Big transmission dilemma

[SteveSRT8]

Originally Posted By: Gary Allan
Quote:
My particular car can go from 5% on up, and in any gear but first and reverse. It does that by regulating the duty cycle of the solenoid controlling that fluid passage.


Do you have a linkable overview for this process? I can't see that doing anything other than creating incredible wear and chatter/shudder ...but that's just my reasoning due to my acquaintance with the most common tcc's


Gary, it's nothing new. This is the NAG1, a derivative of the WA580 Mercedes 5 speed. Been in service since like 2000 or so.

Lots of modern cars do this, both FWD and RWD, it's a very common strategy now. No longer just an on/off part!

 

[friendly_jacek]

Originally Posted By: SteveSRT8


Gary, it's nothing new. This is the NAG1, a derivative of the WA580 Mercedes 5 speed. Been in service since like 2000 or so.

Lots of modern cars do this, both FWD and RWD, it's a very common strategy now. No longer just an on/off part!


I would like to see the links, too. Want to learn something new.
Mind you, the discussion is on specific toyota/AW trannies.

 

[Gary Allan]

There's going to have to be some real revelation in concept. I'd love undummy to chime in. What's effectively being suggested here is (literally) micro-grabs. It's gonna be a true education for this to evolve from something that's been a curse to a virtue. Now for the ultimate in pressure manipulation for infinitely variable shift firmness ..from velvety smooth (let me find the first marketing weasel ..let me get my hands on him) to WOT snap shifting ..sure.

 

[Gary Allan]

Quote:
Changing those really won't gain any faster shifting, the real answer lies with the Line Pressure Variable Force Solenoid and the Shift Pressure Varible Force Solonoid which are Pulse Width Modulated. Changing those change everything and IMHO with a little valve modification also


I'll be happy to entertain other points of view ..but this is enough for me.


http://www.cherokeesrt8.com/forums/showt...7590&page=4

 

[unDummy]

Its not infinitely variable shift firmness. Its infinite variable shift smoothness.

If the TC doesn't unlock, it causes compression braking when you don't want it to. You can override the TC programming with a manual downshift.

Worst case lockup scenario was in RWD Fords without ABS which would stall when you slammed on the brakes since the TC didn't unlock quickly enough.

If the TC doesn't unlock, it causes an abrupt shift. You can tune the slippage to eliminate or counter the abrupt shift.

If the TC does lock instantly(popped clutch effect), its too abrupt for the typical consumer, most who don't know what a manual transmission is!!!

If the TC doesn't lock. You throw away MPG and create heat. Remove heat with larger sumps, bigger coolers...... and we know that nothing is over engineered! And, MPG is critical if you don't want the envirohippies picketing in front of your house.

Can't have a fixed curved for the lock/unlock process. Its tuned for fluid temp, engine rpm, throttle position, speed...... ALL for the sake of that SMOOTH shift.

Instead of thinking it as a variable clutch slippage, think of it as a variable stall TC using the 'clutch slippage' to mimic multiple TC's at the same time, as needed. Full lockup for MPG. Full slippage to get RPM up for pass power. And, variable slippage curve for everything in between.

Also, since engine power is variable, there is no need to load up the lockup clutches if power going to it is minimal. No wasted fluid flow or pressure!!!! So, if at a low throttle position, then you can use low duty cycle to get the lockup you need. In the ol' days, it was all or nothing. You would lockup the converter(and transmission band/clutches) with enough pressure for the full engines output even if you were cruising at 1/4 throttle. Why waste HP/MPG on full lockup when you weren't at full power?

BTW, my last new car purchase earlier this year had an old school manual transmission and clutch. Slip control converters(along with slip control gear changes) are something I do not care for. But, the typical consumer, and every auto magazine, does. All they talk about is the seamless shift. If the shift can't break a u-joint, then its for old people.