4+3 to Automatic Conversion

[l98vette1986]

Im ditching the 4+3, and trowing in a 700R4. I started this project w/ only a rebuildable core of a 700, and I have almost all the parts that I think i need.
Has anyone here ever done this swap, and if so, let me know how it went.

So far i have the tranny, Torque Brace for an Auto (im guessing i need to modify it to fit the Dana44 rear end). I have a drive shaft for an Auto w/ a yoke, im guessing i'll need to combine the 2, using the back half of the 4+3 shaft, and the front half of the auto shaft. I got the shifter, shift cable, brake pedal assembly, passing gear cable and console plate. I know i'll need the tailshaft housing for the auto, and a flywheel.
Im thinking this is all im going to need on this conversion, if anyone has any tips on this, or has doneit before let me know how your swap went.

Thanks

 

[-=Jeff=-]

Im ditching the 4+3, and trowing in a 700R4. I started this project w/ only a rebuildable core of a 700, and I have almost all the parts that I think i need.
Has anyone here ever done this swap, and if so, let me know how it went.

So far i have the tranny, Torque Brace for an Auto (im guessing i need to modify it to fit the Dana44 rear end). I have a drive shaft for an Auto w/ a yoke, im guessing i'll need to combine the 2, using the back half of the 4+3 shaft, and the front half of the auto shaft.

Thanks

You use the torque tube and Drivesaft from the 4+3 just transfer the yoke.

The reason the Driveshafts on the 4+3 and Auto were different was due to the Dana 36 and Dana 44, not the different trans.

I went the opposite way, auto to 6spd. if I would have kept the Dana 36 I would have used the longer Driveshaft and torque tube after the conversion.

 

[l98vette1986]

I have been told the torque brace, and drive shaft are shorter in the 4+3 cars than the autos, and ZF 6 cars.

 

[MBDiagMan]

Why are you bothering to do this? 90% of the C4 Vettes are automatics and there are BEAUCOUP of them out there in nice shape for sale CHEAP.

I realize that this is personal taste, but I wouldn't trade my 4+3 for two equivalent Vettes with automatics.

That's just my opinion, but it doesn't make sense to go to the trouble when there are plenty of cars out there with automatics. So many 4+3's have been changed over to 6 speeds or otherwise altered, that my car is getting more rare all the time.

Good luck,

 

[-=Jeff=-]

I have been told the torque brace, and drive shaft are shorter in the 4+3 cars than the autos, and ZF 6 cars.

I have heard that too, but never confirmed.. Anyway if that is the case you will need a Torque tube and Driveshaft from a 6spd car. then put the Auto yoke on that Driveshaft. the Longer ones from an auto car will be too long

 

[l98vette1986]

Why are you bothering to do this? 90% of the C4 Vettes are automatics and there are BEAUCOUP of them out there in nice shape for sale CHEAP.

I realize that this is personal taste, but I wouldn't trade my 4+3 for two equivalent Vettes with automatics.

That's just my opinion, but it doesn't make sense to go to the trouble when there are plenty of cars out there with automatics. So many 4+3's have been changed over to 6 speeds or otherwise altered, that my car is getting more rare all the time.

Good luck,

Automatics are better for drag racing at the track. The 4+3 w/ working everything is a boat anchor, mine will be for sale w/ all parts included except for a drive shaft when i get the auto in.
Its got a performance clutch, short throw kit, rebuilt master, and slave cylinder, console plate, clutch pedal assembly, and shifter. Im saying good bye to it. So if anyone knows anyone that may be interested, let me know.
BTW what are these transmissions selling for?

 

[MBDiagMan]

So what leads you to say that the 4+3 is a boat anchor. Could you elaborate?

Have a great day,

 

[l98vette1986]

they are crude shifting, rod linkage is crap.
they have plenty of drag to go around, the pump is always turning, putting more drag on the motor, definately not what you would want for drag racing. even w/ a short throw kit the throw is way to far to provide a good shift. the sliders are very weak, power-shifting is almost not an option. I have had to replace a few of them for the 1-2 gear selector. the overdrive units are crap.. just a plain GM Cluster F*ck. I cant think of any reason to keep it. it sucks having to push the overdrive button, and sometimes it doesnt turn off, which is a big pain in the ass if i want to race. The transmission is crap. You can polish it all you want, but its still a turd.
this isnt to offend anyone, but i hate the piece of junk. like i said before, as soon as I can get it out, its sold.

 

[MBDiagMan]

Thanks for the elaboration. You make a good case for it not suiting YOUR purposes.

Given the time period in which it was designed and put in these cars, for NORMAL, albeit a bit spirited driving, it is actually a reasonably good piece. I do believe that they would've been better off building a good five speed or six speed transmission. There was nothing around they could buy for a reasonable price to handle the torque.

They did screw up IMHO by combining off the shelf parts to make it rather than just building a five or six from scratch. The problem is that GM has accountants making engineering decisions. The front portion of the trans is a standard four speed box of the time with the rear being a standard planetary and clutch pack of the time. I'm quite sure that they saved a lot of money doing this in lieu of building the correct transmission for the application.

Another thing I find a bit comical about it is the Doug Nash name used. I expect that the only involvement that Doug Nash had was receiving the payment for using his name.

It all comes down to your particular use. Just because it does not suit YOUR application doesn't mean that it's no good for ANYTHING. If a dump truck driver had to drive a Ferrari he could easily call it a boat anchor because he can't haul much gravel. It doesn't mean that the Ferrari is no good, it just means it is not correct for his needs.

Good luck with your automatic.

Have a great day,

 

[Ken]

The June issue of Corvette Fever has a letter in the Tech Line column that answers your question. As a matter of fact Chris, I had to look at the signature to be sure it wasn't you, but you're not "Tony." :L

Anyhow, the guys got an '85 that he wants to ditch the 4+3 in favor of an automatic, specifically the 700-R4. Our friend Dave Emanuel has this response:

You want to take a perfectly good Corvette and ruin it by swapping a manual transmission for an automatic? In the name of political correctness, I won't make any disparaging remarks about your proposed swap, but you may be in for more work than you anticipate.

Removing the 4+3, bellhousing and clutch assembly, and installing a 700-R4 in their place isn't terribly involved. The necessary changes to make the conversion functional is a different matter. You'll need to plumb up a transmission cooler, install a driveshaft and torque arm from a C4 originally equipped with an automatic transmission, and connect a throttle-valve cable that runs from the trans to the throttle linkage. The torque arm swap is related more to rearends than transmissions; C4s originally equipped with automatics have Dana 36 rear axles, and those that rolled out of the factory with a manual trans were fitted with Dana 44 rears. It will also be necessary to adapt a shifter to your car, drill a hole for the cable that runs from the shifter to the trans, and install a console plate for an automatic transmission.

If you want the torque converter clutch (TCC) to operate like an original installation, you'll need to rework the harness to incorporate the connector for TCC controls. Then you'll need to install the appropriate PROM in the ECM. As an alternative, you can install a stand-alone TCC control from companies such as TCI Automotive.

Hope that helps you in your decision-making process.

 

[MBDiagMan]

There are so many nice cars out there, cheap, with automatics it seems like it would be better to find a nice one. If you have lots of extras in your present car, swap them to the new (to you) car and then sell the manual trans car. I think it would be less trouble and give you a chance to make it exactly what you want.

My $0.02,