700-R4 Swap

[Tim81]

Hello fellow 81ers,

I have a chance to pick-up a 700R4 trans. cheap. Does anyone know what is involved in swaping out the TH350C. I know that the 82's had this trans. so I'm hoping for a easy swap. If you can give me any info on this that would be great.....Tim

 

[KANE]

Hello fellow 81ers,

I have a chance to pick-up a 700R4 trans. cheap. Does anyone know what is involved in swaping out the TH350C. I know that the 82's had this trans. so I'm hoping for a easy swap. If you can give me any info on this that would be great.....Tim

Tim-

You'll need to-

• either modify your corss member, purchase one for an 82, or buy a new cross member that fits the C3/700R4 combo.
• shorten your drive shaft
• purchase a 700R4 throttle valve cable
• connect the TV cable to the carb through a bracket that fits the 700R4 TV cable
• install either a brake switch or valet switch for the lock-up

Here's a site that has a lot of the details.

Hope that helps!

 

[shark454]

They put that transmission in more cars than the Corvette. They have different levels of "strength". You might make sure the trans has the better upgrades, or maybe upgrade before you install it. It should be a great transmission for your C3 when you're done. Good luck!

 

[Tim81]

Thanks Kane, thats very helpful......Tim

Tim-

You'll need to-

• either modify your corss member, purchase one for an 82, or buy a new cross member that fits the C3/700R4 combo.
• shorten your drive shaft
• purchase a 700R4 throttle valve cable
• connect the TV cable to the carb through a bracket that fits the 700R4 TV cable
• install either a brake switch or valet switch for the lock-up

Here's a site that has a lot of the details.

Hope that helps!

 

[Tim81]

They put that transmission in more cars than the Corvette. They have different levels of "strength". You might make sure the trans has the better upgrades, or maybe upgrade before you install it. It should be a great transmission for your C3 when you're done. Good luck!

Are there any tell tale signs on the tranny that would indicate if its a good one or not? Thanks Tim

 

[KANE]

Tim- when I did my 700R4 swap, I had a TH350 in my 78... not the TH350C which was factory for the 81s.

The TH350C already has the lock up function for the torque converter. So, you may be able to reuse some of the pieces and parts associated with the lock up function on the car- perhaps the brake switch itself. However, since I've never done the swap with a TH350C equipped car, I'm not sure how much is there already. If you have an assembly manual with the wiring schematic for the 81, you could look at it side-by-side with what is needed for the 700R4's lock up and then figure out what you don't have and will need to install.

Also, as shark454 said, some 700R4s have better components. Example- IROC Camaros had the Vette servos while V6 trannys didn't have as many clutch packs. Either way- I'd get the 700R4 rebuilt and fortified with stronger parts. Even if it a bit overkill- at least that will be one less thing to worry about. Especially if the tranny's OE application is unknown.

 

[Tim81]

Tim- when I did my 700R4 swap, I had a TH350 in my 78... not the TH350C which was factory for the 81s.

The TH350C already has the lock up function for the torque converter. So, you may be able to reuse some of the pieces and parts associated with the lock up function on the car- perhaps the brake switch itself. However, since I've never done the swap with a TH350C equipped car, I'm not sure how much is there already. If you have an assembly manual with the wiring schematic for the 81, you could look at it side-by-side with what is needed for the 700R4's lock up and then figure out what you don't have and will need to install.

Also, as shark454 said, some 700R4s have better components. Example- IROC Camaros had the Vette servos while V6 trannys didn't have as many clutch packs. Either way- I'd get the 700R4 rebuilt and fortified with stronger parts. Even if it a bit overkill- at least that will be one less thing to worry about. Especially if the tranny's OE application is unknown.

Kane, I agree with doing a rebuild, the tranny was used in a circle track car so who knows how long its been since its seen anything past 2nd gear. If I decide to take on this project I would have to go through it with a fine tooth comb. Thanks for your help..Tim

 

[Peer81]

Maybe a little late but first I would go with a 700R4 after '87. Has the MD8 sign on the right or left front. After '87 are stronger transmissions also with an other oil pump design. Also like Shark says, go with a transmission that was used in something like a Corvette, then you know the internals are up to the task. On the other hand if you going to rebuild it (as you never know what you have with a second hand 700R4, it doesn't really matter I think.

As far as I know, you can put the lockup connector from your '81 directly into your 700R4. I disconneted mine because I want to get the carb running right first. In the beginning she wanted to stall at low speeds and if after a corner or IN a corner the lockup is turned on you're not happy!

Greetings Peter

 

[spikebot 81]

Hello fellow 81ers,

I have a chance to pick-up a 700R4 trans. cheap. Does anyone know what is involved in swaping out the TH350C. I know that the 82's had this trans. so I'm hoping for a easy swap. If you can give me any info on this that would be great.....Tim

Are you still useing the computer control system?

