700R4 Information Thread

[Ricko1966]

On my R4 I have lockup on a switch and it does the job.
I know there is a way to add in pressure switches and daisy chain them to lock and unlock on its own. Do you or someone else on here have a wire diagram for this so I can make my own harness?

It easy there's already a 4th gear pressure switch in the pan in the valve body. Supply 12v to the transmission,use the existing 4th gear swich to turn on and off the lockup solenoid. Just look at the 4th gear switch as if it was a toggle switch that turns on the lock up solenoid in 4th gear. Interrupt the 12v supply with a toggle if you want the option of disabling lock up.

 

[Rkendrick05]

Looks like the 3/16 plate and a couple new holes is going to be the way to go.

 

[mibars]

Maybe an unusual question, but do you know what's the volume of fluid pumped by the oil pump in this transmissions?
It's just out of my curiosity to undersand how the auto transmissions works and how efficient it is. By knowing volume and pressure (and pump efficiency) a hp loss can be calculated .

 

[NickTransmissions]

Maybe an unusual question, but do you know what's the volume of fluid pumped by the oil pump in this transmissions?
It's just out of my curiosity to undersand how the auto transmissions works and how efficient it is. By knowing volume and pressure (and pump efficiency) a hp loss can be calculated .

I don't but maybe others on here do...You can also contact Dana Wilkes at Probuilt Automatics to see if he knows or the folks at Automatic Transmission Service Group. It's def something the GM Powertrain engineers would be in a position to answer but I have no idea who they are or how to contact them.

 

[1979 K10]

Hi all,
I just picked up a '86 Blazer Custom Deluxe with the ESC LE9 305 v8, 700R4 and 3:73 gears NP208. It has 180 - 200k on it, prior owner wasn't sure of exact milelage but said PO 10 years ago owned a transmission rebuild shop. I noticed the truck shifted very firm when driving around normally. Wide open throttle shifts felt normal not hard shifting. I checked the TV cable and it was so tight that it was limiting full throttle on the OEM 4bbl quadrajet carb. I tried using the auto adjuster on the TV cable but it won't auto adjust unless I press in the button and then WOT. Doing this with the button pressed in makes the TV cable too loose and it wont downshift as expected at half and full throttle. I ended up manually adjusting the TV cable so it is almost as tight as before but I can now get full throttle from the carb. I went on a test drive and the trans still shifts firm. It does downshift as expected, drops 1 gear at half throttle and drops down again at full throttle.

I dropped the pan and the fluid was very dirty, lots of grey in the fluid but the bottom of pan was clean with only grey material on the magnent. Fluid didn't smell burnt just old and dirty. I cleaned the pan, replaced filter and flushed out 3-4 gallons of ATF by disconnecting the lower cooler line at the radiator and running the engine in park to pump out old fluid until I see it was getting cleaner.
Truck shifts the same with new, clean Maxlife ATF. I don't feel the torque converter locking up and there are no vacuum lines going to the 700R4. Maybe I don't have the lockup version?

I am going to add an external cooler to the trans along with the radiator cooler. Does anyone know the thread size at the radiator and cooler lines? I was going to get adapters to convert trans line to hose barb fitting and radiator output to hose barb fitting.

Also going to add a temp sensor, was going to use the pressure test port for the sensor. I see two plugs on the side of the transmission passenger side...

 

[NickTransmissions]

Hi all,
I just picked up a '86 Blazer Custom Deluxe with the ESC LE9 305 v8, 700R4 and 3:73 gears NP208. It has 180 - 200k on it, prior owner wasn't sure of exact mileage but said PO 10 years ago owned a transmission rebuild shop. I noticed the truck shifted very firm when driving around normally. Wide open throttle shifts felt normal not hard shifting. I checked the TV cable and it was so tight that it was limiting full throttle on the OEM 4bbl Quadrajet carb. I tried using the auto adjuster on the TV cable but it won't auto adjust unless I press in the button and then WOT. Doing this with the button pressed in makes the TV cable too loose and it wont downshift as expected at half and full throttle. I ended up manually adjusting the TV cable so it is almost as tight as before but I can now get full throttle from the carb. I went on a test drive and the trans still shifts firm. It does downshift as expected, drops 1 gear at half throttle and drops down again at full throttle.

