700r4 lockup issues. Trans back in

[KirsL]

OK so I've been trying to figure out why my truck lost lockup the last longer drive I took it on. So little back story.

Since moving to Florida the truck hasn't been used much as it didn't have a/c and was having fuel delivery issues. So I get both of those sorted out, new fuel tank and finish vintage air install, she should be good to go. Date night the the gf and I, I decide we'll take the stepside, only going 18 miles round trip. Will be a nice easy run for her. The drive to dinner everything is good. Part of the drive is at 55 mph, the rest around 30. The drive home was fine till on the 55 part, about a minute or so after hitting lockup two things happened. The hot pipe on the intercooler blew loose. Which made me dump the throttle for a moment. When I got back into I noticed it wasn't in lockup. Limped it the rest of the way home.

Once home fixed the intercooler pipe, had to weld a lip on it to hold the hose. Started looking in the lockup issue. Checked wiring outside of Trans and everything seems fine. Installed a temporary switch to mimic the lockup signal and have 12 volts to the trans. Took her for a test drive with the switch installed. Trans shifts good through all 4 gears just no lockup.

Decided to drain the fluid. Fluid smelled ok, had a normal amount of clutch material in it nothing crazy. Checked the lockup solenoid, has power to it, it seemed weak so I changed it since it was pretty cheap. Put some new fluid in and test drove again. No change, shifts good but still no lockup.

So now what? I'm kinda thinking the tcc is gone, but I'm not sure and don't want to change it as a guess. So I drained the pan again and I want to check the two I'm guessing pressure sensors. They have power to them but I'm not sure how to test them beyond that.

I'm thinking I may have to dig deeper into the trans but I need to be super money cautious since I'm between jobs at the moment. So I do have time to test stuff out.

Sorry for the long read. Thanks for any help.

 

[Blue85]

Is it an '82 trans? I can see the torque of a 6.5TD wiping out the TCC, especially if it spent time with the wrong gears and is high mileage. Of course you want to check everything else out first. Did you verify that the wiring inside the transmission is all good? If so, you can check for 12V on the transmission connector and verify that your vac switch, brake switch, etc are supplying power.

Here's a thread I posted some diagrams in: https://ck5.com/forums/threads/700r4-lockup-help.326424/ You can figure out which of the 3 switches yours doesn't have.

 

[Greg Ducato]

Try swapping the red connectors with the blue, the blue are currently on the 4th pressure switch, the red are on the 4-3 pulse switch. You want the solenoid energized through the 4th pressure switch. There should be 12 volts at the A terminal of the case connector.

 

[KirsL]

Ok, so here's what I've got so far. Truck has cruise control though not working it still has both brake switches. Brake light one works as it should, power passes when the pedal is pushed. The cc one has power with key on to one terminal but not the other, should be right?

My temporary switch is hooked into the green wire going to the trans, yet when I energize it both wires at the trans plug have power. Does confirm I have power at the trans though. I switch the wires like you said Greg and now the lockup solenoid doesn't click soon as it has power. The pictures shows how it's been hooked up since install.

Unless there's something else to check in the pan. I need to get some fluid so I can test drive it.

Side note, the truck is a factory 6.2/700 setup. This trans was first behind the 6.2 with stocks axles and gears. I put the 6.5 in after I lifted it. So with the bigger motor it's always had 4:56s with 35s. Trans is just a basic jasper rebuild. It only has about 8,000 miles in 16 years . Sadly the truck sat a lot as I had either time or money to work on it.

Thanks

 

[Greg Ducato]

With it hooked up through the 4th gear pressure switch as prescribed the solenoid will not be energized till 4th gear is applied and the switch contacts close.

 

[KirsL]

With it hooked up through the 4th gear pressure switch as prescribed the solenoid will not be energized till 4th gear is applied and the switch contacts close.

So if the tcc isn't toast it'll only lockup in 4th. That would probably make the trans happier.

See what happens once I get to test it out this weekend.

 

[Greg Ducato]

10-4

 

[KirsL]

Finally got to out her back together. I took some laps around the neighborhood to warm up the trans some to get the right amount of fluid in. Took her for a quick ride, hit 55. Not sure if I didn't cruise at that speed long enough but no tcc lockup. Going to try and go for a longer ride tomorrow and see if it stills doesn't work.

