45-55 mph

[_nickjoseph]

When I’m cruising and get between 45-55 I feel the truck jump at 45 and then the power is more sluggish and the exhaust has a choppy sound- vibrations.

 

[slowburb]

Torque converter clutch? Lockup maybe?

 

[_nickjoseph]

Torque converter clutch? Lockup maybe?

What do i do?

 

[Schurkey]

What do i do?

Start by describing WHAT YEAR, WHAT MODEL, WHAT ENGINE, WHAT TRANSMISSION, and WHAT GEAR RATIO your truck has.

We're not mind-readers.

Yeah, it's likely the torque converter clutch engaging, possibly with an engine that doesn't run properly.

 

[_nickjoseph]

Start by describing WHAT YEAR, WHAT MODEL, WHAT ENGINE, WHAT TRANSMISSION, and WHAT GEAR RATIO your truck has.

We're not mind-readers.

Yeah, it's likely the torque converter clutch engaging, possibly with an engine that doesn't run properly.

1997 k1500 5.7l vortec with the 4l60e and 3.42 gear

 

[_nickjoseph]

Any idea

Start by describing WHAT YEAR, WHAT MODEL, WHAT ENGINE, WHAT TRANSMISSION, and WHAT GEAR RATIO your truck has.

We're not mind-readers.

Yeah, it's likely the torque converter clutch engaging, possibly with an engine that doesn't run properly.

Any ideas? It’s only from 45-55

 

[Supercharged111]

My 88 would misfire around 45 and 45 only. Turned out one of my plug wires wasn't making good contact so I squished it a little with pliers and problem solved.

 

[L31MaxExpress]

1997 k1500 5.7l vortec with the 4l60e and 3.42 gear

Sounds like its locking up in overdrive. If you have taller than stock tires, asuspension lift or a body lift this can be exaggerated.

You can either move the shifter down to 3rd until you get to a high speed or have the PCM reprogrammed to delay the 3-4 upshift to higher speed. I prefer to program the PCM to shift like this at approximately 25% throttle.

1-2 shift = 22 mph
2nd lockup = 28 mph
2-3 = 42 mph
3rd lockup 45 mph
3-4 = 55 mph
4th lockup = 65 mph

It will keep you in the 1,800-2,500 rpm range during acceleration while keeping converter slippage to a minimum.

 

[_nickjoseph]

My 88 would misfire around 45 and 45 only. Turned out one of my plug wires wasn't making good contact so I squished it a little with pliers and problem solved.

It only does it under slight throttle so this may be it

 

[L31MaxExpress]

This is how the response is shifting at the equivalent rpm. 99 Suburban with 3.42s and P235/75R15s at the time. Had a F-car LT1 cam and S10 torque converter. Was running slightly uphill at about ~20% throttle in this clip.

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[_nickjoseph]

I have

Sounds like its locking up in overdrive. If you have taller than stock tires, asuspension lift or a body lift this can be exaggerated.

You can either move the shifter down to 3rd until you get to a high speed or have the PCM reprogrammed to delay the 3-4 upshift to higher speed. I prefer to program the PCM to shift like this at approximately 25% throttle.

1-2 shift = 22 mph
2nd lockup = 28 mph
2-3 = 42 mph
3rd lockup 45 mph
3-4 = 55 mph
4th lockup = 65 mph

It will keep you in the 1,800-2,500 rpm range during acceleration while keeping converter slippage to a minimum.

I have 33” tires and like a 2” lift. When I’m going the speed limit under slight accel. At 45 it jumps then starts the choppy exhaust sound and loss of power