904 ???

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joeboy

joeboy

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I am just doing a little thinking, and research, about which auto trans to run, and am looking for input. I have currently a 727 with a awesome shift kit, but it has not been in a car for 5-6 yrs, so may need to be freshened...

I have also heard many guys sayin' that a 904 will do the same job, and save some weight/take less power to run... I got a bone stock one of those, that would need the works.... Would I feel a performance gain with the 904?

Lastly, and my big question, I am kicking around running a "lock-up" 904 to keep the revs down an a longer cruise. Does anybody have experience with these transmissions in a performance application, can you get stall converters, and would it be worth it to find/rebuild one?

I would like the extra drop in RPM, but dont wanna modify the floorpan/trans stuff for the OD stuff...

Thanks in advance,

JOE
 
Joe the 904 will take a lot of abuse so for anything 425 hp and under you can use one with just a good Trans-go kit installed. Over that HP level you should do some upgrades IMO. As far as any perf. gain, it will be some but minimal. Probably get a little better fuel mileage too but it too would be a minimal gain. I have no experience with lock up units but I know converter selection is pretty limited. If you really want to get the best bang for your buck find a 998/999 (same physical size as a 904) with the low gear set that way you can run taller rearend gears and with the lower 1st and 2nd gear of the trans. it'll still perform good on takeoff.
 
fishy68,

thanks for the info. I really appreciate it. I may have to pick your brain when I start a rebuild, never done one myself...

BTW is the 998/999 a lock-up, or just a lower gear set?

What do you think of the 5.0 kickdown lever???




Any other thoughts or experience with the lock-up converters out there?

JOE
 
joeboy said:
fishy68,

thanks for the info. I really appreciate it. I may have to pick your brain when I start a rebuild, never done one myself...

BTW is the 998/999 a lock-up, or just a lower gear set?

What do you think of the 5.0 kickdown lever???




Any other thoughts or experience with the lock-up converters out there?

JOE
Click to expand...

Glad to help when I can Joe.

I believe both the 998/999 series have the lower gearset and one was lock up and one was non lock up but I haven't had a bunch of experience with them so you might want to verify that elsewhere. 99% of the torqueflites I've done are 727's.

Something I do know. Never use a 5.0 lever on any trans. that doesn't have the Hemi front drum and wide band. The 5.0 lever was needed to compress the stiffer wide band. It will almost always cause overlap when used with a standard narrow band. The 4.2 is the most you want to run and if you run a manual valve body most valve body mfg's recommend the 3.8 lever.

Sorry but I don't have much experience with lock up's.
 
personaly ive had a 727 in my duster and that thing blew apart first burnout tried on it upgraded to a 727 tf out of a cop car way better.

now i have a 904 and it is way better then a 727 i think i have a mild shift kit in it b&m star console and a 700-2500 stall converter runs great on street but i think the tc would be better if it was lower stall but way better in my opion.
 
OK, just a few points of clarification.

The 904 was the /6 trans, most had 3 rear clutches and 3 front clutch discs, the 998 came behind 318's, has 4 rear discs and 4 front discs. The 999 came behind 360's and had 4 rear discs and 5 front discs. You may find the odd 999 behind a 4 barrel 318 so it's not set in stone.

The low gear set came around sometime in the 80's, I can't remember exactly when but you could find it after that in any of the varients.

Lock ups started around 73 and up until about 76 it could be either one or the other, after that almost every trans was a lockup trans in a passenger car, trucks are a different story and depending on the package it may have been either or again.

Confusing I know, but prior to 72 you weren't going to find an A999. In 73 the reaction shaft, input shaft and front clutch drum changed to accomodate the 5 disc front clutch and non lock up input shafts for the late two ring input shaft can be hard to come by. You can however convert a 4 disc front clutch to a 5 disc, I think TCI sells the pressure and reaction plate you need to make the conversion.

BTW I've been running my 904 in the Duster and now the Scamp for 12 years now with a Turbo Action tranz brake. I don't use the brake all the time but when I do I don't use a two step, it's on the converter. I've never had a problem with the trans, even using the 5.0 lever (they are just easier to get) but I did crack a converter hub once.

I run Amsoil ATF and you can still read the ink on my clutches and bands. And no, there isn't any thing at all special in my trans, pretty much just stock stuff. I don't use a trans cooler either but my car is strictly a race car.
 
Thanks for clarifying things GJ. I have looked all over the net and can't seem to come up with any hard evidence of what the actual difference is between the 3 variations of the 904. One interesting thing I did find was on Allpar it said the 998 is 904 internals built in a 727 case. Not sure how they could do that without some major mods because as you know the pump is much bigger in a 727. I just wrote it off as incorrect info as I have torn apart a ton of torqueflites and never seen a 727 case with 904 internals. I know racers have done it (put 904 internals in a 727 case) but I've never seen it from the factory. If you know of any reliable website defining the differences please share it as I'd like to learn more about the little trans.

Oh and about the 5.0 lever. I have seen them work correctly even without the wide Hemi band and drum but it seems harder to get things properly timed. I never have a problem with overlap using the 4.2 lever and they seem to shift about as good as possible. That's why I don't recommend the 5.0 lever.
 
I don't know of any website with the info, it's just cumulative knowledge from 35 years as a Chrysler tech. Some stuff is just bound to rub off on you. lol

You're right though that Allpar info is bogus.

I'd run a 4.2 lever, just don't have a good source for them and the 5.0 are easy to get. I just back off the band adjustment a little.
 
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