 

[TimAT]

As noted an post '87 trans is a good start. Add a few things and it's even better.

Front pump- swap the pump rotor and vanes for a 10 or 13 vane pump with hardened rings.
Reaction Sun Shell- there's one called the "Brute" not quite a billet piece, but close.
Rear Planetary set- make sure the one you have is the late design- tougher gears, better oil control. Identified by a tin oil slinger on the back. The outer ring where the parking pawl has all the edges rounded a little bit and one or more of the lugs has a machined groove top to bottom.
Use the Corvette Servo and TV boost valves
Those parts, along with building it with the faced clutch plates and steels from a 4L80 and a Trans-Go kit. Keep all the clutch pack clearances at the OEM spec minumum, if you can add another face/steel plate pair and keep that spec, do it, and a 700 will be pretty tough.

 

[Tim81]

Are you still useing the computer control system?

Yes I'm still using the CCC so the lock-up should be easy.

 

[Tim81]

As noted an post '87 trans is a good start. Add a few things and it's even better.

Front pump- swap the pump rotor and vanes for a 10 or 13 vane pump with hardened rings.
Reaction Sun Shell- there's one called the "Brute" not quite a billet piece, but close.
Rear Planetary set- make sure the one you have is the late design- tougher gears, better oil control. Identified by a tin oil slinger on the back. The outer ring where the parking pawl has all the edges rounded a little bit and one or more of the lugs has a machined groove top to bottom.
Use the Corvette Servo and TV boost valves
Those parts, along with building it with the faced clutch plates and steels from a 4L80 and a Trans-Go kit. Keep all the clutch pack clearances at the OEM spec minumum, if you can add another face/steel plate pair and keep that spec, do it, and a 700 will be pretty tough.

The tranny that I'm looking at appears from the Vin to be out of a 87, so it might be a good candidate.

 

[Peer81]

Yes I'm still using the CCC so the lock-up should be easy.

Well, I see I said this but it's not that easy. It all depence what switches your 700R4 already has on the valvebody. To say it very easy. With the '81 the ECM is controlling nearly nothing for the lockup and the most is controlled in the 350C. With a 700R4 most is controlled by the ECM and nothing in the transmission. If you check my lockup problem topic in technical you'll see the problem.
Hope it helps.

Greetings Peter

 

[Tim81]

Well, I see I said this but it's not that easy. It all depence what switches your 700R4 already has on the valvebody. To say it very easy. With the '81 the ECM is controlling nearly nothing for the lockup and the most is controlled in the 350C. With a 700R4 most is controlled by the ECM and nothing in the transmission. If you check my lockup problem topic in technical you'll see the problem.
Hope it helps.

Greetings Peter

Thanks Peter, I'm still not sure if I want to use this trans, I know its a 87 and came out of a Caprice, so I'm pretty sure it was built for a V8. Most people are telling me to use a trans built after 87 so that worries me some. Swap will not happen until next year, I just finished the engine and will be putting back into the car this weekend, just in time for summer. The tranny swap will be a winter project.....Tim

 

[TimAT]

SInce that swap won't happen until next summer, I'd go thru it in my spare time- it's not that tough, and you can do a bunch of upgrade stuff as you rebuild it. Even if it comes from a car with a V6- the difference in the hard parts is minimal- a couple of spacers that can easily be removed and more clutches added. All the valve body stuff gets corrected when you install a shift kit.
Automatics are not really difficult, but they DO require you pay attention to detail. One of the really nice things about a 700 is you can air check all the clutch packs for leaks before you assemble the trans. And 5 PSI is plenty.

 

[GerryLP]

The number of mods is what kept me away from a 700-r4.

I opted instead for a 200-4r, and the swap is perhaps 1/3 easier and cheaper. The stock driveshaft fits, the stock transmission cable bracket works fine for the TV cable, the cross member was readily available (I used the Bowtie Transmissions because it has the bracket for the E-brake cable pulley), the transmission's dimensions are very close to the TH350c, it fits the lockup harness clip as in the stock tranny, and the stock exhaust fits as well (but the hanger that bolts at the stock tranny's rubber mount no longer fits without extensive modification or complete redesign and manufacturing of a new one).

I cheated, however. I bought a Raptor tranny from PATC, and it came with the dip stick, tv cable, and other parts. I have a series of posting I did last May on the subject.

GerryLP:cool

 

[Tim81]

Thanks Gerry,

I am thinking about using the 200r4 instead of the 700, just because it looks like a better fit. The only reason I'm considering the 700 is that one became available to me dirt cheap. But if I have to Mod the 700 it might not be worth it......Tim