I dropped the pan and the fluid was very dirty, lots of grey in the fluid but the bottom of pan was clean with only grey material on the magnent. I cleaned the pan, replaced filter and flushed out 3-4 gallons of ATF by disconnecting the lower cooler line at the radiator and running the engine in park to pump out old fluid until I see it was getting cleaner.
Truck shifts the same with new, clean Maxlife ATF. I don't feel the torque converter locking up and there are no vacuum lines going to the 700R4. Maybe I don't have the lockup version?

I am going to add an external cooler to the trans along with the radiator cooler. Does anyone know the thread size at the radiator and cooler lines? I was going to get adapters to convert trans line to hose barb fitting and radiator output to hose barb fitting.

Also going to add a temp sensor, was going to use the pressure test port for the sensor. I see two plugs on the side of the transmission passenger side...

No vacuum lines should be going to the transmission as the 700R4s use a throttle valve system to manage/regulate line pressure inside the unit whereas the previous generations of transmissions (TH350/400, etc) used vacuum modulation for the same purpose.

Based on your description of it's shift firmness, I'm guessing it was set up for a higher stall torque converter relative to what you have in it now or someone was overly aggressive in the feed orifice resizing in the spacer plate...For you to confirm or deny, you'd have to drop the pan and remove the filter, valve body, rev hold down plate and separator plate then take a picture of it, post it here for us to see how the feed holes have been drilled.

The more concerning issue is the lack of TC lock up...If the truck is stock, there should be a small wiring harness going to the transmission, plugged into the square case connector on the side. If this is not so, you will need to make it functional again...Given you have an 1st generation 700R4, you have two options:

1. Drop the valve body and locate the TCC control valve train (4th valve train to the right of the 1-2 shift valve train) and see what is in that bore...If there are two aluminum slugs, remove those and install a mechanical torque converter clutch lock up kit...They are available from Superior Tech or Transgo - here's Transgo's version.

2. Install an internal-external torque converter clutch lock up kit - you don't have to drop the valve body for this one but you will have to do some external wiring as well as install the internal wiring harness that comes with the kit...Many of my customers like the Painless Performance LU Kit.

You need to do something ASAP before you overheat the unit, burn the converter clutch and destroy the front clutch packs (forward and 3-4 clutch) in the transmission.

Lastly, you need to use a transmission pressure gauge to validate that your TV cable adjustments were done correctly...Read these instructions for details.

Let us know if you have any questions.

 

[1979 K10]

Thanks for all the detailed information Nick! I have a tachometer on order and will need to rent or by a pressure gauge. The K5 Blazer was driven fairly regularly by the old guy I bought it from for 20k miles over 10 years and he said he never touched the transmission. It drives fine with no slippage and shifts through all the gears. I'm familiar with what TCC lockup feels like on my 97 k1500 with 4l60, I can feel it and see the rpms drop on the tach. On the K5 there is a vacuum switch on the firewall above the transmission dip stick. Does this affect torque converter lockup?. I'll see what that goes to. I'm not by the truck now but will look for the electrical connector to the transmission. You are saying the TCC should lock up in 4th and 3rd automatically or just 4th?

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[NickTransmissions]

@1979 K10 - Factory lock up strategy for your year/model has the TC clutch applied in 3rd and 4th gear however if someone modified the lock up via a toggle switch, I suspect they intended for it to activate the TCC in 4th gear only and only when they flip the switch...So if that's the case (you will need to confirm or deny as we aren't there w/the vehicle) and you don't want to have to remember to flip the switch each time, follow one of my two recommendations above.

BUY (NOT RENT) - BUY a transmission pressure gauge...IF you own a vehicle equipped with a TV-based transmission, having that tool is what I would consider a mandatory part of your tool kit (unless you want to out-source the sustainment/maintenance to a shop, which will cost you a lot more than a $50.00 gauge).

 

[1979 K10]

$40 isn’t bad. I’ll buy one. Reading through the pressure check procedure you keep engine at 1k rpm and check pressures with the cable in its normal min position and then manually pull the cable but leave throttle at idle yes?

