JKM

I have been having MPG issues on this truck since i got it

Click

I knew the tranny didn't feel right, yesterday when i pulled onto the highway , i counted the shifts , second , third , o/d , then all the sudden, WHOOM! rpms dropped instantly and i felt like i was riding a rocketship, the TQ had locked up.
I knew this tranny didn't shift into o/d like it should. I lost lockup when i let off the pedal just down the road , and only saw it lockup once more much later that day.

So , now , how do i troubleshoot this to find the cause? I'm going to have the tranny pan off this weekend to change the fluid and filter , how can i test the solonoids to ensure they both work while i am in there? (and is there a pan gasket , or it is just RTV?)

Last weekend i lost o/d completely , but i got it back by cleaning the TPS (drilled hole and squirted in cleaner) I have not yet adjusted it , but i am going to do that this weekend also.

Is there anything else i can check/do?

mr T

just set urself up a tc lockup switch for now so u can lock up on the highway in OD at least...i think ur tps could always be toast too..i tried fiddling with mine for aweek before i simply just bought a new one...thats a hard one to swallow cause the tps is pricey

JKM

I know i can just wire a lockup switch , but why would i bother with the hassel when i can just fix it right. I want to know how i can troubleshoot this, where on the transmission is the connector with the wires for the 2 solonoids? Is it the round one with 3 wires going in on the driver side , pretty high up on the housing?

Mr. Jimmy

Wiring the lockup switch will allow you to know whether or not it is the solenoid. I just went thru this on my 95, turns out it was the TCC solenoid. I bought a TPS from Oreilly's and tried that first, took it back for refund once I was sure that wasn't the problem. The solenoid was $41 from Trans parts but you will probably pay a lot more if you go thru the dealer or parts store.You may want to call Dave at Goerend trans and talk to him, he is very helpful.

JKM

I guess i could hook up a temporary switch to test it , what wire do i need to tap into for this?

wiring diagram anyone?

Mr. Jimmy

Check for 12 volts at center pin, if you have this, then will driving ground orange black wire and convertor should lock above 55 mph in OD.Another possibility is your brake switch underneath dash.

JKM

You completely lost me here dude?

Where is this center pin? If i do , what do i do with it?

Mr. Jimmy

It is a 3 wire connector located on the driver side of trans, above the pan. You should have 2 wire harnesses on this side.A neutral safety switch and the OD/TCC lock harness. The neutral switch goes into the housing at an angle and the TCC solenoid mounts straight down from the top above trans pan.Check center pin of the TCC harness with a volt meter with key in on position, engine not running, ground the - side of meter somewhere and you should get 12 volts. After this is done you can take a scotch lock connector and splice into the orange/black wire and run into the cab of truck thru door or window. Now go for a ride with the trans warmed up, get to over 50 mph and have someone ground this wire onto something in cab and see if convertor locks.As I understand it this will also rule out the TPS being bad. Replacing the solenoid pack isn't that bad if you are mechanically inclined, just watch out for the park detent ball to jump out and it is fun getting it back into position so I would be certain that it is the solenoid pack before digging in. Good luck.

JKM

That was alot clearer , i think i might try that this weekend. Thanks!

JKM

Update , i did as Mr. Jimmy suggested , ran a wire from the orange/black wire into the cab , and tried grounding it once over 55 in o/d , and absolutly nothing happens , i'm going to check my connection tomorrow morning , and make sure it didn't come loose or something.

The weirdest part is twice today right after i got on the freeway it locked up as soon as i hit 55 , and stayed locked until i let off , at which point it unlocked.

I'm going to have the pan off tomorrow to change the fluid and filter , and i want to test the solonoid (s) while i am in there , anyone know what the OHM rating is supposed to be? Anything special i should know to test them?

Mr. Jimmy

Did you check the brake light switch ? Try pulling up on the pedal while driving over 55 and see if it will lock. The switch can still be bad even if the brake lights are working, switch is about $7 at Auto Zone. You may also want to hook a volt meter up to the center pin on the connector at trans at wiggle it around to be sure you are getting a constant 12V. If you are going to drop the pan and are confident that you can change the solenoid pack, I would go ahead and replace since you are already half the way there. If you can't find a reasonable price on the solenoid let me know and I will give you the phone number of the parts house that I bought mine from for $41. I have heard of people paying $125-$200 for these.

JKM

I'm dropping the pan today, So if i change solonoids , it won't be today.

I may try throwing a brake switch in it sometime this week, if they are indeed that cheap.

I'm going to test the resistance in both solonoids , because i don't know what it is supposed to be , and i figure they should be about the same...

Where are the solonoids themselves located? I think i should be able to switch them out myself , i am a mechanic by trade...

Mr. Jimmy

The solenoids are located on driver side of valve body. You will have to drop the VB to get at the bolts that hold the pack on.This is not a tough job , just watch for the park detent ball to shoot out of it's position in the VB as it is spring loaded and can be fun getting back into position without the special vise made for this,but can be done with a small screwdriver and someone assisting you.

turbo thom

One thing on 94 I bought, was the tps was broken. If you take it off you will see the rotating contacts are controlled by a spring. My spring was broken and completly in operative. That was replaced and then I installed a switch for lockup and one for overdrive. My lockup is controlled by the switch totally, I cut the wire, and overdrive is in conjunction with the OEM operation. I spliced into the OD wire. I have lights, one green and one red, to work with each switch. Works well, and I like the control I have over both operations.

..Preston..

JKM

My tps is fine , i have narrowed it down as far as the solonoid or wiring in the tranny being bad , from the contacts on the top of the tranny, there is an open somewhere in the system. the one for o/d tested fine though.