MONTE CARLO 700r4 swap 87 Monte

[Hamrtym2]

Good morning everyone! My 1987 Monte has been in the family since 92. We bought it with 56k miles on it. It still had the fully original drivetrain until I bought it from my dad. It had a 4.3 v6 fuel injected with a th200C 3 speed transmission. (MV9 code) I swapped the engine to a v8 carbureted 350 with a fuel pressure regulator etc. Ecm is still in the car for everything else but it doesn’t control the engine. Now I’m swapping to a 700r4 transmission and I’m also doing rear end but that isn’t the topic today. To swap to this 700r4 what do I need to know? Will I have to change the gear select cable and kickdown cable? I assume I can get a new transmission crossmember and I know I’ll need a new driveshaft. However the biggest concern and question is the 700r4 lock up. How would a guy wire up this lock up? I’ve heard guys say do it with a toggle switch but I really don’t want to have to deal with flipping a switch all the time. Did the 200C 3 speed have a lock up? If so then I’m assuming I could find that wire and use it. Either way, whether it did or didn’t, can someone run me through what I need to know for the lock up and the cables? It’s a column shift car. How would I identify if the 200c has a lock up? FYI yes it has a 200c 3 speed. Verified by the RPO sticker for proof. Had typical “fb mechanics” trying to argue with me that the 200C wasn’t factory and that my car must not be a real 87 even though the RPO shows a 200C 3 speed from factory with a 1987 vin number. 🙄

 

[ssn696]

Nice thing about the 4.3 is it came with a baffled tank to support its in-tank fuel pump. If you are not hot rodding the 350, you can swap the pump to support an EFI 350. Easiest option is to locate a 2wd 87-95 pickup with a 350/700R4 or an 87-92 disCorvette donor and use the heads and induction/injection plus harness and ECM. Make sure that your 350 is about the same compression ratio. There's a lot more involved, but that at least you heard about this option. The 700R4 has a low first gear, so you can use a high-2 series rear gear, or go to a 3.08 or 3.23 max gear set. Lower ratio will be wasted on a mild 350/700-R4.

 

[CopperNick]

Just so I am clear on this, you have already swapped in a 350 and it runs a carb. The current transmission is the 200R4 that was bolted to the 4.3 V6 that used to be in your engine bay. You want to swap out the 200 for the 700R4, that about sum up the situation?

Why? I do get that the TH200R4 has an apparent bad reputation as being a weak box but that is based mostly on people trying to make it do things that in street form it is not equipped to do. If your plan is a street cruiser then the 200 will work for you just as it is. If you need more ability from it, the parts do exist to build them up. And they do come with the lockup converter and the TVS cable.

As for the 700R4, it is based on the 350 case with an additional gear, meaning it is a 4spd of sorts, 4th being overdrive. It has the lockup converter and is TVS cable actuated. I've posted on this before but summarily, the lockup is immediately active. This means that as soon as you put the car in gear, the lockup solenoid for the converter is energized. What temporarily disarms it is applying the brakes. Why? because the brake switch on the pedal bracket underneath the dash is a 4 pin version, two for the brake lights and the other two for the converter. Simply put, apply the brakes and the converter disengages until the brakes are released and then it returns to being active. The harness for the converter circuit is a three wire with a dedicated plug that fits the socket on the drivers? side of the t-box. One wire is ground and the others are power to the switch to turn it off or on.

In terms of actual dimensions, Google can be your friend:


The TH-350 transmission has a total length of 27¾ inches and is 20¾ inches long from the front to the mounting pad. The TH-700-R4 transmission is 30 inches in total length and 22¼ inches from the front to the mounting pad. The 700R4 is heavier than the TH350, weighing 155 lbs compared to the TH350's 120 lbs.
https://www.onallcylinders.com/2015...apping-a-th-350-transmission-for-a-th-700-r4/
As provided by the "OnAllCylinders+2" website.


