Scott0757

I think in 85, the functionality of the automatic OD functions were changed. How do I wire this so that when the 1st gear switch is open, it will just mean that 2 or 4 are closed so the solenoid will function?

Scott0757

This site matirx on the various 84-89 O/D operational differences:
http://www.5speeds.com/43table.htm

So right now there are only a reverse and first gear switches. I believe the 3rd connection is the O/D solenoid power switch.

Do I need to find an 85 cover plate for the T10 transmission and use the 4th and 2nd connection to work with my 84 ECU, or can I wire things to work with what I have (OD activated unless in 1st or reverse when console switch is on).
Maybe I am stuck leaving the O/D off unless I am cruising on the highway and then turning it on....but at least I will/should have a functional speedometer/odometer,cruise control, etc....

vetteoz

As observed different years had different combinations of switches

Many like to rewire the O/d and make it full manual control which simply means supplying a fused 12V supply through the 1st gear switch so O/d can not be engaged in 1st
Most disengage the O/d for around town anyway , only turning it on when crusing on the highway

Backup switch is only for the backup lights , plays no part in O/d operation

Scott0757

I guess that's where I am heading....If I put the fused 12VDC using the 1st gear switch in the tranny, do I still need to modify/short out the ECU harness wiring and use the OD relay under the hood? The posted KBase article says I need to do that as well....probably to accommodate the O/D turn on/off functionality.

I tried to see if I could get any life out o the O/D solenoid by applying brief taps of 12VDC to to the terminal while grounding the case and heard nothing... as the tranny is on the bench, there should be nothing looking for and other interfaces/ECU criteria, so I expect I would have heard something if it was functional/not seized or in some postion where the OD is locked out. Also in normal operation, does the TB cable that drops out the O/D pull the cable under heavy acceleration or does it release tension? Tired it with and without tension without success on the solenoid. Will have to dissect it and make sure that works when replacing the filter..

In retrospect, I think the O/D solenoid blocks ATF fluid by pushing a ball into one of the hydraulic journals to stop the flow. When no power is applied to the solenoid, fluid flow is restored, so probably would not see here anything without fluid/pressure.

Scott0757

Old Saginaw 4 spd removed. Custom welded support strut bracket for installation on a Vette was on the tail section. Most seals front/rear/shifter shafts were leaking so another reason to change it.
Prepping the Nash 4+3. Lots of sludge in pan...appeared the filter had dropped off but with all the transport I guess that could be expected. Bench test shows functional OD solenoid and speed sensor.

Just need to figure out if I can get it to operate like a 1985 with only the reverse and 1st gear switch connections and none on 2nd or 4th...that might be an ECU change..otherwise it's manual OD for me. Waiting on new clutch and pressure plate arrival as input shaft splines are different from the Saginaw and Nash.

Changing engine real seal and oil pan/valve cover gaskets as there is oil everywhere, even inside the bell housing..hence my occasional rough startout clutch response...

Scott0757

Here you can see the adapter plate on the saginaw tail piece.
The nash is standing up on the bell housing to permit easier cleaning and replacement of filter prior to reinstalling.

jv9999

Looks good on the outside. I'd pull the side cover and the pan on the overdrive. Change the oil in both (if there's any in there). Did you get the driveshaft with the 4+3? You'll need it.

Scott0757

Have drained all the oil from both sections. As can be seen in the pics, the OD unit pan is off, cleaned up and a new filter ready to go in next.
as for the drive shaft, given that the old and Nash will use the same support rail, the length should be right...I thought the output shafts were the same number of splines and diameters. Hope so. Have to go check now so I can sleep tonight!

Scott0757

Drive shaft splines are the same!

vetteoz

The reverse switch is only for the backup lights

Scott0757

That I know. The OD operates differently between 84 (mine) and 85. The 84 has some other ECU connections and I am hoping to be able to get it electronically functional for the kick down feature based upon the throttle valve position... we'll see. Can find any info on people putting an 85 Nash 4+3 into and 84..

vetteoz

I suspect that would require a '86+ ECM
Early versions had the kickdown function via the cable connected to the TB

Scott0757

This is an 85 4+3 with the same TB cable as the 84.

The only difference is on the T10 side cover lacks switches/harness connections on the 3 & 4 shifter shaft. Its like the ECU needs to be told it is not in reverse or first (when it would disengage OD) and if 3rd or 4th (engage OD).

If I am missing the 3rd/4th gear connections to the ECU, will it not allow OD engagement? I may not know until I hook up what I can and try it. Then, if necessary, I may have to do the ECU bypass switch mod. Anyone attempt such a swap or have a T10 side cover with the required 3 threaded switches needed for the 84 Nash 4+3?

bitsa85

I would be interested in buying the trans/adapter if you want to sell them.

Scott0757

I will be looking to sell it with the adapter plate, pressure plate and disc (as a set), but not sure how to go about draining and crating it let alone what it would cost. Any experience doing that? I live in Syracuse, NY and it appears you are in CA. In the spirit of full disclosure, I have not taken it apart, but it appears the prior owner had the side cover off and resealed it with RTV. Most seals do leak, but it did shift smoothly.
We can discuss if you are interested. Still waiting on my new clutch kit to arrive for the Nash install, but expect success so the Saginaw will be surplus...

