Is this normal for transmissions to shift like this?

[Chris B.]

I have noticed this in most of the cars/trucks I have owned. Most recently in my 2003 Silverado and 2002 Camaro. If I'm driving slowly(20mph or less) and I gas the car/truck slowly it shifts smooth and quiet but if I gas it medium to stomping on it it down shifts much harder. It sounds like it is slamming into gear with a "clunk". The car/truck will not do this at higher speeds above 30 or highway speeds when you step on it. When it does this it kind of feels like thare is a little "play" in the gears and that is maybe where the clunk is comming from. I think it is normal as all of my cars/trucks over the years have done it about the same and I have been told it is fine like this but I was wondering what you guys thought. Do transmissions shift harder at lower speeds when you get on it and why not at higher speeds!

As always thank you for the help!

 

[Dan4510]

Chris,

I can only comment on this about older mopar transmissions, cause that's all I know about.

On the older mopars, there is a kickdown linkage that mechanically links the throttle and the transmission. Position of the kickdown linkage directly affects fluid pressue in the valve body.

When there is light throttle pressure on the tranny, fluid pressure in the valve body is low. Thus easy smooth shifts.

When throttle pressure is upped by pushing the accelerator 1/2 to 3/4 throttle, fluid pressure is greatly increased, so the valves controlling the shift have greater pressure on them, move faster, thus a harsher shift.

I dont know how this would apply to an electronically controlled tranny.

Dan

[ August 21, 2003, 10:02 PM: Message edited by: Dan4510 ]

 

[timzak]

On light acceleration, the car automatically downshifts one gear or not at all (keeping the current gear), therefore engine RPMs stay relatively low and the downshift (if there was one) is less dramatic-feeling. On full throttle acceleration from a low speed, you are probably already cruising in 3rd gear, so it downshifts two gears to 1st. The result is a near-instanteous HIGH increase in engine RPMs, and much more dramatic "clunk". I may be mistaken, but the clunk sound may be coming from the torque converter (please correct me if I'm wrong someone) undergoing much more stress than a mild downshift.

 

[jsharp]

Most are designed to shift slowly and smoothly when it's acceptable to do so. But at high RPM or with high loads they can't shift slowly and keep the engine from overreving or the transmission from slipping too much in between gears...

 

[Chris B.]

Thanks for the replys guys!
So what would a little clunk/chang be when driving slowly and coasting and then hitting the gas a little and it feels like a little bit of play in the drive line with out the transmission shifting. It happends only when I tap the gas just right? It does this in all my cars.

 

[Dan4510]

Chris,

You are putting slack into the drivetrain when coasting. Then when you get back on the gas, all the slack is taken out and you have a clunk again.

sort of like unwinding rubber band and having to wind it back up again.

Dan

 

[Drew]

My transmission on my 1992 Nissan Stanza started clunking badly on a forced downshift at 3/4 throttle only with a down shift into 2nd gear.

Tranny had AMSOIL ATF fluid w/ aftermarket cooler. Did a powerflush and fluid was burnt with only 15k highway miles on it. Pieces of roller bearing were found on the magnetic drain plug.

I have owned 16 Nissans (newer and older than this one) and never had a auto transmission fail before 170k miles. This is the first time I have used AMSOIL ATF and I will never use it again.

The clunking you are feeling is bad news. Flush your transmission fluid, refill it and add a bottle of LUBEGUARD.

Take care,
Andy

 

[Mike_dup1]

Did you put LUBEGUARD in with the Amsoil????

If a trans (or any component for that matter) is functioning normally and in good mechanical condition there is no reason to add any additives to the lubricants. Sometimes they can do more harm than good.

[ August 23, 2003, 08:26 AM: Message edited by: Mike ]

 

[Chris B.]

quote:

---

Originally posted by Dan4510:
Chris,

You are putting slack into the drivetrain when coasting. Then when you get back on the gas, all the slack is taken out and you have a clunk again.

sort of like unwinding rubber band and having to wind it back up again.

Dan

---

So this is perfectally normal?

[ August 24, 2003, 11:37 PM: Message edited by: Dan4510 ]

 

[Chris B.]

quote:

---

Originally posted by Drew:
My transmission on my 1992 Nissan Stanza started clunking badly on a forced downshift at 3/4 throttle only with a down shift into 2nd gear.

Tranny had AMSOIL ATF fluid w/ aftermarket cooler. Did a powerflush and fluid was burnt with only 15k highway miles on it. Pieces of roller bearing were found on the magnetic drain plug.

I have owned 16 Nissans (newer and older than this one) and never had a auto transmission fail before 170k miles. This is the first time I have used AMSOIL ATF and I will never use it again.

The clunking you are feeling is bad news. Flush your transmission fluid, refill it and add a bottle of LUBEGUARD.

Take care,
Andy

---

What do you mean by bad news? Both cars are basicly brand new with less then 12,000 miles on them. I can't see how both transmissions could be bad already and both act the same as well as my older cars.

 

[tom slick]

i think GM has a service bulletin out on that problem. it replaces the tans. yoke and uses some special grease?

 

[Ray H]

My dad had a go-to-work beater '52 Chevy with Powerglide that NEVER upshifted or downshifted harshly. It was stuck in high gear and had the option of reverse. Felt like a then-current era Buick Roadbastard.

 

[Dan4510]

quote:

---

Originally posted by Chris B.:

quote:

---

Originally posted by Dan4510:
Chris,

You are putting slack into the drivetrain when coasting. Then when you get back on the gas, all the slack is taken out and you have a clunk again.

sort of like unwinding rubber band and having to wind it back up again.

Dan

---

So this is perfectally normal?

---

Chris,

Yes, this is normal. All drivetrains have slack and will act like this depending on how much slack. Slack is normal.

Dan

 

[mf150]

I have just the opposite problem. I have a manual 5 speed 2003 Mustang GT. The thing grinds at low speed shifts, but smooths out at higher rpms. Oh, yeah, I have a Ford...that explains it all! lmao

 

[jsharp]

quote:

---

Originally posted by mf150:
I have just the opposite problem. I have a manual 5 speed 2003 Mustang GT. The thing grinds at low speed shifts, but smooths out at higher rpms. Oh, yeah, I have a Ford...that explains it all! lmao

---

Dunno if Ford had changed this yet but they should have a long time ago.

Throw away the junk plastic clutch quadrant/adjuster mechanism and get an aluminum quadrant and a firewall adjuster. Adjusted correctly, the clutch will actually disengage and the shifting is much improved.

It's one of the best things I ever did for my 5.0L...

[ August 25, 2003, 12:51 PM: Message edited by: jsharp ]

 

[QuadDriver]

an auto transmission is always 'in gear' when in gear....the actual gearing is done by planetary sets which are always meshed and the power routing is done by clutches that either slip or grab.....the clunk is in the output yoke, ujoints or rear end - but dont worry about it until the U's loosen up. chevy rears always havea bit more lash than others.

as for the firmness of the shifts, on E trannys, throttle pressure is inferred from a cable or tps output, mashing the gas sends throttle pressure to the max and raises line pressures to expedite the appropriate shift to proper gear (governor output) and since the engine is climbing in rpm and power at its max rate, the apply of the clutch is gonna be firmer than normal.

 

[Chris B.]

Thanks again! I was hoping that I wasn't going to have problems with both my transmissions also!

 

[crashz]

I second what QuadDriver said. Plus an overlooked item is the transmission pump is pumping more fluid at a higher line pressure when revving. This will activate the shift solinoids more harshly and also cause a fluid hammer effect.