Higher RPMs

[Mr Clean]

It is the strangest thing I went to work my truck runs about 2800 RPMs at 70mph, come home that night and it is running 3300 RPMs. I don't have a clue what would cause that. Truck seems to be running fine, Trans isn't slipping, does anyone have a clue what it could be?

 

[HotRodPC]

What Trans is it? Is it possible you're lock up conveter isn't locking up???

 

[Mr Clean]

700r4 do you think my wire came off?

 

[HotRodPC]

700r4 do you think my wire came off?

Not sure if a wire came off or what, but that is exactly where I'd start. I'd say its going to be a TC lock up issue. We're talking about 500rpm and that's about right for a lock up issue. Take it for a ride and pay attention trying to feel for the lock up to happen. I have a feeling you're not going to feel it.

 

[GreaseDog]

could be a headwind/tailwind situation too, with a little extra effort to move the truck into the wind, the parameters may not be right for locking the converter.

 

[HotRodPC]

could be a headwind/tailwind situation too, with a little extra effort to move the truck into the wind, the parameters may not be right for locking the converter.

Very True. If the motor is straining enough and not detecting enough cruising vacuum at the vac switch, it will never tell the TCC lock up solenoid to lock it up. Which reminds me of another thing to check if the TCC isn't locking up. Make sure your vac line hasn't come off the switch on the firewall. Nonetheless, this is likely a minor problem. Just find out if your TCC is locking up or not and we'll go from there.

 

[Mr Clean]

Very True. If the motor is straining enough and not detecting enough cruising vacuum at the vac switch, it will never tell the TCC lock up solenoid to lock it up. Which reminds me of another thing to check if the TCC isn't locking up. Make sure your vac line hasn't come off the switch on the firewall. Nonetheless, this is likely a minor problem. Just find out if your TCC is locking up or not and we'll go from there.

What vac line, I don't have a vac line to the trans. I guess I don't know what to feel if the trans goes into lock up. I checked the wire, and it is plugged in. We have had some bad weather here lately, when I go to work in the morning I'll see what it does. I did take it out for a ride today, and when I was doing about 70mph I goosed the motor, and the rpms dropped to 2900, but when I slowed down, and than went back to 70 they went back to 3300-3500. Should I call my tranny guy, it is still under warranty.

 

[HotRodPC]

Not a Vac line to the trans. A vac line to the lock up switch on the firewall closer to the passenger side.

 

[Mr Clean]

Not a Vac line to the trans. A vac line to the lock up switch on the firewall closer to the passenger side.

What does it look like? When I had the trans rebuilt, I run a wire from a keyed power to the trans, and that is it. I don't know what a lock up looks like or what it does.

 

[GreaseDog]

If you want to see I'd its locking, get up to cruise speed, and then lightly step on the brake pedal. Just enough to light the brake lights, but not enough to apply the brakes. Watch your tach when doing this.engine rpm should climb a few hundred rpm, if it its locking, as it should unlock as you step on the brakes

 

[HotRodPC]

Take a look at this part and the pic. Then look for this part on your firewall. It should have a vacuum line to it, then a wire that goes down to the trans 4 prong plug in. This is where the trans detects cruising and locks up the converter.

http://www.rockauto.com/catalog/moreinfo.php?pk=86939

 

[Mr Clean]

Take a look at this part and the pic. Then look for this part on your firewall. It should have a vacuum line to it, then a wire that goes down to the trans 4 prong plug in. This is where the trans detects cruising and locks up the converter.

http://www.rockauto.com/catalog/moreinfo.php?pk=86939

I don't have one of those. when the trans got rebuilt they changed it to a one wire

 

[Camo]

Did you count the number of time it shifted/locked up on a single take off. Tht will tell you if your shifting thru all the gears or not.

 

[Mr Clean]

Its shifting four times, I talked to my trans guy that rebuilt it, he said it is probably one of the servos, or a relay I forgot what he said. I have to take it to him next week, and they will look at it, and fix it.

 

[HotRodPC]

So with 4 shifts, then that is 1-2, 2-3, 3-4, and 4 to lock up. So it's a Servo???? uhhhhh OK !!! Lemme know how that turns out. hmmmm???

If that is true, I wouldn't be driving the truck. This would mean the higher rpm, is the trans slipping the whole time and that the servo isn't holding a band tight enough, and could be tearing up the band, and wearing a groove into a clutch drum.