V6 To V8 Done Wrong?.. Tranny Shifting Weird

[karlosg23]

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]

Was the transmission swapped and what PCM was used?

 

Also what Year motor?

[karlosg23]

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]

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]

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]

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).