For you this means that yes, you would either need a new crossmember or have someone competent rework your existing crossmember to move the mounting pad to the back of the tube instead of the front. Probably simpler to score the new member particularly if you plan to go dual exhaust.
The driveshaft length might or might not change, for that you would need to slip the front yoke onto the output shaft and do a physical check. The good part is that the front yoke for the 700 is the same as that for a 350 and probably the 200 as well.

About the only value to this swap is that you get a deeper first, mostly because the 700 was geared to deal with the heavier B, C, G, and K series bodies.


Nick

 

[stew86MCSS396]

I’m gonna go with the OP knows what he has considering my 4.3L tbi is backed up by a 200c. If rpm and speed is the only thing that is needed to command the TCC then your existing wiring would be able to plug into the 700r4. This also assuming your cable drive and not using mag/tone wheel. My question would be is there anything wrong with the 200c bc if you smoked it with wrong line pressure then my guess is you’re going to smoke the 700r4 if you don’t address the correct geometry the tv cable needs.

 

[Hamrtym2]

Nice thing about the 4.3 is it came with a baffled tank to support its in-tank fuel pump. If you are not hot rodding the 350, you can swap the pump to support an EFI 350. Easiest option is to locate a 2wd 87-95 pickup with a 350/700R4 or an 87-92 disCorvette donor and use the heads and induction/injection plus harness and ECM. Make sure that your 350 is about the same compression ratio. There's a lot more involved, but that at least you heard about this option. The 700R4 has a low first gear, so you can use a high-2 series rear gear, or go to a 3.08 or 3.23 max gear set. Lower ratio will be wasted on a mild 350/700-R4.

I never knew about that baffled tank. That’s great to know because I actually need a new tank since my current one is still original and sat for 10 years plus the sending unit got stuck so my gauge doesn’t work. As for the engine, I’m not sure what you mean with that but it is already swapped. I found a 2010 crate 350 in a 96 Chevy that was in a local scrapyard. Don’t know that they knew what they had. Truck had 146k miles but the engine numbers came back to a 2010 crate 350 online. Because it was in a 96 k1500 it has vortec heads. I did a high pressure oil pump in it and tossed a mid range performer intake on it and a Holley 600 cfm carb. I don’t use the ecm for the engine. It sure woke up and is amazing even for a simple mostly stock mild 350. As for rear end, that’s definitely where I lack. I have never been able to really understand rear gearing. Currently it has something in the 2’s in it. I have a pic of the RPO sheet I suppose I can just toss that here. But I was thinking 3.55 or 3.73 posi rear. Or is this a bad idea?

 

[Hamrtym2]

Just so I am clear on this, you have already swapped in a 350 and it runs a carb. The current transmission is the 200R4 that was bolted to the 4.3 V6 that used to be in your engine bay. You want to swap out the 200 for the 700R4, that about sum up the situation?

Why? I do get that the TH200R4 has an apparent bad reputation as being a weak box but that is based mostly on people trying to make it do things that in street form it is not equipped to do. If your plan is a street cruiser then the 200 will work for you just as it is. If you need more ability from it, the parts do exist to build them up. And they do come with the lockup converter and the TVS cable.

As for the 700R4, it is based on the 350 case with an additional gear, meaning it is a 4spd of sorts, 4th being overdrive. It has the lockup converter and is TVS cable actuated. I've posted on this before but summarily, the lockup is immediately active. This means that as soon as you put the car in gear, the lockup solenoid for the converter is energized. What temporarily disarms it is applying the brakes. Why? because the brake switch on the pedal bracket underneath the dash is a 4 pin version, two for the brake lights and the other two for the converter. Simply put, apply the brakes and the converter disengages until the brakes are released and then it returns to being active. The harness for the converter circuit is a three wire with a dedicated plug that fits the socket on the drivers? side of the t-box. One wire is ground and the others are power to the switch to turn it off or on.

