V6 To V8 Done Wrong?.. Tranny Shifting Weird

karlosg23 · March 11, 2011

Hi i just bought a 2003 crewcab. it had a v6 but the previous owner swaped a 5.3 on it. the engine is good but the tranny is shifting off and randomly changes. any ideas whats wrong?might it be they didnt switch the computers or do i need a custom tune?..thanks for taking yall time.

Stevens03 · March 11, 2011

Was the transmission swapped and what PCM was used?

Also what Year motor?

karlosg23 · March 11, 2011

Was the transmission swapped and what PCM was used?

Also what Year motor?

he got a 05 5.3 whit 38k miles. they only shitched the bell housing on the tranny and idont know what pcm means.

beave84 · March 11, 2011

Was the transmission swapped and what PCM was used?

Also what Year motor?

he got a 05 5.3 whit 38k miles. they only shitched the bell housing on the tranny and idont know what pcm means.

Powertrain control module.... computer

Stevens03 · March 11, 2011

Most likely the wires going to the transmission aren't plugged in right or pinched. The transmissions would be the same or similar enough between the 4.3L and the 5.3L . You still may need a tune for the transmission. Email Blackbear performance and ask Justin if you'd need a programming update for the 5.3L

I'd imagine the all the shift points and shift pressures would be different for the two motors.

nickvrebel · April 2, 2011

I didn't know that they made a Crew Cab with a V6?

What's the VIN? (Is the 8th character a "X"?)

Transmission:

To swap a 5.3 in the place of a 4.3 is quite complex. I've seen it done twice, but there is a lot involved.

The transmission is slightly different. The bell housing and the input shaft/ pump/ torque converter are different. There is a conversion converter that exists but it's use isn't too common.

Tuning:

it wouldn't run on a V6 tune, it's completely different. The tune would need to be checked and would be the culprit unless it has a Vacuum modulator added to the transmission (uncommon, not factory, well, was factory back before computer controlled transmissions but is an old school trick to use on modern performance transmissions).