2 4th-gear questions

[Toady]

1) I've been getting some strange readings from my scantool (Auto X-Ray). It indicates that 4th gear is always engaged, whether the tranny is in P, R, N, D, or...you get the picture. All other readings are right on, so is it bad to have 4th "on" all the time?

2) May be related: when the tranny is in D, the car decels differently from when it's in OD. Like coasting down in 3rd vs. 4th in a stick car. Is this normal?

I know I need a rebuild. Been planning for it since I met Bruce T. last year. Just want to know if I need to step up my efforts.

Thanks in advance,

 

[GNeric]

If the 4th pressure switch is bad, wire broken or disconnected, this will cause the 4th indicator to turn on. It really won't hurt anything but the computer will scale back the boost as if it was in 4th gear.

When the trans is in Overdrive, the overrun clutches aren't applied. There will be no engine braking this way. When in Drive position, the overruns are applied and you get the engine braking. This is normal.

 

[Toady]

Thanks for the info, Eric. I still have a question about:

When the trans is in Overdrive, the overrun clutches aren't applied. There will be no engine braking this way. When in Drive position, the overruns are applied and you get the engine braking. This is normal.

Is it still normal for this to happen at low speeds, like 35mph? I often drive around town in D so the car won't be "tempted" to hit 4th, but even going that slow, I've noticed if I bump the shifter back to OD while coasting, it's like I cut an anchor loose.

Rhett

 

[MeanBuicks]

That's correct. By shifting into OD, you are turning off the overrun clutches that are responsible for providing engine braking. Freewheel city.

 

[GNeric]

One of the coolest things about the overruns being "turned off" is that I can cruise at around 37mph in the OD position (in 3rd gear) and let off the gas. RPM drops to about 750 and when I get back on the gas, sounds like a pretty decent stall converter. If someone is with me or next to me, they think that is exactly what it is. Gets me some weird looks sometimes.

 

[Toady]

Greg, Eric, thanks again for the info.

when I get back on the gas, sounds like a pretty decent stall converter
It's nice to know something on my car actually works like it's supposed to...