Converter lock up too soon?

[jasonconaway]

I recently repalces some rotten vacume lines, and caped some that I wasnt sure where they went on my 84 c10 305 auto trans. . I know the one for the converter lockup is connected, but since I changed all the lines, when it shifts from second to third it is normal for about one second then its like it hits another gear and bogs the engine down a bit till I build up more speed. This is while accelerating easy. Seems fine when I get on it. There wasnt a big change in engine rpm when changing to 3rd before I replaced all the lines. What could be causing this bog? Is it locking up to early?
Thanks!

[Gmc-76]

I just started randomly having what sounds to be the same exact problem today, any feedback would be appreciated from me to!!

[50seven]

As I remember the 700's don't lock up in first. They lockup in 2,3 & 4 unless they are told not too by the TV cable, manifold pressure switch or the break pedal switch.

I bypassed the vacuum switch because I was running a cam and the pressure switch wasn't right. Never had any issues other than not liking the 700r4's.

Check the TV cable is adjusted properly? Check The vacuum lines are not causing a massive leak somewhere? Put a temporary tach in for diagnosis should drop 200 rpm upon lockup and vice versa? Check the switch on the brake pedal it has adjustment in it also. But most of these faults would cause a non lockup issue.

I would have look at the vacuum switch first (did you take the wiring of this switch out of the equation or just cap off the vacuum lines)? They electrical portion is probably still trying to control lockup.

[vwzkc]

I have the exact same problem, somebody told me it might be the governor in the trans. Idk. Curious to see some more responses though.

[cadillac_al]

Did they ever work right in '84? My Dad bought a new GMC C15 in '84 and that thing never knew what gear to be in; even when it was new. We just lived with it for 5 years until he bought an '89. It probably is TV cable related but we weren't hip to that back then.

[vwzkc]

Did anyone find out anything else on this subject?

[beamn7]

Seems almost all of these used to lock in 2nd or 3rd depending on engine load / how heavy your right foot is at the time. Can be very annoying as well as wear on the converter clutch and thrust bearing / crank after years of it....
I wired up a relay and a 4th gear pressure switch to allow for lockup only in 4th. Easy to do or you can buy a kit for this also. Many aftermarket kits available via summit, etc...

[vwzkc]

Did anyone solve this? Would be nice if someone did to post a follow up.

[jhngardner367]

It may not have the 700r4 trans.
Does the shift indicator have a "D",with a circle around it,and another "D",then 2,then 1? If not it is probably(as in my '85) a 350c trans.
These trans.,have a vacuum-actuated switch,usually located (looking from front of truck) in the upper left cowl area. It closes the solenoid,in the trans,to lock up the converter clutch to provide a direct fluid coupling( 1 to 1 drive).
When the brake is used,during stopping/slowing,it disconnects the solenoid,to allow the vehicle to idle without stalling.
Mine locks in at about 35mph.
The "bog" you feel,is the converter locking in,and is normal.

[vwzkc]

im pretty sure we are talking about a 350c trans and there would be no overdrive only d21 on the selector. not a 700. ive tried unplugging the connector on the trans and adjusting the kickdown cable, and checking the vaccum modulator and still same problem. im convinced its the governor in the trans. thats my next step unfortunately. i will post anything i find out.

[gchemist]

Swap the govenor for a Vette one. Shifts will definately change. Connect a hand vacuum to the modulator line. Check for vacuum loss.