InvisiBill
Active member
Out of the box test:
Under minimum throttle with selector in OD, let truck shift into 2nd.
As soon as it goes into 2nd gear, full throttle, it MUST immediately go back down into 1st. If it doesn't tighten TV cable one notch (1/16"). You don't have to hold it there long. Just enough to see it goes down into 1st.
Upshift speed test:
Gear selector in OD.
Under about 10% to 20% throttle look for:
1-2 shift at 11-14 mph
2-3 shift at 22-25 mph
3-4 shift at 44-53 mph
Note that higher % throttle will result in higher mph shift.
*Note*
TCC apply in 3rd and 4th after engine is up to 130 deg F. If you notice that your TCC isn't applying when the engine is cold, that is normal. Using converter slippage is how Hydramatic gets the fluid up to operating temp faster. Once your engine is up to 130 deg F or so, you'll get TCC engage.
To do a seat of the pants check for TCC engage.
Get truck up to 4th gear steady throttle with normal temp reached.
Keep your foot on the throttle, don't lift it, keep it steady. Take your left foot and tap on the brake pedal enough that it makes the brake switch engage. Some trucks you can hear the click of the switch. When this switch engages (only takes a tap) you'll see your rpms jump 200 to 300 rpm if your TCC is engaging.
Part throttle downshift:
Get truck at a steady 48 to 55 mph. You'll be in 4th.
Quickly push it to about 1/2 throttle.
It will do two things.
TCC will release.
It will shift down into 3rd.
Once you have heat cycled the trans a few times (this also gets all the air pockets pushed out), do the next test.
Full throttle downshift:
Again, get a steady 48 to 55 mph. 4th again.
Floor it.
TCC will release.
Transmission will downshift all the way to 2nd gear.
There will be a much more noticeable pause than there was in the 50% throttle test. This is because it takes longer to let the 2-4 band release, let the 3-4 clutches completely release, then clamp the 2-4 band back down. The delay is intentionally programmed into the separator plate and spring rates to allow this to happen without damage. Drilling big holes too big in the separator plate doesn't allow this pause to take place. Kaboom.
Coast down test.
With shifter in OD, get into 4th and steady speed so TCC applies. 55 mph is fine.
Comppletely let off the throttle and LIGHTLY press on the brake.
TCC will release.
4-3 coast down speed: 35-47 mph
3-2 coast down speed: 13-21 mph
2-1 coast down speed: 8-10 mph
4-3 sprag and overrun test.
Get to steady 4th gear speed of 48 to 55 mph.
It is important that you let it get into a steady speed in 4th when you do this test or you can damage the sprag.
After steady speed is reach, completely release the throttle and pull the selector down from OD to D.
Three things should happen.
TCC release.
Trans should immediately shift to 3rd.
Engine should slow truck down due to application of overrun clutches.
Under minimum throttle with selector in OD, let truck shift into 2nd.
As soon as it goes into 2nd gear, full throttle, it MUST immediately go back down into 1st. If it doesn't tighten TV cable one notch (1/16"). You don't have to hold it there long. Just enough to see it goes down into 1st.
Upshift speed test:
Gear selector in OD.
Under about 10% to 20% throttle look for:
1-2 shift at 11-14 mph
2-3 shift at 22-25 mph
3-4 shift at 44-53 mph
Note that higher % throttle will result in higher mph shift.
*Note*
TCC apply in 3rd and 4th after engine is up to 130 deg F. If you notice that your TCC isn't applying when the engine is cold, that is normal. Using converter slippage is how Hydramatic gets the fluid up to operating temp faster. Once your engine is up to 130 deg F or so, you'll get TCC engage.
To do a seat of the pants check for TCC engage.
Get truck up to 4th gear steady throttle with normal temp reached.
Keep your foot on the throttle, don't lift it, keep it steady. Take your left foot and tap on the brake pedal enough that it makes the brake switch engage. Some trucks you can hear the click of the switch. When this switch engages (only takes a tap) you'll see your rpms jump 200 to 300 rpm if your TCC is engaging.
Part throttle downshift:
Get truck at a steady 48 to 55 mph. You'll be in 4th.
Quickly push it to about 1/2 throttle.
It will do two things.
TCC will release.
It will shift down into 3rd.
Once you have heat cycled the trans a few times (this also gets all the air pockets pushed out), do the next test.
Full throttle downshift:
Again, get a steady 48 to 55 mph. 4th again.
Floor it.
TCC will release.
Transmission will downshift all the way to 2nd gear.
There will be a much more noticeable pause than there was in the 50% throttle test. This is because it takes longer to let the 2-4 band release, let the 3-4 clutches completely release, then clamp the 2-4 band back down. The delay is intentionally programmed into the separator plate and spring rates to allow this to happen without damage. Drilling big holes too big in the separator plate doesn't allow this pause to take place. Kaboom.
Coast down test.
With shifter in OD, get into 4th and steady speed so TCC applies. 55 mph is fine.
Comppletely let off the throttle and LIGHTLY press on the brake.
TCC will release.
4-3 coast down speed: 35-47 mph
3-2 coast down speed: 13-21 mph
2-1 coast down speed: 8-10 mph
4-3 sprag and overrun test.
Get to steady 4th gear speed of 48 to 55 mph.
It is important that you let it get into a steady speed in 4th when you do this test or you can damage the sprag.
After steady speed is reach, completely release the throttle and pull the selector down from OD to D.
Three things should happen.
TCC release.
Trans should immediately shift to 3rd.
Engine should slow truck down due to application of overrun clutches.
