700R4 Revisited

[rockman20]

Okay, I posted on here a while back about my problems with my 700R4 and the torque converter locking up too early. With the gear selector in 3rd, you can feel the 1-2 shift, the 2-3 shift, and then just after that is when you can feel the converter lock and it bogs the engine down.

Keep in mind that this is a 82 Scottsdale K10 that originally had the 6.2L diesel and now is housing a Chevy 350.

Transmission shops told me it was the TV cable. The TV cable that was on there definetly was screwy so I bought one for that truck. Well, it doesn't fit. I don't know if the 350 has a different mount then the diesel does or what, but there is bracket that is bolted to the last two bolts on the back of the intake on the drivers side. This is the bracket where the TV cable goes, but if I put it there, the cable will not reach the clip on the carb. So I am going to custom make a new bracket for this, not that big of a deal.

But I rigged up a setup to hold the TV cable closer to the carb, got everything hooked up, adjusted the cable just so you can get the carb WOT and took the truck for a spin. The shift points changed, but the damn converter still locked at about 30.

So I know that there are 2 transmission shops I am not going to because they both told me it was just the TV cable.

Someone out here must know what all is different between a transmission behind a diesel and one that is behind a gas. Is it just the converter that is different or is there a difference in the valve body also? Anything else?

[arveetek]

The diesel engines use a Throttle Position Sensor mounted to the side of the injection pumps to control the TC lockup. That way, when the the throttle is depressed, the TC will unlock. I'm not totally sure about gassers, but I believe they use a vacuum switch to control the lockup function. I'll bet that when your gasser was installed, they simply directly wired up the TC to lock as soon as it goes into third.

You'll need to find out how the gasser setups are actually wired for the TC controls.

Also, diesel 700's use a different governor than gassers, so in order to get the shift points correct, you'll need to change the governor. Otherwise, it will shift too soon, no matter how much you fiddle with the TV cable.

[arveetek]

Oh yeah, the valve bodies are the same for gasser and diesel 700's. Only the convertors and governors are different.

[rockman20]

Exactly the info I was looking for. I figured the converter was different, but wasn't sure if the valve bodies were. One transmission shop claimed that he had added a tighter spring on some valve and that should of changed the lockup point but it didn't.

Now I will show my colors on how A/T illiterate I am. How hard is the governer to replace? Do you just drop the pan or do you have to remove the valve body?

And then a rough estimate on price for converter and governer.

Thanks again arveetek! Greatly appreciated!

[79BIG10]

To wire up the lock up converter the way Casey was talking about on a gasser look here http://www.73-87.com/garage/lockup.htm

[arveetek]

The governor is easy to change. You don't even have to drop the pan. It is located on the driver's side of the tranny, towards the rear, under a large round metal cap that is just pushed on. Some may have a wire clip holding the cover on, mine doesn't. Take a flatblade screwdriver and pry the cover off. A little fluid will come out, don't worry. You will see the governor staring at you. Pull straight out on it. It will have metal weights on one end, and a plastic gear on the other. Install the new governor, push the cap back on, and you're good to go. Piece of cake.

I ordered a replacement governor from here:

They show a "700-R4 Govenor assembly GAS # 35890" for $20.58

You can find it by clicking on "parts by transmission", then choosing "General Motors," and then choosing "hard parts" under the 700R4 column.

[arveetek]

I don't know if I'd bother with changing the convertor or not. The diesel unit is a heavy duty model. They usually have six bolts holding it to the flexplate instead of the typical 3 bolts found on gasser models. However, the diesel models do have a little lower stall speed. That's up to you to decide.

[rockman20]

Awesome responses so far. I've got the links bookmarked for all of this.

arveetek, if I change out the governor, would that change the lockup state of the converter? Or would that just change my 1-2 and 2-3 and 3-4 shift points?

The shifting doesn't bother me too much it's just that lockup at 30 that bothers me.

I haven't checked to see if the person before me did anything to the convertor as far as the lockup goes. I do like the idea of the beefier convertor since I do plan on putting a big block under the hood some day.

