TreDeClaw

I dropped a 350 with carb (350-400 hp crank) instead of my cfi 305 in about 100-150 miles ago and now my car is having trouble, or just wont shift into 3rd gear. It will catch for a second or two once the rpm's go up.
The old trans oil was clean, not burned and we did filter and oil change on the trans and it is still slipping.
1 - 2 shift is good and strong and drives fine if not fantastic in those gears and I can drive it with the manual shift in 2.
I went to a shop and he suggested to change the ecm or pcu whatever or both because there might be some wires going from the trans to the computer which is obviously not connected anymore because the original injection system is off.
could the TV cable have been not adjusted correctly? We did exactly how it should be done. Button, push in, release button, full throttle. And wouldn't all gears be affected?

Trans and torque converter is stock to my understanding.

I am just not finding any research backing up the claim of some ecm or pcu having an effect on the transmission, and he is just trying to help me before i spend X amount of hundreds of dollars trying to see what the issue is.

Also, some research on a torque converter lockup (or something like that)? I am interested in what that is.

Thanks for any help!

willexoIX

#1. What was the original motor before you swapped?

If it was different than the one you swapped in, you may need a TV cable relocation bracket for correct TV valve operation. If your TV cable is not "set" properly, it can burn the trans in a very short amount of time. Though you said you adjusted, or as the correct term is "set", the TV cable correctly, if the TV cable geometry is off, then the TV cable was not "set" correctly to begin with.

Pretty sure I got all that right, anyone correct me if im wrong

paulo57509

If it was shifting fine 100-150 miles ago and now it's slipping when shifting to 3rd, the 3-4 clutch pack is already fried.

You won't necessarily have obvious burnt fluid when this happens. I have an '03 4L60E that fried the 3-4 clutches and the fluid wasn't burnt. Just a slightly darker red color.

You can continue to drive it in manual 2nd without further damage.

Shifting of the 700R4 isn't controlled by the ECM so forget that theory.

IIRC, the torque converter will lockup in 2nd, 3rd and 4th. In case you're wondering, torque converter lockup isn't the cause of your slipping 3rd gear.

willexoIX

I hate to argue, and dont take this the wrong way, but if improper TV cable geometry is the cause it will cause more damage if not fixed, though it sounds like it already needs a rebuild. If the line pressures arent right it will definitively cause more damage regardless.

Even if its set properly, if it needs a geometry correction kit then its not set properly. Though I dont know much about transmissions, I have done all the reading I can on the TV cable and 700R4 cause my car has a 280,000 mile 700R4 in it with no rebuild. There should be no reason that the clutch pack would burn out within 150 miles, unless there is something seriously wrong, and it sounds like the TV cable TBH. But what do I know, im not a trans guy.

paulo57509

No, you're not argumentative.

But no where in my post did I mention any kind of root cause for the slipping 3rd gear. It very well could be a non-stock application causing TV cable geometry issues. Also, the 3-4 clutches are prone to failure in these transmissions even when the TV cable is properly adjusted.

All I'm saying is that the OP's description of the 2-3 shift as being "slip-grab" is exactly how the 3-4 clutch starts to fail. A throttle geometry corrector might fix it but once it starts doing the "slip-grab" thing the damage is already done.

My personal experience with "slip-grab" 2-3 shifts is that it took less than 65 miles (in heavy traffic) on the interstate for the 3-4 clutch in my '03 M-Body 4L60E to stop holding completely.