There is no manual lockup switch in the cab, it once had a trailer brake controller that is long gone but everything else wiring wise is original factory.

It doesn’t say if I can test at cold temperatures or if I need to get transmission up to normal operating temp.

 

[NickTransmissions]

$40 isn’t bad. I’ll buy one. Reading through the pressure check procedure you keep engine at 1k rpm and check pressures with the cable in its normal min position and then manually pull the cable but leave throttle at idle yes?

There is no manual lockup switch in the cab, it once had a trailer brake controller that is long gone but everything else wiring wise is original factory.

It doesn’t say if I can test at cold temperatures or if I need to get transmission up to normal operating temp.

Test at operating temp as colder fluid may throw inaccurate readings. Yes, min and full TV at 1000 RPMs....You should see fast and/or instant line pressure rise going from minimum to full TV on the cable. If you don't see any line rise, you'll need to begin the trouble shooting process - we'll cross that bridge if we come to it.

 

[RetroC10Sport]

After a fluid change, I lost 4th gear. 1989 GMC, 1987 L98 TPI 350, 1991 Caprice 700r4. I did a fluid change 3 months ago, did not touch anything but the pan and filter. That day I had 4th before the change, I took it out the next day and noticed I only had 1st, 2nd and 3rd. I didn't use any RTV on the gasket. I used Mercon V fluid which is what i put in it when I put the trans in about 4 years ago. Fluid wasn't burned and there wasn't any crap in the pan when I changed it, it was just old.

I only use 4th maybe 3 times a year, otherwise it's just city driving and I leave it in 3rd for that. Should I adjust the TV cable again though I never touched it? What should I look for? Thanks y'all.

 

[NickTransmissions]

After a fluid change, I lost 4th gear. 1989 GMC, 1987 L98 TPI 350, 1991 Caprice 700r4. I did a fluid change 3 months ago, did not touch anything but the pan and filter. That day I had 4th before the change, I took it out the next day and noticed I only had 1st, 2nd and 3rd. I didn't use any RTV on the gasket. I used Mercon V fluid which is what i put in it when I put the trans in about 4 years ago. Fluid wasn't burned and there wasn't any crap in the pan when I changed it, it was just old.

I only use 4th maybe 3 times a year, otherwise it's just city driving and I leave it in 3rd for that. Should I adjust the TV cable again though I never touched it? What should I look for? Thanks y'all.

Loss of fourth gear / falling out of fourth can indicate burning/heavily stressed 3-4 clutch pack. Fluid-wise, you can use DexMerc, Dex6 or Dex Multi-blend fluid. Ive never used Mercon V, which is for Ford units but cant say it's bad/harmful...

Do a line pressure test and let us know the results and we can go from there.

 

[bucket]

Loss of fourth gear / falling out of fourth can indicate burning/heavily stressed 3-4 clutch pack. Fluid-wise, you can use DexMerc, Dex6 or Dex Multi-blend fluid. Ive never used Mercon V, which is for Ford units but cant say it's bad/harmful...

Do a line pressure test and let us know the results and we can go from there.

Is Mercon V the equivalent to the old type F fluid?

The guy that ran the trusty trans shop I used to go to, told me about 25 years ago that I could use it to slightly firm up the shifts. Similar to running the B&M Trick Shift fluid.

 

[NickTransmissions]

Is Mercon V the equivalent to the old type F fluid?

The guy that ran the trusty trans shop I used to go to, told me about 25 years ago that I could use it to slightly firm up the shifts. Similar to running the B&M Trick Shift fluid.

I think it is; if so, it should yield slightly firmer shifts using clutches/bands designed for Dextron, as he mentioned...

 

[RetroC10Sport]

Loss of fourth gear / falling out of fourth can indicate burning/heavily stressed 3-4 clutch pack. Fluid-wise, you can use DexMerc, Dex6 or Dex Multi-blend fluid. Ive never used Mercon V, which is for Ford units but cant say it's bad/harmful...

Do a line pressure test and let us know the results and we can go from there.

Thought Type F was for Ford? It might be Dex6, I'd need to dig out the jugs.

I don't have the tools to do a pressure test. I don't see how a fluid change can stress the clutch pack when it was fine not 6 hours before and I don't smell burned fluid before or now.