I was talking to a friend of mine last night about this problem. He said something about how the transmission shop rewired his 200R4 in his Monte Carlo when he eliminated the computer. He said that they had the ability to wire it to lock up at any RPM they wanted. They had set his up to about 2800. How would they of done that? With the setup like in the link that 79Big10 gave?

Thanks again for all the advice and generous info! The transmission is a hazy area for me and OD I am just plain in the dark on!

[arveetek]

The governor will only affect the 1-2-3-4 shift points. However, as a result of moving the shift points up a bit, the TC won't lock up as soon.

My advice would be to follow the instructions in that link Brandon gave you. That's what I did to my 700 when I installed it in my truck. Mine only locks up in 4th gear. I think that's why yours is bogging down, because it locks up in 3rd as well.

I just bought a kit from a local speed shop when I did mine. It had all the parts listed in that article. It was really quite simple to install.

I am going to be modifying my TC wiring soon. I want to install a manual switch so that I can lock the TC in 2nd and 3rd only when I want to, such as when towing my fifth-wheel. I have a 29' fifth-wheel, and when I'm pulling it down the road, I have to leave it in third most of the time. Locking up the TC in 3rd in this case would be a good thing. It would lower my rpms, and lower the heat inside the tranny.

But for everyday driving, only locking in 4th is the way to go.

I don't know how that shop you mentioned setup the tranny to lock up at a certain rpm. That's a new one for me. The article Brandon gave you shows how to wire up the tranny so that it will lock up as soon as it goes into 4th gear, regardless of engine rpm.

[rockman20]

Thanks again for all the advice. I am going to do the govenor first. Get that out of the way and then grab the supplies I need for the TC portion of it. I think that while I am doing it, I may just wire in a bypass switch as well. There are times that I have experienced where 3rd gear and a locked converter would be nice. Bucking a high wind while pulling a tandem axle car trailer for example.

Great information! Hopefully I can start on this project next week. The govenor I will attempt this weekend if I am not in the field and I will get or order the parts to do the TC portion at that time as well. (local GM dealer. Slightly higher then the page you recommended on the govenor, but they have the part on hand and no shipping charges so it basically equals out.)

Thanks again everyone! Next project after this will be the search for the big block to start rebuilding. "There is no replacement for displacement".

[Ol' Grey]

Originally posted by rockman20
I was talking to a friend of mine last night about this problem. He said something about how the transmission shop rewired his 200R4 in his Monte Carlo when he eliminated the computer. He said that they had the ability to wire it to lock up at any RPM they wanted. They had set his up to about 2800. How would they of done that? With the setup like in the link that 79Big10 gave?

I'd be willing to bet that it was done with an RPM activated switch similar to this

[swervin ervin]

Casey,

I'm not so sure locking in 2nd and 3rd is a good idea. As you know, the early 700R4's were junk. I think partly because they locked in 3rd too. One of the biggest things that kills these things is going in and out of lock. Again, as you know, you can't tow in OD because of this. If it locks in 3rd and starts locking/unlocking, it's a bad thing. Of course if you put a switch, it won't unlock once it's locked anyway. This may work out to be a good thing for you and the diesel.

I want to add, that the governor only controls WOT shift points. It won't change you normal driving shifts, or at least not enough to be able to tell. Your normal shift points are controlled by the TV cable. That's why it's called a TV cable, it moves the throttle valve in the valve body to control line pressure, and thus control when it shifts.

I would for sure get rid of a diesel converter when using it in a gas truck. I'm not sure, because I don't know, but I would guess it has a very low stall speed. This is bad for performance, good for towing and diesels. I bet that thing stalls at 1200 to 1400 rpm. If you go with a bigger motor and cam, you won't be able to hold it still at stop lights. Personally, I would go with something in the 2400 rpm range on my converter, but this is determined by gears, cam, vehicle weight, etc. You will not like a diesel converter for sure.

