Very Strange Change

[ubtripn]

I have been watching my tach very carefully and also using a gps speedometer and yesterday I experienced a definite change.

2100 RPM's was 65.

Yesterday and today 2500 is now 65 and my OD is still working. Nothing was changed. It is so strange to me but like I learned with my temp issues, start with the gauge accuracy but it isn't bouncing our anything so I just don't know.

I hooked up the OD on my 700R4 a few weeks ago and felt the change, it is definitely still working.

Someone once told me how to identify my rear end gear ratio so I am going to do that. I still cannot figure this out, truck still runs good though. Anybody ever experience the same thing?

[Overdriven]

Do you have a lockup torque converter? A lockup converter will usually drop about 300-400 engine rpm when it locks up since it's not slipping like a normal converter. If you do have a lockup converter I'd start there as it sure sounds like the issue. Sorry but I have no idea about diagnosing the issue. All I know is the converter usually locks up in overdrive at highway speeds.

[kwmech]

Recheck the adjustment on the TV cable and the wire going to the trans. Make sure the wire still has power with the key on

[ubtripn]

I checked that since I just got the OD working a couple of weeks ago, that was my first thought as well but it is definitely engaging.

[Bigdav160]

Lockup is usually 150-200 rpm change. Sounds like it's not going into fourth.

[ubtripn]

I am going to go out and do two more runs to count them out. Thank you all.

[kwmech]

If everything is working correctly, driving down the road if you lightly step on the brakes you should feel the torque converter dis-engage and lock back up when you release the brake pedal.