Engineering Marvel Chrysler's A604 Automatic Transmission

[carcomp101]

Nice! Got it in one take! Great filmwork and information.

[nuttylb562]

sorry to bug! im wondering if my 99 chrysler concorde has the a604 tranny? it has 168,000 miles and its starting to make a grinding noise almost like the sound of dewalt 3000 rpm buffer. ive been very happy with my car and im wondering if i should just get a new one or should i just rebuild it? and also how much am i gonna have to spend to fix the noise and the slipping at the red lights?thanks for your time and i hope to hear from you soon.

[happy543210]

I guess the "marvel" is how small it is? Well, I bet for that size it handles very little torque--useful only for small 4 cylinder engines.

[larrybloodworth]

@happy543210 Yes, this is better than GM's design in that it's lighter and smaller. It is used not only behind 4 cylinders, but also large V-6's in heavy 4K lb.+ vehicles. It's only 7" long and the shortest GM overdrive is 15 inches long.

[happy543210]

I don't get it. Why is this a marvel of engineering? How is this any better than GM's "hydramatic"?

[larrybloodworth]

The clicking or buzzing sound are the PWM solenoids cycling when they turn a clutch on or off. The early 604s had a sound deadening shield over them. Often, some techncians leave them off.

Borg-Warner redesigned their solenoid pack for Chrysler and it doesn't make any noise and is now the OEM for the 604 solenoid packs.

[garthja]

Thank you

[blueovalfan23]

interesting. i got one in my car. while it sounds good and it is a decent automatic, i'm not completely impressed with it. i'm used to the older setups. i haven't had any trouble with it yet though and it's got about 175,000 on the car. i guess that should say enough. i wonder though what's with the clicking. i hear it in almost all dodges with a similar setup doing that when putting to.downshift. it's seems to be common. mine has done it from day one but it doesn't do anything funny either.

[larrybloodworth]

The "5th gear" some drivers perceive is not really a gear change. It's the torque converter clutch (TCC) applying.  A torque converter is normally not 100% efficient. There's about a 10% RPM loss between engine RPM and input shaft RPM. When the TCC applies, it mechanically couples the engine's crankshaft to the transmission input shaft, just like a stick shift manual transmission does when the clutch engages. Once the TCC is applied, the torque converter is 100% efficient.

[larrybloodworth]

No, it's not a 5 speed.  It's a 4 speed. 3 speed with overdrive.

Ratios:

1st Gear - 2.84 to 1 (underdrive)

2nd Gear - 1.57 to 1 (underdrive)

3rd Gear - 1 to 1 (direct)

4th Gear - .69 to 1 (31% overdrive)

Reverse - 2.21 to 1

[jasonmoore1900]

its a five speed, four speed plus overdrive

[larrybloodworth]

@jasonmoore1900

Not quite. It's a 4 speed, 3 speed plus overdrive.

[larrybloodworth]

It does not have bands or sprags. It does it's thing with 5 wet multi-disc clutch packs...sort of similar to a motor to a motorcycle clutch

[CoolasIce2]

good vid. So it uses 1 band, and 2 or 3 clutches to work?

[larrybloodworth]

@CoolasIce2

Just caught your question. No, this transmission does not have ANY bands at all; it's all clutches. Bands are used to hold a geartrain element stationary. Chrysler does it with this transmission by using clutches that are splined into the transmission case.

[CoolasIce2]

@OK Thanks. I see that you said it uses 5 clutches instead of bands and sprags. I don't like the idea of bands, but sprags are a lot simpler than clutches, as long as they hold and don't break.