Automatic Transmission problems??

[acme1]

I have a 96 suburban k1500, the tranny works great when it is cold but I notice when it gets hot it starts to slip. I notice it more when I am at a cruising speed and i floor it, the tranny kicks down to a lower gear and revs high with no extra speed. If I let my foot off the gas it will shift back and then go. This happens when I am climbing a steep hill on the freeway as well, I try do go a little faster and end up going slower. I am wanting to buy a boat but i am scared that I wont be able to pull it. Is it possible for just one gear to slip on an auto tranny? I pulled the dipstick and the fluid is still red with no burnt smell. This is really frustrating me, I ask different mechanics that I know what they think and they all have conflicting answers. Should I use an additive? Any help would be great. The truck has 172000 miles on it and I just bought it 4 months ago.

[maxwedge]

For a proper diagnosis this truck should be road tested by a trans tech using a trans capable scanner to check for solenoid functions, gear error codes and slippage errors.

[acme1]

Where can I find a trans tech??

[2000CAYukon]

Please note that when you feel the transmission slip at cruising speed, the 3-4 clutches are wearing. If you keep driving it when it is slippling, a tranny rebuild will be the only way to fix it.

Valve body wear can cause line pressures to be reduced when hot and the 3-4 clutch pack does not have the same holding power and it will slip.

//2000CAYukon

[acme1]

would I need to do a trans rebuild to replace the 3-4 clutches?? What do I need to do to fix that?

[2000CAYukon]

All of the clutches (not just the 3-4 clutch pack) require the tranny to be out of the truck to be replaced.

Line pressure should be checked to see if it is within spec. Low line pressure can cause the clutches to slip under load.

The valve body can be removed without removing the tranny. The 3-4 Clutch pack is a weak link on the 700R4 (4L60) and 4L60E. A common upgrade when rebuilding is to go with more clutches and steels to make the 3-4 clutch pack stronger.

The Sunshell is also a weak link and is usually upgraded.

//2000CAYukon

[acme1]

I went to Autozone and got the codes from the check engine light, (it always came on when the tranny slipped) here are the codes P0131 sensor circut low voltage bank 1 sensor 1 and P0151 sensor circut low voltage bank 2 sensor 1, I checked the book and these are both oxygen sensors but does anybody know where these are located?? Also could this contribute to the problems I am having?? Those were the only codes to come up, any help would be great. Thank you.

[2000CAYukon]

If the tranny was slipping, it usually sets P1870. Engine issues can feel like tranny slipping.

Since the codes are both for the front sensors low voltage, power to them or the common ground is bad.

//2000CAYukon

[acme1]

where are the front sensors located on a 96 k1500 suburban 5.7?

[maxwedge]

In the pipes from the manifold to the cat.

[acme1]

Where is the common ground for the o2 sensors?

[acme1]

also would it be ok to jump the wires connecting a new 12 volt supply and ground?

[maxwedge]

Hold on here, the 12v supply is for the heater circuit only, the pcm controls these circuits. You can check the ground wire in those circuits for continuity check the plugs for corrosion but your description of the problem points to a trans issue, not this o2 code issue. Check this link for a diagnostic description. http://service.gm.com/gmspo/mode6/pd...t57R_CKGyE.pdf

[acme1]

why would the traany be fine until it gets hot and then start slipping?

[2000CAYukon]

Originally Posted by acme1

why would the traany be fine until it gets hot and then start slipping?

Valve body wear is the most common reason. Others include a bad pump or torque converter.

//2000CAYukon