In terms of actual dimensions, Google can be your friend:


The TH-350 transmission has a total length of 27¾ inches and is 20¾ inches long from the front to the mounting pad. The TH-700-R4 transmission is 30 inches in total length and 22¼ inches from the front to the mounting pad. The 700R4 is heavier than the TH350, weighing 155 lbs compared to the TH350's 120 lbs.
https://www.onallcylinders.com/2015...apping-a-th-350-transmission-for-a-th-700-r4/
As provided by the "OnAllCylinders+2" website.


For you this means that yes, you would either need a new crossmember or have someone competent rework your existing crossmember to move the mounting pad to the back of the tube instead of the front. Probably simpler to score the new member particularly if you plan to go dual exhaust.
The driveshaft length might or might not change, for that you would need to slip the front yoke onto the output shaft and do a physical check. The good part is that the front yoke for the 700 is the same as that for a 350 and probably the 200 as well.

About the only value to this swap is that you get a deeper first, mostly because the 700 was geared to deal with the heavier B, C, G, and K series bodies.


Nick

You’re close yes. I just posted the RPO sheet on a reply of an earlier comment. So this car was a 4.3 fuel injected car. It’s now a 350 carb with vortec heads and a 600cfm Holley carb. It didn’t come with the 200r 4 speed. It came with the th200C 3 speed. Currently still has that 3 speed to this day. Now this 3 speed still works. However she’s tired. Especially after now being behind a 350 power plant. The tail shaft on it has TONS of play. So much so that it vibrates through the floor and the steering column at highway speeds. Grab the shaft and she’s loose inside that trans like a prom queen on prom night. That coupled with the fact it’s a 3 speed is why I’m changing. I’ve got a 700r4 I bought from a wrecked 2wd early 90s Chevy that a local older man owned. Truck it came from had 75k miles on it. So simply put, I chose 700r4 because I’ve had a firebird before with a 700r4 behind a mild built 305 and i was impressed believe it or not. Also because it currently doesn’t have a 200r 4 speed. It’s actually a 3 speed. RPO confirmed built with the 3 speed. To my understanding the 200c 3 speed already has lock up? Correct? I’m handy and decent at what I do but I’m no master mechanic here so if you’ve got a little more explanation for me of what to do for this then by all means dumb it down a hair for me. I do have my Haynes manual as well. So it should hopefully have wiring diagrams for the 200c in it

 

[Hamrtym2]

I’m gonna go with the OP knows what he has considering my 4.3L tbi is backed up by a 200c. If rpm and speed is the only thing that is needed to command the TCC then your existing wiring would be able to plug into the 700r4. This also assuming your cable drive and not using mag/tone wheel. My question would be is there anything wrong with the 200c bc if you smoked it with wrong line pressure then my guess is you’re going to smoke the 700r4 if you don’t address the correct geometry the tv cable needs.

No there’s nothing wrong with this 200c per se. so this trans is original for this car. It’s what? 38 years old? Roughly. So this trans has always been in this car behind the 4.3. The old girl had sat in storage for almost 10 years. Because that 4.3 kept blowing out. Went through 2 engines. Swapped it to the 350 v8 3 years ago. Granted I only have ran this car MAYBE 5-10k miles in the last 3 years. But that 3 speed trans is tired. It works, it shifts, it hasn’t left me stranded but she’s tired. The tail shaft has a ton of play in it causing a vibration. Plus the car gets terrible fuel economy with the 3 speed behind the v8. Basically she’s worn out and it’s time for a new one and I always figured in my mind that 350/700r4/3.73 would always be a solid set up. That’s why I chose 700r4. I’ve already got the 700 trans. Just need to figure out the details before I start tearing into it. How would I wire that lock up? I wouldn’t imagine they’d be the same plug. So I’d need to figure out what wires were for what and rewire a new plug?

 

[ssn696]

The 'Gxx' codes on the right side of the RPO tag will tell you what gear you have. Might be a 2.56. A better shot might help.

