999 clutch pack in a 904' & opinions on fluid

[RogerRamRod]

I've read where people say to put 5 discs in the forward clutch as opposed to the 4 that I have now, but never see part numbers and details. I've recently read that the A999 trans is the 5 disc version of the 904. Do I simply order clutch parts for the 999?
Are the 5 frictions and steels thinner, or are there different pressure plates as well? Any actual part numbers? What else will be needed to make this work?

2nd subject; fluid. Having a Chrysler Torqueflite, I would be inclined to use ATF+4 fluid. Somewhere I read that aftermarket frictions (Alto Red Eagle)are designed with Dexron in mind. I have a L\U Torque Converter made for a Chrysler. Will Dexron fluid cause converter shudder, and\or will ATF+4 cause clutch problems?

 

[RustyRatRod]

I would use Dexron II just to keep it simple. Also, the WIT Transmission site is a great place to get parts.

WIT

 

[Duster346]

A 999 is a lockup 904 with a rigid wide 2nd gear band, 5 disc high gear drum, lockup pump, and lockup input shaft. So the answer is, no, you cannot put lockup 999 parts in a non lockup 904.

You can however put the 2.74 low gear set from a 998/999 into your 904 if you take the front planetary and sunshell/gear assembly.

I cannot stress this enough regarding 904s--you can get in real trouble really easy by mixing and matching parts. The best thing to do is grab a complete core off the shelf and build it. The easiest way to get 5 high gear clutches is to install five .061" grooved red clutches and five .068" steel plates into your 4 disc 904 high gear drum. Selective snap rings are available to obtain the proper clutch clearance, and you can machine the apply piston in a lathe if needed (I do not recommend machining a step in the pressure plate, and I have never recommended that).

 

[mopowers]

A 999 is a lockup 904 with a rigid wide 2nd gear band, 5 disc high gear drum, lockup pump, and lockup input shaft. So the answer is, no, you cannot put lockup 999 parts in a non lockup 904.

You can however put the 2.74 low gear set from a 998/999 into your 904 if you take the front planetary and sunshell/gear assembly.

I cannot stress this enough regarding 904s--you can get in real trouble really easy by mixing and matching parts. The best thing to do is grab a complete core off the shelf and build it. The easiest way to get 5 high gear clutches is to install five .061" grooved red clutches and five .068" steel plates into your 4 disc 904 high gear drum. Selective snap rings are available to obtain the proper clutch clearance, and you can machine the apply piston in a lathe if needed (I do not recommend machining a step in the pressure plate, and I have never recommended that).

That's great info. Thank you!

Probably a stupid question, but why don't you recommend machining the pressure plate? I see some trans shops offering thinned/machined 727 pressure plates. Or is it only a 904 thing?

 

[408 swinger]

Cope and A&A have thin plates allowing you to put 5 discs in your 4 disc drum.

 

[RogerRamRod]

A 999 is a lockup 904 with a rigid wide 2nd gear band, 5 disc high gear drum, lockup pump, and lockup input shaft. So the answer is, no, you cannot put lockup 999 parts in a non lockup 904.

You can however put the 2.74 low gear set from a 998/999 into your 904 if you take the front planetary and sunshell/gear assembly.

I cannot stress this enough regarding 904s--you can get in real trouble really easy by mixing and matching parts. The best thing to do is grab a complete core off the shelf and build it. The easiest way to get 5 high gear clutches is to install five .061" grooved red clutches and five .068" steel plates into your 4 disc 904 high gear drum. Selective snap rings are available to obtain the proper clutch clearance, and you can machine the apply piston in a lathe if needed (I do not recommend machining a step in the pressure plate, and I have never recommended that).in

Thank you for the info, that's the kind of help I was looking for.

 

[Duster346]

That's great info. Thank you!

Probably a stupid question, but why don't you recommend machining the pressure plate? I see some trans shops offering thinned/machined 727 pressure plates. Or is it only a 904 thing?

We offer machined pressure plates to thinner thicknesses, but not stepped. I've removed several broken stepped pressure plates.
We offer this mainly for the 727 and RE/RH transmissions when installing more than 6 friction discs. I am more inclined to use a thinner snap ring or machine the apply piston a small amount on the 904.

 

[Duster346]

2nd subject; fluid. Having a Chrysler Torqueflite, I would be inclined to use ATF+4 fluid. Somewhere I read that aftermarket frictions (Alto Red Eagle)are designed with Dexron in mind. I have a L\U Torque Converter made for a Chrysler. Will Dexron fluid cause converter shudder, and\or will ATF+4 cause clutch problems?

Modern friction materials can run in any fluid without issue. I would not poor ATF+4 into a 50+ year old transmission that has never been rebuilt.
The standard fluid we use is DexIII on a basic, mild street strip build.

 

[junkyardhero]

We offer machined pressure plates to thinner thicknesses, but not stepped. I've removed several broken stepped pressure plates.
We offer this mainly for the 727 and RE/RH transmissions when installing more than 6 friction discs. I am more inclined to use a thinner snap ring or machine the apply piston a small amount on the 904.

does the 42RE/RH follow the same rules of don't be mixing and matching bits around as the earlier stuff?

 

[Duster346]

Not so much with the 42/44 stuff as that will all interchange with each other, although I do believe the 42 may have had 3 pinion planetaries front and rear, so no reason to go from 4 pinion to 3.

The 1-3 portion of the 42/44 trans is all very similar to the 999 but the majority of the parts will not interchange with a 904, 998 or 999. The later model 4 speed used a bigger high gear drum with two bushings, a larger diameter sun shell, and specific input and pump. The few parts that will interchange with a 904/998/999 are the front and rear planetary, ring gears and sun gear.

To my knowledge and based on what I've torn down in the past, the 998/999 all had the 2.74/1.54/1.00 four pinion steel planetary gear train, and the same holds true for the 44.