Engine/Transmission (1994 - 1998) Auto Trans function

[JoshPeters]

Ok guys..... there is always someone looking for advise on an automatic tranmission. Now I'm not going to say go with anyone. All I'm gonna do is give you a breif run down of operation. Hopefully this clears up some things.



Torque Converter: The torque converter has a fluid coupling. To get an idea of how this operates it is like taking 2 fans and facing them towards eachother. Now turn one fan on. The other fan will turn due to the air movement. A converter works in a smilar fashion. The Different companies out there have found a way to make the second, non powered fan spin at a higher rate. They do this with the Stator. The stator changes the direction of the air flow. The stator dictates Stall Speed and converter effency.



Stall Speed: Remember when you were a kid... maybe you still are... . And you put your left foot on the brake, and your right on the gas to do a big old smokey burn out? Well now do the same thing, but don't let the tires break loose. The point where the engine revs to but does nothing. Is the Stall Speed. The stall speed is done within the converter with the Stator.



Planetary Gearset: A planetary gearset is a very strong gearset. It has 3 main parts. The annulus gear, the the planetary carrier and the sun gear. To explain this, think of hellical cut gear in the center, around it you have 3 smaller hellical cut gears and outside of that you have the Annulus gear. This looks more like a drum, inside it is where the small planetary gears run.



Clutches and Bands: The various clutches in our transmission are slightly different than most other transmissions. In the Overdrive(rear section) of our transmission there is a VERY large spring that holds the Direct clutch. The Direct clutch is applied even when the truck is sitting still. The Direct Clutch is used for 1st, 2nd, 3rd, and reverse. The only time the Direct Clutch is not applied is in 4th gear.

Overrun clutch and Overrun sprag is a simple one way clutch. They are 2 different assemblies that do the same job, but in different areas of the transmission The Overrun Clutch is in the rear of the main case of the transmission, it is used for 1st, manual 1 and manual 2. The Overrun Sprag is used in all forward gears in our transmission. It is located in the overdrive section.

The Bands: The Front band is applied in 2nd gear and 2nd gear Manual selection only. The Rear band is applied in Reverse and Manual 1st only. It is used in Manual first for engine braking.



Reverse: The Front Clutch, Rear Band and the Direct Clutch are applied

First: The Rear Clutch, the Overrun clutch, the Direct Clutch, and the Overrun Sprag

Second: Front Band, Rear Clutch, Direct Clutch and the Overrun Sprag

Third: Front Clutch, Rear Clutch, Direct Clutch and the Overrun Sprag

Fourth: Front Clutch, Rear Clutch, and Unapplies the Direct clutch and applies the Overdrive Clutch.



Manual First: Same as above, but applies the rear band for engine braking.

Manual Second: Same as above.



Front and Rear Band Adjustment: Torque to 72inch pounds, back off exactly 2 turns. Torque the locking nut to 35ftlbs.



I hope this helps you guys understand the function of the transmission a little better.



Josh

 

[fox]

Mostly correct!!!



My 5. 2 liter Grand cheroke won't stall at the same speed as my Cummins, using the same converter!



Applied torque is what you forgot.

 

[JoshPeters]

I was just tryin to stick with the Basic functions.



I don't know for sure if the Jeeps and the CTD's use the same converter..... if they do... that's probably why we puke them all the time.



Josh

 

[Rams-n-Hogs]

Thanks, Josh



That was very informative. Brought it to a level even I can understand.



Jim

 

[fox]

Josh , good job.

I was being critical and should of not done that.

Actually the converter is specific to the Cummins.

Some say it is a V-10 converter, but that is not the case.

 

[JoshPeters]

No problem Fox! I'm sure they must use a converter specifically for these trucks, the redline being as low as they are, and running the RPM they do at highway speeds... I think we are crusing at lower RPM than the Gassers stall!



Josh

 

[fox]

Yes, we are.

I really feel that Dodge identifed a cause of possible fairure early on with these truck and, instead of solving it, chose to go around it.

By that, I mean they knew these trannies were not putting the pressure to the correct clutch without some losses so the loosened up the converter to get some voluume.

This is the internal leaks that is so often discussed here.

What one does with some knowledge with these trannies is remarkable. We all say thanks to the guys who did the work to re-engineer these things and to share it is great.

I have an old 727 torque flite that has better machine work than the current trans have. That is hard to understand.

 

[Willys]

Thanks for the explanation. I'd like more information on the purpose of the bands, how they work, why they need adjustment, etc. thanks,



Andy

 

[JKouzez]

very informative i actuallly had the privalige of watching the guy who did my DTT put it together he showed me the DTT parts and stock parts there really is a big diffrence now that i read ths i understand even better how an old slush box works unless you have an aftermaeket transmission those arre no slush boxes at all.

 

[fox]

Willys, do you understand how a planetary gear set works?

This would be the best place for you to start. Do a search on it or get one in your hands and play with it.

The bands simply stop the ring gear from turning which changes the ratio thru the planet assembly.



Following the fluid flow thru a Valvebody is fascinating to me. The people who design them are brain childs.

By the way I don't completely understand them, but from reading these issues with our Dodges, few transmission guys know them but get paid well to bluff their way!!!!

 

[zstroken]

There is actually one more component to the planetary gear sets... the annulus gear.

You might want to clarify which transmission the band adjustments are for. the 47 and 48 use different adjustments.

 

[JoshPeters]

Usually when I discuss a Planetary gear set I think of the entire set, due to it will not work without all 3 components.



You are correct the band adjustments are slightly different. I will locate those adjustments and edit the first post.



Josh

 

[blkdragon]

Great explanation. I have been doing a lot of research on these trannies and these explanations really cleared things up for me. This is what makes this site so great. Great people and great advice. We CTD owners are so luckly to have this place. We not only have the best motors but who else has a site of this caliber?