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A904 Transmission Freshen Up
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Author:  Davey [ Sun Jul 08, 2007 5:53 am ]
Post subject:  A904 Transmission Freshen Up
LOOoong post...

The tranny presently in my D100 has been leaking fluid at a prodigious rate 'cause it took a hit and the case got cracked, so I went and got another one yesterday that came from running '70 Dart. I know this is a tranny out of an A body and under normal circumstances would not fit in a D100, but the engine/tranny in the truck now is from an A body so the trannys are a direct swap (I measured overall length just to be sure). I have some questions about freshening this new transmission up:

Torque converter removal: Looking at the front of the transmission, the engine would normally drive it in the clockwise direction. So, to remove the converter, I turn it about an eighth of a turn in the CCW direction, and it should pull straight out. Correct?

Torque Converter status: Are there any checks that can be performed on the converter? I would like to drain, refill and reuse the one on the new transmission, but wouldn't know how much fluid to put back in it. I see the drain plug to drain it...to refill it do I just install it and let the pump refill it?

I intend to replace the front seal and bushing while I have the converter out.

Charlie_S told me about the torque converter control valve in the valve body in another post. I will look at an exploded diagram at NAPA where I work and see where this valve is located. Is changing it out a simple task?

Valve body maintenance: Anything to be done here other than new filter?

Rear seal will be replaced.

Refilling the transmission with fluid: If I drain the converter and drop the pan, the tranny will be just about completely drained of fluid, correct? (I am thinking the only fluid left would be trapped in lines and passages). How best to service the tranny once I have it installed in the truck? Add about three quarts, then start engine in neutral, and add fluid until I sneak up on the full mark?

I know this is a long post, but appreciate your input. The torque converter is the biggest unknown to me. I don't know what to look for when inspecting an old one, and don't know whether to use the one that is in the tranny I'm removing, the one in the tranny I just bought, or go buy a newly remanufactured one. Again, thanks for your help on this. Davey
Author:  SlantSixDan [ Sun Jul 08, 2007 9:13 am ]
Post subject:  Re: A904 Transmission Freshen Up
Quote:
Torque converter removal: Looking at the front of the transmission, the engine would normally drive it in the clockwise direction. So, to remove the converter, I turn it about an eighth of a turn in the CCW direction, and it should pull straight out. Correct?
No eighth-turn needed; it'll just pull right out of the trans.
Quote:
Torque Converter status: Are there any checks that can be performed on the converter?
Not on the benchtop, no, not really.
Quote:
I would like to drain, refill and reuse the one on the new transmission, but wouldn't know how much fluid to put back in it. I see the drain plug to drain it...to refill it do I just install it and let the pump refill it?
Yep!
Quote:
I intend to replace the front seal and bushing while I have the converter out.
Smart thinking.
Quote:
Charlie_S told me about the torque converter control valve in the valve body in another post. I will look at an exploded diagram at NAPA where I work and see where this valve is located. Is changing it out a simple task?
Reasonably simple if you can find a replacement. Since you're going to be taking things apart, it might be a good time to install a Transco/TransGo TFSC kit, which I think comes with a new one of these valves and in any event fixes the drainback problem caused by a faulty torque converter control valve.
Quote:
Valve body maintenance: Anything to be done here other than new filter?
Give it a careful lookover while you're working with it. If you find a significant amount of "mud" in the passages, it'll need to be disassembled and cleaned.
Quote:
Rear seal will be replaced.
Another good idea. You'll also want to do the shift & kickdown shaft seal.
Quote:
Refilling the transmission with fluid: If I drain the converter and drop the pan, the tranny will be just about completely drained of fluid, correct?
Yes.
Quote:
Add about three quarts, then start engine in neutral, and add fluid until I sneak up on the full mark?
Three or four, then proceed as you guessed, yes. But (per your other post) you may want to rethink your intent to use Type-F fluid. Sure it works, but it's also an archaic fluid. Other fluids have greatly surpassed it in just about every performance aspect: Lubricity, sludge resistance, varnish resistance, thermal stability, anti-wear, anti-foam, viscosity maintenance, consistency and maintenance of frictional characteristics, etc.