[arveetek]

Rockman,

Big block? Whaddya talking about? You need a high performance diesel man! I can show you how to build a 300 hp, 500 torque 6.5L turbodiesel that will bolt right in! Plus, you can get 20 mpg with it at the same time! Your truck started out in life with a diesel, why not restore it to it's former glory?

Mike,

I'll have to respectfully disagree with you. The governor WILL affect shift points below WOT. I bought an '86 Suburban with a 6.2L and 700R4 a while back. The tranny had just been rebuilt. No matter how much I adjusted the TV cable, the tranny would not shift right. It wouldn't go into overdrive unless I was doing at least 55 mph (3.73 rear). My other truck with a 700 would shift into OD at 35 mph (4.10 rear) if I let it.

After doing some research, I decided to pull the governor. Turns out that the rebuild shop installed a v-6 gas governor instead of the diesel one. I installed the right governor, and without any other adjustment, the shift points came right down. It would then shift into OD at 40 mph. Of course, I had to readjust the TV cable to get it just right. So the governor will affect shift points at all throttle positions.

Since the gasoline governor would not allow the diesel tranny to shift right, it stands to reason that diesel governor would not allow the gasoline tranny to shift right either.

I have the updated, 1990 model 700 in my '81. I only plan to manually lock the TC when holding it in gear, such as going up a hill. From other reading I've done, people who installed transmission temp guages have recorded that locking up the TC instantly lowers tranny fluid temperature, which will extend tranny life. I agree that constant locking and unlocking can harm the tranny. I just want to lock it while making hard pulls or leaving it in direct gear. I plan to install a tranny temp guage as well, so I'll let ya'll know what I find out firsthand.

I really don't have any idea what the stall speed for the diesel TC is. It is lower, but I've never been able to find a definite answer. Switching to a higher stall speed will definitely improve performance on the gas engine.

[swervin ervin]

I stand corrected.

I know when trying to up my WOT shifts with the tranny in drive or OD, I played with the weights a bunch. I bought a governor spring and weight kit. It had several different combinations you could try, and their suggested shift rpm. Well, let's just say, their suggestions were bunk. You can't have one group of weights and springs work at a specified rpm on every vehicle. Different vehicle weight, engine torque, etc., will change this. I got so tired of messing with this thing. I bet I pulled the cover 20 times or more. Finally after many different combinations, I ended up with a 5500 rpm WOT shift.

But you know what's funny, it never shifted at weird times or late/early during normal driving. Only thing that changed much for me was WOT. I did have to fiddle with the TV cable some at each setting to make it change right though. I guess they work together to a point.

I would be willing to bet money the diesel governor won't work at all in a gas engine, or at least would change at 2000 or 3000 rpm. Just find one out of a V8 gas truck. As a side note, a V6 governor will raise the rpm a bunch on WOT shifts. It all has to do with the amount of torque the engine has as to what governor weights and springs were used.

[apstguy]

RockMan, you got me thinking about mine. I noticed that mine shifts into 4th gear at 30 MPH if you drive normally (not aggresively). How can you tell if it locks up? I shifted between (D) and D and it made no difference! WTH? In drive it acts just the same as in overdrive. Don't bother me, but why is it doing this? My engine doesn't bog down like yours.

[arveetek]

Tyler,

You should be able to tell if your TC is locking up by driving about 50 mph or so in OD, and then lightly touching the brake pedal while holding the accelerator constant......keep a load on the engine, don't let off the throttle. Just don't hold the throttle down so much that it downshifts. You should be able to hear the engine rpm jump up a bit when the TC unlocks. When you release the brake pedal, the TC should lock again and the engine rpm will go back down. That is how it is supposed to work, unless the brake pedal switch has been bypassed.

Mike,

Yeah, after I posted last, I got to thinking about how much difference there would be between the v-6 and diesel governors. They're on totally opposite ends of the spectrum. There probably isn't as much difference between the gas v-8 and diesel governors, but I'd bet it's still enough to be a pain. The 6.2L has a redline below 4000 rpm....supposed to be about 3600 rpm, but it varies from engine to engine depending on where the injection pump was set to.