Trans slipping in and out of OD

[1984 t-type]

After cruising around the city for about 100 miles on the freshly rebuilt motor I to put her on the highway and open her up. When I'm cruising at highway speeds it feels like the trans is going in and out of overdrive, what could be the cause of this ? P.O. Said that the trans is rebuilt and has a 10" 3200 stall I think got I wrote down somewhere if that matters. Please help I'm scared to drive her now, I don't want to ruin the trans especially if it's a simple fix. Thanks in advance

 

[IrvJr]

Are you sure it isnt locking/unlocking the converter? First thing i would do is drive it around in 4th and use the top of your foot to pull the brake pedal back. That will determine if the brake switch is just out of adjustment. If it is then the converter would stay locked. If its just 300-400 rpm its the converter, if its more like 700-800 then its going to 3rd.

 

[1984 t-type]

If it is the converter locking and unlocking why is it doing that, and how do I fix it. Seems like it's only a couple hundred rpm's that it goes up when it happens, if it is going from 4 to 3 what would that mean. Headers are off now waiting for Mark to send me new gaskets so I prob won't get it back on the road till this weekend but I just want to know what all to chech for. Could the tv cable have anything to do with it

 

[TurboDave]

If it's only a couple hundred rpms then that's likely the converter kicking in and out of lock

 

[1984 t-type]

So why is it slipping in and out ? And is this normal ?

 

[SSedan64]

Not normal. Could be TPS, Brake Light switch, TCC Solenoid or ECM causing the problem.

 

[IrvJr]

First and easiest test to do is check the brake switch. Thats done by doing the brake pedal test like i mentioned before.

 

[JUSTA3.8V6]

u could manually shift it into D when u think it slipped out of OD. if the REVs dont change then its in third and its not the converter.