Hello all,
I'm new to the forum. I have a 1967 Chevrolet Belair with a 5.3 and 4l60e combo out of a 2003 Silverado. This car has been my daily driver for 3 years since completing the swap. Recently the trans has decided that it doesn't want to go into 3rd or 4th. At first I thought the 3/4 clutches were bad so I was shopping around for a rebuild. But when I was headed home I decided to try to shift manually and as long as I don't go to 3rd before about 40 mph(around where the TC locks up) the car will shift to 3rd then 4th like normal with the TC locking like it should. I have been driving it like this for 3 weeks. Just wondering if anyone has heard of this before.
Thanks,

 

The very first three things that you should do, are:

-Inspect for proper ATF level with the unit warmed-up, in park, and with the engine running.
-Inspect line pressure in all the gear ranges; both at idle and above idle.
-Inspect for any type of diagnostic trouble codes from your Power-Train Control Module.

Is the Transmission completely stock?
If not please state any modifications.

There is a somewhat large amount of fluid needed to make the shift into third gear, and another small amount to shift fourth gear.
Check the things I mentioned first and then get back to us.

Also, has the transmission ever shifted: 1 to 2 to 4, skipping third gear if second gear is rev'd-out?

 

The fluid is full,
i don't have a way to check line pressure currently.
The trans is stock and I don't have any codes.
​​​​​​I forgot to mention in the first post that this problem started about a week after I changed the fluid and filter, so I'm not sure if that has something to do with it. Also if I shift to 3rd too soon and it "slips" I have to pull it back to 2nd or 1st, stop, then take off again. It's like once it slips It won't go to 3rd no matter how fast Im going when I shift until I stop or slow way down (15ish mph).
thanks

 

You really need to rent/ buy a line pressure gauge.
You also can try to over fill it a quart at a time, up to 2 quarts... as the dip-stick measurements are often wrong.
See if that restores 3rd and 4th gear.

Next, unplug the electrical connector from the case, and start the vehicle and try to drive as normal with the gear selector in over-drive.
The transmission should act as if it is in 3rd gear only.

Please report back.

 

I pulled the main round plug on the passenger side. I have reverse. I pulled into od, it started and stayed in first. Then I started pulling it down, when I went to 3rd, it stayed in first, when I went to 2nd it shifted hard into 2nd. Pulled it into first it will go back into 1st at a low speed or coming to a stop. When I shifted back up I got into 3rd and it stayed there until I pulled the shifter back down to 2nd or 1st. I bought a pressure tester, and will try that next.