Scott0757

Clutch kit arrived and installed. O/D filter replaced, pan cleaned. The residual ATF fluid in the pan was pretty sludgy looking but cleaned out what I could without total disassembly. Drained the T10 section fluid looked clean, but boy I hate that hypoid smell! Mounts fine to the same bell housing so things are looking good. Just wish I didn't have to pull the drivers seat and console to pin the shifter mechanism into its neutral position, but I guess it's small, necessary effort given this is a complete transmission type replacement.

Hope to get it mounted up, cooler lines purged and hooked up, fluids filled today.

What do others use to fill these transmissions as it needs to be pumped, not poured in? Trying not to make a real mess...

Scott0757

New clutch and pressure plate on. Bell housing on. NASH 4+3 O/D transmission on. Transmission/ Differential support on. What a crappy design to install and align those 4 bolts!). Driveshaft on...NOT!!!! The driveshaft is about 2.75 inches too long!!!! Noooooo! Off to internet to go shopping for a replacement. Anyone have one to sell? Seem to be a few on ebay but of course the priciest driveshafts listed...most are for automatics...

hemivett

I believe the zf6 driveline is the same. You could also measure yours, and see if you can find a shorter one at a wrecking yard, just use your yoke. Your last option is to have yours shortened about $150, or have a custom one made $500.

There is a lot of how to videos to do it yourself, but thats not a route I would take. h

http://www.ebay.com/sch/i.html?_odkw...shaft&_sacat=0

Scott0757

Happy to report major progress. Found and installed a shorter, aluminum OEM driveshaft for the Nash 4+3. Got transmission cooler lines hooked up, fluids all replaced and was able to take a quick 4 mile test spin as we had 24 hrs when the NY roads were free of snow and crap. (Blizzard underway dropping approximately another foot today though).
Transmission shifted smoothly, but the clutch travel is shorter than expected. It does fully disengage and shifts cleanly, but I may see if bleeding the clutch system helps bring the pedal up a bit. Very happy to report smooth, quiet shifts of the manual tranny , but have not seen life out of the Overdrive yet. This could be due to it not reaching the required operating temp or the harness/ missing 2nd/4th switch situation noted above.

A big benefit to this tranny swap is it had the proper speed sensor. My speedometer, fuel MPG/Range functionality is working for the first time since I got the car last year!!! I forgot to see if the cruise worked in my short 4 mile loop, but it was not in any gear for long enough to test it. I am also not sure of the odometer is recording. Seems to be stuck. May have to look into the stepping motor of that. (Any ideas?)

So now I am back to some interior work. Door panels were a mess and PO had started to paint them (yes started...looked like he stopped after spraying 1/5th of the panel on the driver door.) Carpet was rotting away too, so painted door panel and replaced carpeting. Looks like new...Waiting on delivery of new glass anti-rattle bumpers..

My rebuilt BOSE AM/FM/CD unit having issues playing both front speakers at the same time. When slowly inserting the front speaker connector on the harness to it, the driver door will play and the passenger side will be dead. Once fully seated only the passenger door will play. Not a harness issue as there is some cross talk between them as even pulling one of the passenger door leads out of the harness, the same thing happens. Will use the factory troubleshooting directions, but getting to there door amp connections requires glass lift mechanism removal! Something for later.

Also working to repair a busted off hazard switch...broken at the boss the button screws to.. How do people break these things??? So many fragile plastic parts under the pulled wheel snapped in pieces so I am waiting on replacements, due today.

Still have a small drip off the steering pump to rack fittings to stop. Of course these are nicely located under the oil cooler lines so they need to be removed to reach the rack fittings. So tired of dismantling other things to reach what you want to fix...

All for now. Come on spring!

Scott0757

OK. Have a clutch issue. The clutch sounds like it is not fully disengaging when I have the pedal to the floor. It sounds noisy when the pedal is released and starting to engage, but it quiet when fully depressed or released. I am beginning to think I have a sticky pressure plate finger.. As I am noticing the need to double shift as I drop gears, it leads me to beleive the clutch is not fully releasing.
The pedal throw is very short. It ony feels like I am pushing on the pressure plate when the pedal is very close to the floor and the pedal needs to be fully depressed to disengage at all.
I removed and bled the slave cylinder per factory manual directions and that seems to be fine. When I reinstalled it on the bell housing, I had to compress the plunger on the shifter fork, resulting in fluid overflow from the fluid reservoir.
The fork pivot bolt is properly positioned on the fork. Given that this fork was used in the as recevied Sagniaw transmission and pressure plate and it's throwout bearing seemed to be the same depth as the replacement I got with the clutch set from Corvette Central, I am not sure where to go next. I feel I have a bad pressure plate and hate the thought of having to pull tranny off again on my back in the garage and deal with the support rail, overdive unit hydraulic lines and fluid, but it may be necessary. Any ideas? I'll see if I can get a picture of the existing fork/slave plunger position if I can get the boot back far enough...