The 5.0 RPM difference is meaningless. Ignore it.

When accelerating it's normal to see torque converter slip as high as about 2,000 RPM.

 

Thanks again for your expertise Mark. Bypass swap it is. I'll post back with results after I replace it. Fingers crossed.

 

Bypass replaced 2 days ago. Really quite simple. 20 mins tops. I have driven it at highway speeds for 40 mins as well as stop and go from 0-55 and back to zero for roughly 40 mins. Not towing. Outdoor temperatures were 101-105 here in Vegas. Transmission temps get as high as 225 maybe 230 then seem to settle between 195 and 225. My best guess is that the old bypass failed. Any way to take the old one apart and verify that?

I still feel what I am interpreting as some slippage between 2nd and 3rd when I get on it a little (but not WOT) I think but I may just be on heightened alert. ***Disclaimer most daily driving done with DPTuner in 80HP econo.***

More questions: Remembering that this truck is on its original tranny at 160,000 miles...Should I install the new 6.0 cooler? The tranny has to be near the end of its service life right? If I install the new cooler I imagine installing a magnafine filter pre cooler would prevent any blockages in the new cooler when the tranny finally craps out or is that just pie in the sky thinking?

Also fluid was changed using Marks revised method roughly 1500 miles ago and it is no longer nice and bright. More of a deep burgundy color. I expect due to the high temps that I was seeing or maybe I didn't get all of the old fluid out. A lot of the old fluid came out of the rear port when I did the fluid change. It made a real mess and I think 20 quarts of the new ATF filled up the transmission rather than the suggested 22 if I remember correctly. Do I bite the bullet and change the fluid again? Mobill 1 ATF is not exactly cheap. Would really hate to waste all of the most recent ATF, a new batch of ATF, and a new 6.0 tranny cooler in short order particularly if the transmission goes South in the near future.

Am I thinking about this the right way or am I way off base?

 

Yes and no. You can take it apart. The usual failure mode is that the spring loses it's load. So you will need to find the specified load at the specified height and measure it. I never knew those specs so I can't help you with it.

Not necessarily. I've seen these transmissions run well over 300,000 miles.

That should work.

Fluid coming out of the rear of the trans indicates that the bypass has failed or the coolers are restricted. The trans holds 18 quarts. It usually takes 20 quarts to do a complete flush.

I wouldn't think so. Mobil 1 can take a lot of abuse.

 

Thanks again Mark. Last question for now...I think.

Would you recommend a Magnefine filter or spin on kit like the one on dieselsite?

 

I have no experience with either one. The Dieselsite one looks like it would perform better, but I've never tried it.

 

I am running a Magnafine filter. It is mounted pre-cooler for the reason you stated, to protect the cooler. I had previously overheated the trans so the cooler needed protection from any gunk remaining after I flushed the trans. Mount it where you can see it, like near the wheel well. After about a year the first filter developed a seep near the top. The replacement filter has been dry for several years now.

 

David,
I mounted a Magnafine filter on mine however it is after the cooler as it was a used one. I have had zero issues and it has been two or three years now, but I am tempted to change it out and open it up just out of curiosity.