only that my OD is inop. I'm about to start troubleshooting (Yes, I've read the countless threads. Good stuff.)


The real question; what complications could arise from trying to install a late model 4+3 into an early model C4? Are they wired the same? TV cable? etc. And how can I verify that this is in fact a newer 4+3?


Thanks. You guys rock.


-Al

VikingTrad3r

subbed, I just acquired my 4+3 myself sorry I don't have much in the way of feedback for you.

85 'Hanger Queen'

No worries, thanks anyhow. What does "subbed" mean?

jv9999

Does the trans have a throttle cable? If not, then it's a later model. If you just want to see if it works apply 12V to the white connector behind the shift levers and take it for a ride. If it works, it will be in OD (all 4 gears) as soon as you hit 3 MPH +/-. You don't want to leave it that way, but it's good for a quick test. After than it's about the shifter switch and the relay.

85 'Hanger Queen'

Ok will do.


The good news is, I get to choose if I want the switch to be on the **** or on the console lol.


Thanks!

JWMorrisey

Greets
I picked up a '86 w/ the DN 4+3 and the switch on the shift **** is way cool IMHO.

My overdrive unit needs rebuilding as the OD clutch is burned out. I'm driving it as a traditional 4spd w/ the relay disconnected until I can get the unit rebuilt.

Right now, I'm shopping for a used unit in rebuildable condition so I can get it rebuilt and then swap it in or rebuild it myself and then swap it in. I'm a former ASE master tech and I found the complete tool set still in its carrying case back in the winter.

I have read a post somewhere in another thread where there is a reprogrammed chip out there that takes away the automatic upshifts into overdrive and turns the request button into a shift button.


BTW Have you purchased a FSM for the car yet? The digital version on CD is way cheaper and takes up less room to store.




Keep us posted on your progress.
Jonathan.....

BV85

JWMorrisey If you do rebuild the overdrive unit PLS let me know. I just turn wrench's for a hobby but know that that unit is way above my level. TIA

Silver85

It means he has subscribed to the thread by replying so he can follow the progress.

85 'Hanger Queen'

Agreed, I'm partial to the pushbutton on the ****. I do believe I'll wire it up and use it instead of the toggle.


Good luck on the rebuild. I purchased the FSM on CD rom for about 35. Well worth it. Gives a lot of detail on troubleshooting the OD. I'm on the lookout for the assembly manual next. I'd like more detail on the door panels and interior construction. The exploded views are good, but more detail is always better.


The chip upgrade sounds pretty cool. That's exactly the way I'd want the OD to operate. I want to dictate when it kicks in. Honestly, I'd only use it in 4th gear. I couldn't care less if it works for 2 and 3. Those gears are just about fun anyway.


I'll definitely keep you guys posted. Currently working on a better floor jack and some stands so I don't have to live in the hobby shop and pay for a lift. Also considering portable lifts.....

85 'Hanger Queen'

Hello again! Finally started digging back in.

Figured out that I have an 86 transmission. Someone must have swapped as I originally expected.

I only have the 1st gear switch, no TV cable (that i can see)

I want to make a jumper from the battery just to see if the OD solenoid engages. Any tips on that? The connector seems to have one prong. Would I just do a jumper wire staight from the positive terminal on my battery and touch it to the prong on the OD switch? Never done it before. Any tips would be greatly appreciated.

Thanks mate!

jv9999

Yes, but an inline fuse would be a good idea (10 amp or so). Keep in mind that nothing will happen until the car starts moving.

85 'Hanger Queen'

Ok, will do. I read another thread where they suggested wiring in a switch as well. I'll update you guys on how it turns out.


Thanks again.

85 'Hanger Queen'

So I rigged up a jumper wire with an in-line fuse and a toggle switch, from the battery directly to the OD unit. Voila! OD engaged and worked like a champ every time. It feels good knowing that my unit isn't shot. I wired it back up and did a fluid/ filter swap and cleaned the console switch contacts. Current status: OD operates intermittently, ie; comes on when it wants to.

I do believe that this car has been modded to bypass the ECM due to the way the OD operates when it's actually working- it's either on or off in 2nd, 3rd, and 4th. Plus, it doesn't automatically kick out of OD when you get on the throttle. Strangely, It seems to only work when the car is warmed up, though. I've never seen it come on with the temp below 180.

My question for you 4+3 gurus is this:

If the ECM has been bypassed, and fluid level is good, what else would cause intermittent operation? Based on what I've read, temperature related issues (temp. sensor, thermostat, etc.) shouldn't be a factor here since the ECM is out of the equation. As I understand it, once the switch is thrown, the OD should kick on regardless.

Thanks again bros.

jv9999

The not working below 180F is by design, so the ECM is in control. Also the engagement in 2-3-4 is by design. Does the OD light come on but it doesn't engage? It could be a bad OD relay. If the light doesn't come on either, you might connect the car to a scanner and make sure all the sensors are in a reasonable range when it decides to not work.

85 'Hanger Queen'

OD light has never come on when the OD is actually engaged, or otherwise. I tried swapping the bulb, but it didn't fix the problem.

If the ECM was still in control, wouldn't the unit work as designed, ie; kicking out of OD ("down shifting") when there's increased throttle demand? At least, that's what the legendary C4 4+3 chart seems to convey. I'm talking about the chart with green letters/ black background that shows OD function for different model year C4s.

.

VikingTrad3r

something I just thought of, the early 85, actually I think it was most of the 85 model year, came with the centre consul mounted overdrive button. But in the late 85 model year they did have them mounted on the top of the shifter. I wonder if you have Miss matched componentry and if that would affect the wiring? Just throwing ideas out there I’ve never troubleshoot it the overdrive electronics before.

85 'Hanger Queen'

Yes you’re correct. My VIN puts my vette as an early 85’, and I have a console OD switch. I figure someone swapped the trans with a newer one that has the switch in the stick, but didn’t wire it up.

GregMartin

Sounds like the shifter has been changed as well because you have one with the button on the top. (There is actually no need to swap the shifter so that’s interesting). The cars that don’t have the TV cable for kick down use the TCC function on the ECM. I guess your ECM is not programmed this way because the car was originally fitted with a TV cable style transmission.

jv9999

The only thing the TV cable does is adjust line pressure in the OD unit (how firmly it shifts). The ECM knows nothing about it. It simply requests OD, which triggers the relay, which sends +12V to the activation solenoid. There is also a pressure switch inside the OD that will keep it from activating if the line pressure it too low. Electrically it's pretty simple.

GregMartin

The throttle valve cable controls the line pressure, downshifting, and the shifting feel in the transmission.