Re: [A/S] Cummins 24 valve Torque converter

[Jim Dunmyer <jdunmyer@xxxxxxxxxxx>]

Mark,
  Here's how my '94 works, and I'd imagine yours is similar:

Start out at light throttle and just let it do its thing. It'll shift 1 
-> 2 very quickly, then 2 -> 3 at about 15-20 MPH. The 3 -> 4 shift 
won't happen much below about 35-40 MPH. The TCC locks at 50, but it's 
been in 4th for some time. If you leave off the throttle completely, the 
TCC will unlock; if you touch the brake with your left foot, the TCC 
will unlock. Take your foot off the brake and the TCC will re-lock, as 
long as you're still above 50 MPH.

Try going down the road at a steady 55 or so, then do the left foot on 
the brake trick, watch the tach, and listen to the engine. Mine's noisy 
enough (no muffler, just the cat) that I can easily tell exactly what 
it's doing.

Push the OD lockout and it will: Unlock the TCC, downshift to 3rd, then 
lock the TCC. Push the button again and the TCC will unlock, the 
transmission will shift to 4th, and the TCC will re-lock. Again, as long 
as you're above 50 MPH.

Some of this is easier to see/hear when the truck is under load, IE 
towing your trailer. When it's totally unloaded, the TCC lockup can be a 
bit hard to determine, especially in 3rd, as there's not a lot of TC 
slippage. It's a different story in 4th; mine drops about 500 RPM when 
the TCC locks in 4th, it sounds just like a shift to "5th".

If the transmission temperature is below 60, the TCC will NOT lock. In 
cold weather, this it can take a mile or more for the temperature to 
exceed 60.

Play around a bit and you'll soon be able to tell exactly what's going on.

                                  <<Jim>>