Strange OBS auto tranny prob.

JoeDaddy

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My 96 2wd auto is disengaging at idle. It works great as long as you stay in the throttle even a small amount. The minute you let off for a hill or stop it slips onto N and will only engage with some throttle. Doesn't slip at all just won't stay engaged.

I changed fluid and filter and no help.
 

Pstroke96

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could be the pump, we had a chevy at work do the same thing, when you put it in gear does it engage like it should or does it take a few seconds?
 

Mark Kovalsky

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I think you need to put a pressure gauge on the test port and see what line pressure is doing. The gauge needs to be a 0-350PSI gauge.
 

JoeDaddy

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That's solid thinking, its got to be losing psi.
I had a few minutes to jack with it this morning. Start and put in D and it engages immediately. I went from D R N several times while letting the engine warm then took it for a ride in the field. Romped it a couple times and it stayed engaged the whole time. I then took it out on the pavement and rode at 75 for a few miles turned and came back. With it parked and idling I rechecked the fluidd level and then did the prndl shuffel again. About the 3rd time into D it hesitated and lost it completely on the 5th time. It would reengage if I put it in 1 but then that went away to.

I forgot to mention b4 that when it 1st started acting up it would find D after sitting off for an hr or so.

Im going to pull the lines and do a loop when I get a chance, I'm wondering if there might be a bottleneck in the cooling system.
 
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JoeDaddy

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That's true, there's not 2 gallons of dead space in the cooler I suppose :doh:

So that leaves pump or VB. Will the pump lose psi as it warms? Cuz It's working great until it warms up, and even warm letting it sit for a bit causes it to work again. Loose or warped VB ????
 

JoeDaddy

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After Marks thoughts and another trans man's, the front seal sounded most likely to be the culprit. Knowing this would result in a teardown I thought why not try some snake oil? nothing to lose right? So I went with a bottle of Lucas.

Now understand that I had 0 expectations from this, it was literally a shot in the dark as far as I was concerned... and 0 is what I got. Did as the bottle directed and nothing. After letting the truck sit and buying another I'd come to the conclusion that I'd pull the engine and throw it in the 1/2 ton.

Monday morning I decided is drive the ole girl to work 1 last time b4 putting it under the knife. Got 1/2 way to work and got stopped waiting for a pilot car in some road construction. I heard the rpms come up as D disengaged and I prayed that it would go back in, which did with some throttle. Got to work, then returned home w/o issue, the tried R D shuffling and lost D on the 2nd time as I recall.

Thinking I'd rather drive the last gallons out than siphon them I tossed fate and drove again tuesday, no probs. Returned home in the afternoon and did the R D shuffle again but this time it didn't let go! Mystified I shut it down and decided to do some work on the 1/2 in prep for the impending swap. That included dragging the cab-less chassis to the car wash for pre-paint cleaning. I decided to use a tow-bar and hitch it to the hurt truck. Having no steering wheel and no weight from the bed forward the short trip required many un-planned back-ups to keep the front tires from cocking sidways. It NEVER lost D! Not b4 or on the return. After unhooking I repeated the DR thing many times b4 giving up and going inside.

Needless to say I drove it again this morning and its right as rain. WTF! Am I stupid or Justified for doubting the Lucas? I have about 5 tons of scrap to haul next week on a 4000 lb GN. its going to get a shakedown at 20k gross to prove itself. If it passes initial testing it will get refueled and make the 70 mile 1-way trip at the usual 70mph ac cranked cruise set trip to show me.

I'm not trying to kill it but sucess means different things to each, and this truck has never nor will it ever be babied. If it survives Lucas will be getting a letter and a link to this thread, hell I'll send them a video of it pulling its guts out if it passes!

Fingers crossed.
 

Mark Kovalsky

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It means that most likely the forward clutch seals are worn out. The stuff you put in swelled the seals so that they will work again for a while.
 

JoeDaddy

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It means that most likely the forward clutch seals are worn out. The stuff you put in swelled the seals so that they will work again for a while.

If it gives me time to plan for the eventual breakdown then its a win. I'm considering rebuilding myself since I'd like to drop a 4wd output shaft in 1st, where's a good source for the clutches, steels and TC? Is there a good link to an exploded view of the e4od to bone-up on the tech?
 

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