It sounds like you have the better 96+ 350 with the Vortec heads. Also nice because that engine is set up for a roller cam. If you swapped in any old HEI distributor, be careful, you need to swap the distributor gear so it does not grind down the cam gear. You could retrofit an aftermarket EFI setup on top. As you probably noticed, the Vortec block is usually not drilled for a mechanical fuel pump.

As to lockup, you can run without a computer using a pressure switch and vacuum switch. Painless sells a kit, or you might get lucky finding piece parts.

Thread '200-4R TC Lockup Kit - build your own'

Dec 26, 2015

I bought a 700-R4 lockup kit a while back. It uses a pressure switch that closes a circuit that applies current to the TC solenoid when it senses pressure on the 4th gear circuit. I would like to see if I can make this kit work on a 200-4R. The expensive 200-4R lockup kits put a switch on the 4th gear pressure channel on the valve body, inside the pan. Is there an external 4th gear pressure tap on the 200-4R? The 700-R4 4th tap is behind and below the 2-4 servo, although the later ones lack this and one is supposed to drill and tap the servo cover for 4th line pressure.

...

• ssn696
• Replies: 15
• Forum: Transmission / Rear End / Driveline

 

[CopperNick]

Okay, again, so what you have for a slush box is a three speed, interesting that, and it is tired. No, I really can't offer anything else beyond my initial comments. Mechanically it is straight forward swap. Mine, when I did it, was so straightforward in the nuts and bolt department that I got to use the existing ring gear from my TH350 and it mated to the 700's converter without issue. If you are worried about issues with the converter and ring gear match then you can pull the converter and do a test fit on the ring gear to see if it sits down against the mounting pads and the center pad indexes into the crank pocket. After that, be extremely careful when you re-install the converter, apply a little grease to the converter snout so that when it slides back onto the input shaft, the seal in the front pump cover will let it pass a little easier and more safely, and don't forget you will feel or hear three distinct, "clunks" as the teeth inside the snout line up with their matching drive surfaces. If you got it right, the last clunk will leave the converter sitting lower than the face of the t-box bell housing by +/- about 3/8ths of an inch. Not an issue, supposed to fall that way, and once you have the bell housing to block bolts run down and tight, then you can slide underneath and, if all is still well you can ease the converter forward and gently spin it to get the ring gear to converter bolt holes to line up with the bosses on the converter face. For the 700, be aware that the bolts I just mentioned might have to be metric, or not, again checking the threads on the converter while the box is on the stand or floor is something to consider; the box to block bolts ought to be USA WMN, aka 3/8th UNC, about 1-1/2 inch long. I actually had a grade eight capscrew snap on me during the last pass with the torque wrench when I was running down the bell bolts so mine are ARP fasteners and I went with their spec for torque. Most folks tend to go with the "Three grunts and a fart" cumulative torque value. Up to you.

Last thoughts... take your time, don't try to force things together that don't seem to want to be happy campers, use lock-tight if you think it is necessary, and be on the lookout for a Chilton Manual for your vehicle. written and published in the USA, more detail and arguably more comprehensive. After that, you can still get copies of the factory service manual if you do some on line digging. I've personally found Haynes to be useful but sometimes vague on vital details or information.



Nick

 

[ssn696]

If you proceed with the plan just mentioned, replace the pump seal and the rear main on the engine. Easy, since it's a one-piece. Then you have less to leak. The flex plate on the engine will match the 3-bolt pattern on the converter. If you modify the 700-R4 with the lockup conversions, recommend new filter and gasket while in there. The yoke will be the same, but you'll need to shorten the driveshaft. I may have one that I had built, but is not the right length - measure and let me know if useful. I hope you got the throttle valve cable with the trans. These are non-existent new anymore. I also hope you got the bracket for it that bolts to the manifold. Getting alignment is a bit of a trick. Revisit the Forum later and it will abide.