47rh won't go into OD
 

I have a possible vacuum leak, I notice it in my brakes not assisting if the engine is idling and I use them a few times. Would that cause it?

What other possible culprits should I check?

opps sorry I got this in the wrong forum section

Your title doesn't match your post? A weak pump or bad hoses will cause a low vacuum issue. Have you recently been under your hood for something else?

I was asking if weak vacuum will cause the transmission to not go into OD, and what other things should I check as a possible cause for the TC to not lock up in OD. It just stays in 3rd gear.

OD and lock up are purely electric. Power is supplied to the center wire on the three wire plug on the transmission. The PCM provides the ground for each solenoid. Possible problems include a bad PCM, a bad OD solenoid, a bad OD to PCM wire, or maybe a bad TPS. Could also be an internal transmission problem. I'd start by manually grounding the solenoid wire and see if that engages OD.

I'd start by checking for voltage on the center pin when the ignition is on.
('cause I am lazy)

Ok thanks guys

Sense he didn't say lock up wasn't working, then I figured he has power to the solenoids.

@cougar
 

Looks like no OD and no lockup to me.

I have lock up in 3rd, but no OD. If I push the tow haul button I get TC lock.

OK, now you need to find out if the lack of OD is caused by the PCM not signalling for OD or the transmission ignoring the command.

You can do that by wiring a small (2-3W) bulb in parallel to the OD solenoid, so that you can watch the lamp while driving.
(I usually make a jumper cable with a male and a female plug that fits between the transmission and the plug coming from the vehicle. The bulb wires are zip-tied to the frame and come in through the driver side door. I use a green and a yellow bulb from a motorcycle .neutral and turn indicators)
If the light comes on and no OD- something wrong with the solenoid, or the hydraulics in the valvebody, or maybe even a worn out OD clutch piston seal.

No light- Try again with the alternator deactivated by removing and insulating the small red wire, because sometimes the reason is too much electrical noise.
If this fixes it, get new brushes for the alternator.