So looking more and more like I'll have to change the torque converter. So though I know a complete overhaul is better. Is it worth trying just changing the tc since my budget is super limited. Or should I just start to budget to do a basic rebuild myself?

 

[Greg Ducato]

I think you should remove and test the TCC solenoid first to be sure it is holding pressure when activated and using a scribe stroke the TCC valve in the pump to be sure it isn't sticking.

 

[Blue85]

The TCC can be tested. Call around to see who will do it for you. Obviously try all the other troubleshooting first, but if you get to the point of pulling the tranny, that quick test will let you know for sure before you buy a new TC and/or before you re-install the trans.

I've had a couple bad ones over the years. One wouldn't hold pressure and the other seemed to just have no friction material left.

 

[KirsL]

I think you should remove and test the TCC solenoid first to be sure it is holding pressure when activated and using a scribe stroke the TCC valve in the pump to be sure it isn't sticking.

Other then being installed how would I test the solenoid? I feel and hear it click when it's powered up.

So using a thin punch I should be able to move the valve that's above the tcc solenoid?

If it has to come out I definitely have it checked before reinstalling it. I'll have to see who in the area can do it.

 

[Greg Ducato]

Other then being installed how would I test the solenoid? I feel and hear it click when it's powered up.

So using a thin punch I should be able to move the valve that's above the tcc solenoid?

If it has to come out I definitely have it checked before reinstalling it. I'll have to see who in the area can do it.

When you pull the solenoid you can use a rubber tipped air nozzle to shoot air into the snout, there should be little to no leak when energized with 12V, you should be able to stroke the TCC valve through the little hole in the retainer which is visible when the solenoid is removed.

 

[KirsL]

When you pull the solenoid you can use a rubber tipped air nozzle to shoot air into the snout, there should be little to no leak when energized with 12V, you should be able to stroke the TCC valve through the little hole in the retainer which is visible when the solenoid is removed.

Got it. Off to see what I find out.

 

[Blue85]

There's an old trick to put a check ball in the solenoid to make it like the solenoid is always "on". It's to separate electrical issues from hydraulic or mechanical ones. (I understand some people actually drive around like this full-time though ). Greg can comment whether this is a good idea.

 

[Greg Ducato]

I wouldn't leave it like that because it kills torque multiplication in the lower gears but it can be used for the purpose of testing, lockup will come on just after the trans shifts to second gear if modified in this way.

 

[KirsL]

There's an old trick to put a check ball in the solenoid to make it like the solenoid is always "on". It's to separate electrical issues from hydraulic or mechanical ones. (I understand some people actually drive around like this full-time though ). Greg can comment whether this is a good idea.

I don't have any extra check balls with which to try this plus I don't think it would be a good idea.

I got her drained and started to pull the pan but got a call back to go for a job interview. So truck waits till tomorrow. Feel pretty good about the job . Now just to wait for the weld test to come back.

 

[KirsL]

So finally got to testing the solenoid and the tcc valve. The solenoid allows air to pass when not powered. Blocks the air when powered. The tcc valve moves freely when pushed. So I'm pretty sure the convertor clutch is toast. Sotime to save for a new one.

On a positive note that will be easier since I heard I got a new job that I start on Monday .

I'm thinking I want to keep what I spend on this trans low. Long as it works for the time being I'm happy. I say this because I've been debating if I want to swap the 700 out for either a 4l80 or a nv4500 or just stick a built 700 in. So being usable when needed is all that matters for now.

 

[Greg Ducato]

Congrats on the job!! Be sure that your converter supplier knows that they are building a diesel converter with the appropriate stall speed and damper design, you will also need to know if your input shaft has 27 or 30 splines and if the converter cover uses three or 6 mounting pads.

 

[KirsL]

Thanks, should be a good fit at this place. I'm happy to be back to work.

Current converter uses 3 mounting bolts. Not sure if it helps any but found this numbers on the pan rail, 3T829 2D. I'll have to pull it eventually to make sure.

 

[KirsL]

Finally had a chance to pull the trans to confirm which spline count the input has. Both set of spline are 27 count.

I think I might need to pull the t-case apart though as the fluid was more strawberry milkshake then bright red. Shouldn't be too bad to rebuild it. T-cases are pretty simple. Course I'm wondering if I should do the same to the trans, just a basic going through. Just not sure if I should or not.