Engine revs while driving... HELP

[Ardee83]

Ok I will do my best to give as much detail as possible.......

Setup 83' SWB 2wd brand new 350 (800 miles) with a rebuilt 700r4 with 23k miles on the rebuild and was told it had a shift kit.

About 2 weeks ago I noticed that when I am driving in OD, 4th gear around 60mph and just keeping it steady at 60mph and 2k rpm the engine will rev and the tach will jump from 2k to 2300 to 2400 and the truck springs forward, then settles back to 2k.

So I did a test and drove the truck at 60mph in Drive, 3rd gear. No revving, so I slowed down so I was running 2k again no rev shifted back up to OD. The revving issue started again.

When I got home I checked tranny fluid, it's perfect. Checked the plugs and the wires, looks perfect.

I did record the tach jumping so others can see what it's doing, sorry I was driving and its not hollywood quality, but you can see about half way through the video it starts jumping. http://youtu.be/jT1XqpVR80I

I am not sure how to proceed from here...............
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[geezer#99]

LOck up torque convertor does that! It's controlled electronically thru a switch that senses vacuum in your motor. A slight touch of the pedal drops the vacuum, kicks out of lock up. Your motor slows down, vac goes up, it locks up again.
I bet you've got a higher speed rear gear in there.What's your rearend gear ratio?

[Ardee83]

I do not know my rearend ratio. I do know its the standard. My build sheet shows its a GQ1. Locking Torque Convertor, why wouldn't it do it in all gears vs just OD and only at a certain rpm/speed?

[geezer#99]

Cause it's controlled electronically inside the tranny. Has to be in 4th for the signal to the switch to work.
Did you have a turbo 350 in it originally?

[Ardee83]

Ok I understand now. No it came stock with the 700r4 and the same 700r4 was rebuilt. Since this is something that just started could it be the sensor that is faulty?
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[geezer#99]

Maybe not. Might be in your motor. I see you mention a new 350. How was it built? Stock or more performance?

[Ardee83]

Yes it's a new 350 GM Crate motor it's stock. I added an edelbrock intake and hooker headers. All internal parts are stock. The carp and rotor are new and all the sensors on the motor are new as well as the plugs wires pulleys belts hoses and motor mounts
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[geezer#99]

Your new motor with the headers, intake is more efficient at a higher rpm than your stock motor was. THe new motor likely likes a 2500 rpm cruise. Your stock motor was happy at 2000 rpm. You've moved the torque curve on the motor up the rpm scale. Your new motor makes less torque at 2000 than the old one. The new motor won't run nicely at a lower rpm so it starts to lug a bit, vacuum drops, the sensor picks up on that and it kicks out of lock up.
It's the nature of the beast.
I bet it won't shift in and out at a higher speed.
Some people splice a switch into the power to the lockup so it won't lock up till a higher cruise rpm. THe constant in/out is annoying. Mine does that around town. I manually shift it back a gear till I'm up to a little more speed.

[Ardee83]

Ok. but what I am not understanding is that this issue just began after 800 miles of driving. If its because of the new motor wouldnt it have begun doing it right away?

[Ardee83]

Bump. Looking for some other input and opinions
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[Ardee83]

Sorry I'm murdering this thread. If it is in fact the sensor I should be able to disconnect it and it shouldn't go in and out, right?
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[INSIDIOUS '86]

If you disconnect it it causes to much heat build up from not locking up. This can/will kill the trans.

What carb do you have? Do you have the adapter for the cable on aftermarket carbs? How us your t.v cable adjusted? Should be able to have the throttle at full and the cable unable to go past full throttle, this Is max setting

When it cycles in and out how far is your foot on the gas? Stock 700r4 like to kickdown early. Check any of the vacuum switch hoses for a leak as well
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