TCC (Lock up) not locking up on 91 burb 700r4, where to start?

[eagle mark]

Pin D7 on ECM, Tan wire Black stripe.

 

[GonicGM]

The TCC lock up changed over the years as to how many wires were used and where they went inside the trans. IIRC my 700R4 is a 1 wire system.

If I'm not mistaken, all TH350C had two position plug, both populated. all TH700R4 had 4 position plug. My 1983 8600 GVW K2500 has factory TH700R4, no ECM. This was only done from 1982-1984 on C6P chassis trucks. Only two positions are used on the 4 position plug.

IIRC, most if not all ECM controlled TH700R4 used 3 or 4 positions of the 4 position plug.

 

[GonicGM]

In the mid-80's there were two devices on the K/V trucks that interupted the lockup outside of all other controls, the brake switch, as mentioned before, and the 4wd relay. If 4wd is engaged, the relay opens/breaks the power to the lockup converter solenoid. I'm uncertain if this relay is used up through 1991.

 

[pma4x4]

well either way the problem is in the tranny. Like I said, I did the temporary manual TCC lock up test by toggling the A and F pin on the ALDL. I get a 12v signal at the plug but the tranny is not doing anything.

 

[GonicGM]

Pin D7 on ECM, Tan wire Black stripe.

This diagram is rather over simplified. As the diagram is labeled solenoid, it is representing a lot more. Please note that within the diagram of the solenoid is in fact a solenoid but also two switches. The diagram is actually representing three entirely different things but certainly related. The solenoid as a device, a wiring harness and two or more valve body mounted switches. The switches and wiring harness are most certainly external to the solenoid. Two switches that typically exist on the valve body are one for 4th gear and another for 4th to 3rd downshift. On non-ECM controlled TH700R4, the 4th gear switch is a two terminal series normally open switch. On ECM-controlled, 4th gear switch is typically a ground switch, grounded with pressure. When someone installed the trans. in my 83 K2500, the internal switches and harness installed were of the ECM controlled type. Where mine was supposed to have a normally open two terminal inline switch on 4th gear pressure to provide 12v to the solenoid, I infact had a single wire ground terminal. Result, everytime the vehicle shifted into 4th gear, it would blow the fuse. Obviously no lockup took place. Ironically, the torque converter solenoid shared the same fuse as the radio on a C6P 1983 K2500. Until I reviewed the diagram and rectified the situation, I would blow the replaced fuse on the same section of road on the way to work every day and the radio went out. Point is, you could have a good solenoid and a bad or incorrect harness in the transmission, or a bad valve body switch or an incorrect swith installed on the wrong tap. Forgive me for possibly complicating the possibility but realize all the possibilities from someone who has been there. The ECM just complicates the more simple control of a vacuum switch, temperature switch, brake switch and 4wd relay that controls mine, external to the trans case. Good Luck!

 

[pma4x4]

I understand where you are coming from. I have checked all external sources that control the TCC. Everything checks out. Something is not working in the transmission. Like i state in on of my earlier posts, the transmission is or at least should be under warranty since it was done in May this year and has less then 3000 miles on it. I say may becuase they mey tell me to shove off since I am not the original customer.

I am planning for them to send me packing so I am researching rebuild kits, TCs, Solenoids and shift kits.

 

[pma4x4]

Updates. Tranny shop is saying internal wire harness is bad. they are warranting it and the new harness should be here tomorrow.

Tuesday at 3

shop: was a bad wire harness
me internal or external?
shop: we think its the internal but could be external they were known for going bad
me: I test the harness and the tranny gets a TCC signal at the connecter
shop: We are warranting the harness
me: when you rebuilt this tranny did you install new solenoids?
shop: yes, we do on all rebuilds. call tomorrow around same time

Wednesday 1:30
Shop: they are working on it right now. call me around 4
me: ok

Wednesday 4pm
Shop: the harness we got was not working so we are over-nighting a new harness from CA. Call tomorrow afternoon and speak with ***.

 

[pma4x4]

Harness is good, they are replacing the solenoid tomorrow. I guess they dont replace them on All rebuilds. "Harness" crap its like 3 hi-temp insulated wires and a connector.

They are going to go thru all the external testing to see if its the brake switch and yada yada. I told them the harness gets a 12v signal at the connector so its somewhere in the tranny. There was a slight pause after i said that. "ok well we are going to check the switch and swap out solenoid anyways." I told him the EBCM showed possible bad but that I could not confirm if the ABS module is tied into the TCC or not, he didnt know on that one either.