Chrysler's transmission engineers wrote extensively on transmission fluids some years ago in this detailed paper. The focus is on fluid performance from the perspective of keeping A604s alive, which constitutes highly abusive service even if the vehicle is only ever used to go fetch a carton of ice cream from the store. But the various performance aspects of trans fluid are discussed and different fluids compared. It's worth a read.

Yes, you can get harder shifts with Type F. No, that doesn't necessarily mean you're doing your transmission any favors by using it.
Author:  dakight [ Sun Jul 08, 2007 10:35 am ]
Post subject: 
Hard shifts are often equated with transmission shifting efficiency but that isn't necessarily the case. Manufacturers have softened shifts by programing in some "overlap" which means that the next gear is selected and engaged miliseconds before the previous gear is released. The the extent that overlap can be decreased firmer shifts may help improve the performance. On the other hand, if the shift is too hard or the transmission allowed to race between gears resulting in a hard engagement then the shock and stress on the mechanism is substantially increased and may actully result in slower times as well as decreased transmission life. A hard shift may feel like better performance but that is not necessarly reflected in the numbers measured by the clock.
Author:  Davey [ Sun Jul 08, 2007 2:35 pm ]
Post subject: 
Great info guys. Thanks! I don't really care about "hard" shifts, and I did understand that firm shifts don't necessarily represent an "healthy" tranny, but your points are well taken.

I guess my question is, if I don't use ATF type F, what should I use? My truck sees no racing or hard service, just back and forth to work and a trash run now and then. Would Dex III be a better choice? I was trying to stay away from the MOPAR mixes like +4 or +5...they are pretty expensive from what I've seen. Of course, once I get the new tranny in I won't be pouring fluid thru it like I am now. I drove four hours at 65mph yesterday and used nearly a quart and a half of fluid with the present tranny in my truck. This is why cheap old type F was my choice.

Dan, I read the info about the transgo shift kit. Do you know if this kit can be installed from underneath the vehicle with the tranny installed? I couldn't tell from their info whether it involved any work to the front of the tranny, or just in the pan area. Davey
Author:  SlantSixDan [ Sun Jul 08, 2007 3:37 pm ]
Post subject: 
Quote:
I guess my question is, if I don't use ATF type F, what should I use?
I run Mopar ATF+4 in my old Torqueflites. It is costly, but superior to any variety of Dexron in just about every way. But, it is also better than necessary. Use it if you want the best, but don't lose any sleep picking a good brand of Dexron instead. Do not use ATF+3, which is not a good fluid. There is no ATF+5.
Quote:
Dan, I read the info about the transgo shift kit. Do you know if this kit can be installed from underneath the vehicle with the tranny installed?
The valve body needs to be removed from the transmission. The kit installs in/on the valve body; no modifications are made to other parts of the trans.
Author:  Davey [ Sun Jul 08, 2007 5:53 pm ]
Post subject: 
I was thinking Mercon Five when I said plus five...I knew better. If the transgo kit installs only on the valve body, this can be done with the truck in the vehicle, can't it? Davey
Author:  SlantSixDan [ Sun Jul 08, 2007 5:58 pm ]
Post subject: 
The valve body has to be removed from the trans, but the trans can stay in the vehicle.
Author:  BigBlockBanjo [ Tue Jul 10, 2007 7:50 am ]
Post subject:  More info!
Hey Dan,
The article on tranny fluid is great, you wouldn't happen to have a similar thing on engine oils, would you?? :D
Author:  Ron Parker [ Tue Jul 10, 2007 5:46 pm ]
Post subject: 
For what it is worth you can not compare a street app to a drag app. But my transmission builder which builds Dale Rose An Norm Foster also recondmends dextron fluid. None of us has had a trans failure in over five years. I could run royal purple or b&m fluid but he says run dextron in our cars. Thanks Ron Parker :D








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