700R4 Transmission Questions/Issues

[Burbinator86]

Hello all. I’m new to the forum and new to Squarebodys. I have a 1986 GMC Suburban K1500 with a 350 and a 700R4. I’ve had it roughly 2-3 months and it hasn’t been a daily running rig in 15 years (not my doing).

I bought it and got it to running and driving shape but im having some issues that I need help with. Before I get into it i’ll mention nothing Tranny related has been touched besides filling the ATF back up and replacing the tv cable.

The issue: When I drive it, it seems to rev a little high before shifting. Granted I don’t have a Tach but I’d Guess-timate around 2500-3000 rpm. It shifts 1-2 at around 15mph, 2-3 at 25, and haven’t tried fourth I don’t want to damage anything. Added to that is it seems to shift really soft. Like almost not able to tell it’s shifted at all. More between 2-3 than 1-2. And this is light-moderate on the throttle in speed limits 30 or less.

And when I go to look at adjusting the TV Cable, it’s to the point of no more adjustment (pulling it out). I have the Edelbrock TV Cable mounting bracket on my 1406 carb.

My thoughts on what it could be is:

Something related to the TV Cable? A vacuum line issue as some little ones are disconnected?

Any help is greatly appreciated.

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[Ricko1966]

Hello all. I’m new to the forum and new to Squarebodys. I have a 1986 GMC Suburban K1500 with a 350 and a 700R4. I’ve had it roughly 2-3 months and it hasn’t been a daily running rig in 15 years (not my doing).

I bought it and got it to running and driving shape but im having some issues that I need help with. Before I get into it i’ll mention nothing Tranny related has been touched besides filling the ATF back up and replacing the tv cable.

The issue: When I drive it, it seems to rev a little high before shifting. Granted I don’t have a Tach but I’d Guess-timate around 2500-3000 rpm. It shifts 1-2 at around 15mph, 2-3 at 25, and haven’t tried fourth I don’t want to damage anything. Added to that is it seems to shift really soft. Like almost not able to tell it’s shifted at all. More between 2-3 than 1-2. And this is light-moderate on the throttle in speed limits 30 or less.

And when I go to look at adjusting the TV Cable, it’s to the point of no more adjustment (pulling it out). I have the Edelbrock TV Cable mounting bracket on my 1406 carb.

My thoughts on what it could be is:

Something related to the TV Cable? A vacuum line issue as some little ones are disconnected?

Any help is greatly appreciated.

Pic is for attention.

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Do you have a correction arm on the carb,and the correct bracket on the manifold?

 

[Turbo4whl]

I am not the 700R4 guru, but getting the throttle valve cable adjusted correctly is very important. Since you are running an aftermarket carburetor it might be harder set correctly. Geometry of the throttle linkage and the cable mounting distance may not be the same as the factory quad.

This may not work for you, but to get the right cable pull on the Holley, I added a crimped on spacer to keep the cable adjuster in range. You can see it on the end of the cable. I will add, this took several attempts with different length spacers to get it right.

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[Broken85]

Don't drive it if it is slipping until you pressure test the transmission to dial in the TV cable. You will burn up a 700R4 in a few miles if the TV cable isn't right. Was it acting this way before you replaced the TV cable or just afterwards? Adjusted all the way out is also probably not helping. Adjust it inward for firmer shift points, full extended is probably contributing to, or is the problem. A pressure test kit is like $30 on Amazon.

Check out Nicks' thread for everything 700R4. He is brilliant with these transmissions.

700R4 Information Thread

Hello All, Thought I would start an all-encompassing 700R4 information thread since so many of our trucks have one of these transmissions installed. Please feel free to add your own tips, tricks and anything else that you found helpful or ask questions as you need to and I’ll respond as soon as...

www.gmsquarebody.com

Nick also provided great instructions to get a pressure test done.

https://static.summitracing.com/global/images/instructions/bmm-9500377-04.pdf

 

[PrairieDrifter]

Mine wants to "self adjust" to almost all the way out. But I'm reality it really wants to be adjusted with like 1/2 inch of stickout with my new Holley and cable. Quadrajet was also 1/4 to 1/2 inch. Self adjust feels like a total dog and barely feels like a shift, more like an rpm change lol. For sure not good.

Feels pretty good. I did mine without a gauge for the first 40,000, was definitely a little loose 1-2 was soft on hard accel. Replaced cable, still didn't cough up for a gauge lol, feels way better up high now, proper shift points on light accel. I don't want my 700 to die necessarily but I also wouldn't be sad if it did. It's the one from when I bought the truck 12 years ago. Blows me away it's made this far on a big tire truck. 50-60,000 on it since I had big tires and messes with the odometer.

Not condoning no gauge, but if you know what it should feel like then you can get pretty close. Tighter is better than loose. Would definitely not recommend for a fresh built trans full of money.

 

[Burbinator86]

I appreciate your guys‘s input. I adjusted the cable again and now it shifts great on acceleration but now it won’t kickdown or downshift at all.

Before the new cable was installed, the old one was frayed and it wouldn’t upshift, but kickdown was great. It’s like the exact opposite.

 

[Burbinator86]

Do you have a correction arm on the carb,and the correct bracket on the manifold?

I do have the Edelbrock correction arm and the bracket is stock. My Suburban is factory with the 700R4 and the bracket is stock as well.

 

[Burbinator86]

Another update: No matter what adjustment I seem to do it won’t kickdown. If I mash it hard it’ll seem like it’s kicking down and rev high but slip like crazy. Doesn’t matter if it’s 4-3 or 3-2. As previously mentioned it didn’t do this before. And yes the cable is connected in the transmission.

Could it be a governor? I don’t have money to fix this and im struggling with it.

 

[Broken85]

Bru, I hate (really hate) suggesting this, but you may have burned the clutches out of it already with that cable being so loose. Drop the pan and see what the fluid looks like for a cheap di-ag and the coat of a $30 filter and gasket kit. If it is cloudy and gray and a bunch of gray mud in the bottom of the pan, that is probably the verdict. It only takes a few miles with a 700R4 to ruin your day if that cable is adjusted wrong.

Hoping the fluid is still ruby red for you.

 

[Burbinator86]

What would happen if the TV Cable at the transmission side was hooked up to the wire properly but wasn’t sealing well with the rubber gasket?

 

[Ricko1966]

What would happen if the TV Cable at the transmission side was hooked up to the wire properly but wasn’t sealing well with the rubber gasket?

The only symptom would be a small fluid leak.

 

[Burbinator86]

The only symptom would be a small fluid leak.

Yeah I kinda figured. I just checked and it’s fine

 

[PrairieDrifter]

The only symptom would be a small fluid leak.

It's actually a big fluid leak lol. If the seal is junk, it'll weep. But if it's not seated right it'll POUR fluid on the ground. Ask me how I know lol.

Still drove the same though.

 

[Burbinator86]

As odd as it is… the rig did sit for 15 years and it could be kinda stuck/dry/goopy in the transmission. I’m gonna keep driving it and if it doesn’t get better I think it’s the valve in the transmission. But im seeing minor improvements with each drive.

PS: it does manually downshift just fine and kicks down occasionally now

 

[idahovette]

Haven't read the whole thread, but have you dropped the pan and changed the filter and filled with new fluid?