This is the 3rd time in my life having to deal with a tranny shop and all I ever hear is guessing and parts swapping till it works. I swear trany shops are just magic and voodoo specialist who do things till it works and makes it look like they knew what they were doing.

I told them I got it hot driving it home and could smell warm ATF, but no its all right, here have some pixy dust and candy.

Rant off. sorry, just frustrating.

 

[dyeager535]

This is the 3rd time in my life having to deal with a tranny shop and all I ever hear is guessing and parts swapping till it works. I swear trany shops are just magic and voodoo specialist who do things till it works and makes it look like they knew what they were doing.

Pretty certain TCC isn't tied into ABS, there is no reason for that, the brake switch would unlock it no matter what. No brake, no ABS.

I think you can probably change tranny shop to "mechanics in general". I won't badmouth all of them, but I've certainly seen my fair share of shops do shoddy work, let alone what has happened to others. If the computer gives them a code, they replace the piece. If that doesn't work, they replace another piece, guessing with your money until they get it right.

At least in your case they aren't charging you for their incompetence!

 

[pma4x4]

They are out on a test drive at this moment so we will see. I guess in order to get to a test drive point the solenoid must have been clicking then.

Update: they got back and still no lock up. they are pulling the converter and putting a new one in on monday.

 

[4X4HIGH]

I have a friend who owns a trans shop and has been in business for over 40 years and he KNOWS what he's doing and has built every trans i've ever needed built and never a single issue. He built my 700R4 about 10 years ago now and it's still running strong.

 

[pma4x4]

I had a friend that went to school on it and ended up opening his own shop. He was doing good last I heard.

I think part of it is just behind how "mysterious" the automatic tranny works and its complicated design. Brakes are simple to fix, there are only a couple of components that are needed to make a car stop and they are all large items to work with comparatively.

They said that had the converter in stock so maybe Monday. I am still glad they are honoring their warranty with me. Plus they tell me to call them each day for progress.

 

[pma4x4]

Got a call from the tranny shop today... "come pick it up".

I got there and this was the final results

1 new internal harness
1 new Solenoid
1 new Torque Converter
fresh fluid, new filter
and a free tranny mount to boot.

Totoal cost $000.00

Basicly the TC crapped out so hard that it fried the solenoid and also was making shifting feel... "odd".

had a nice firm lock up in 3rd cruising the streets and a nice firm lock up in OD on the highway. Tap the brakes it pops outs.

I am guessing it may have crapped out before I bought it. because when i got it, there was a slight rpm related faint ticking sound coming from the tranny hump. The same sound as baseball cards in spokes just very faint. THAT SOUND is now GONE.

I went for the test drive noticing it had more defined and firmer shifts i got back and asked them what all they do to these things on a rebuild. and my guess was right. they put a mild RV/towing shift kit in it. He said I can put one in myself it wont void warranty. He also noted the good work on a proper tranny cooler.


These guys turned out great, it was just my paranoia.

Happy trails and off to California with it.

 

[Greg Ducato]

Glad it worked out for you and Kudos to the shop for taking good care of the issue and customer.

 

[pma4x4]

Truck and tranny survived the 1400 miles from Phoenix, az to Gorman, CA to Death Valley to Las Vegas, NV and back. stop and go cold and warm weather. 8% up hill and down hills. low gear and cruising. lock up worked as should!

EPIC WIN!

 

[dyeager535]

Great to have something you can trust, isn't it? Congrats!

 

[eagle mark]

Sounds like a fun trip.

What kind of mile per gallon did you get?

 

[pma4x4]

Math came out to 13.05 mpg

Flatland cruising we were seeing 15.02, worst was like 12 something. total altitude from 8500ft in the Sierra Nevadas to -240ft in Death Valley. With some really gnarly steep grades down to 2nd gear stuff. Actually heading to one of the trailheads for Mt. Whitney was 1st gear on the Whitney Portal Rd.

Still better MPG then our loaded Jeep Cherokee was and more room to boot!

 

[warrior9]

dude, youre not paranoid about tranny shops. I have had my ins and outs with several of them around my house. Tranny work is the only thing I dont do myself and its frustrating when youre dealing with a bad shop. Glad it worked out well for you. You got a nice truck. Glad youre enjoying it.

 

[nutt7]

What's the name of the shop? I live in the valley and would love to check them out if needed...

BTW, I did that same climb out of Death Valley to Lone Pine...in 125 degree July! My burb hated it...especially with the Ultramarathoners on the road. I have since upgraded my tranny cooler and radiator and fans largely because of that misery...we had to kill the A/C and take breaks every 20 minutes or so to let it all cool off!

My sig pic is on the way into Death Valley, and avatar pic is in Alabama Hills with the Sierras in the background.