That's a lot of transmissions. How many miles are on the truck?

 

What transmission did you put in? I went from a 4R100 to a HD4R100.

When you say it's been doing this for 120,000 miles, is that how long you've had the truck, or did something change then?

 

truck has 220k now, I bought it at 100k.

All those parts (including all transmissions) were replaced within the past month. To be fair, one tranny had a bad pump and only went 3 miles.

 

This seems to be the right thread for this.

I was driving around yesterday with the AE hooked up and just out of curiosity I monitored the tranny Turbine Shaft Speed (TSS), Output Shaft Speed (OSS) and the Torque Converter Slip Actual. At speed in Overdrive when the TSS was reading approximately 1500 RPMS the OSS was reading approximately 2100 RPMS.

It was too difficult to watch the road and the live data monitors so using rounded off RPM readings of 1500 divided 2100 you get 0.714. The 0.714 matches close enough the Overdrive ratio of 0.71:1 so the tranny was definitely in OD. Turning off OD both the TSS and OSS RPMS were the same, as should be expected - 3rd gear ratio is 1.00:1.

TC Actual Slip was 1 RPM which essentially means the TC was locked.

4R100 Gear Ratios:

1st - 2.71:1
2nd - 1.54:1
3rd - 1.00:1
4th(O/D) - 0.71:1

 

Great post Robin. Its great that somebody would go out and do that for comparison. That should give him something to work with. His RPM's just seem wrong for the diff., at that ratio.

Chet

 

This is crazy....I'm on 305/75/16 and run about 2000 RPM at approx 68-70 MPH. 6-speed transmission.

Just throwing this out there, but would it be possible that you are only making it into Third gear and something is messed up electronically so it down shifts with the OD button but you are not ACTUALLY getting into OD?

Also, maybe you got a different tranny that has a different OD ratio? You said the last 2 were used ones, were they taken out of F250/350? or were they just 4R100 transmissions?

Hope you get this taken care of. Another idea, and again im just thinking of anything that would make sense to me, is it possible that your tranny is outputting the correct amount and youre diff is fine, but you have something sticking between the diff and the ground that is preventing your wheels from moving at a certain speed? IE a stuck break or something like that?

 

Not really so great of me because I was actually out driving around trying to find an intermittent problem (LINK to Post 23 and Post 35 Follow Up). But while out there I remembered this thread and did the TSS/OSS reading comparison.

 

Did you see my post 34. Shows how to determine if the tranny is in OD or 3rd using AE and a little math. This will work with any scan tool that will read TSS and OSS rpms.

 

Computer showed my tach is off. 30rpm at idle and close to 300 at 2500