OK I have a 998 with the low gears but it also has a very good non-locking 998 spline converter that footbrakes right at 3100 behind the 341" LA motor in the Rocky. I also have a good rebuildable 904 core I just picked up last night and a T/A shift kit....(I don't want to put a full race VB in this thing just yet....not until I get a handle on how this 85" wheelbase toy goes down the track.....with the stock 318 it went straight as a string, but now I'm doubling the hp and the launch RPM speed.

Since i already have a good (great) converter, The main achilles heel (I'm told) of the 998 is really the high gear spring pack is too weak and tends to slip in high gear for racing....but I'm also told this could simply be swapped for a 904 drum/spring pack and would work well for a maybe 450 horse 2800 pound "thing" with 4.56 gears.

The other option is obvious....swap the low gear set into the 904 but that leaves me with the dillema of finding another ($$$) converter to replace the one that happens to work very well.

Based on what I've laid-out and given the motor car we're dealing with, what is the best use of the components I have? I'm Thinking both the Low gearset and the 998 input shaft/vert can be swapped into a 904 (which would really be perfect) but I may be off base.....

I just want to build it with the best combo of parts that I have on hand and go rounds reliably....to be honest I probably don't NEED the deep gearset with this car but since I already have them...

I've built several trannies but I've never really stayed up on the 'what goes with what' parts combinations that are possible.....I know some of you guys know TF trannies inside and out, so I'm all ears

I'd love to ship it off to one of our Moparts guys on the site here...but the Varners (Bill Sr. and Junior) here in Charlotte are very well-known/respected as a TF gurus and a long time (3 generations) racing family....and I haven't blown up anything he's built for me in over 20 years I've known him.....and that's been quite a few Torqueflights

I know the varners real well they will do you a good job. If you want give me a call and I can tell what will work? I have run a 904 with low gear set for about 13 years in 3100 lbs car that runs mid to high 9 in quarter. It will live!!! My number is 803 518-5495

Beware of mixing and matching 904 parts. There are way more subtle variations than a 727. Find Dizusters archive post for more info. Correctly done they work great,mismatched they can be your worst nightmare. It took us a year to figure one out.
Doug

dvw,

Thanks and that's EXACTLY why I"m posting up....I talked to Johnny and basically If I can swap the 998 input shaft (so i can reuse the same non lock-up converter) and gears into the 904 I'm good. Johnny did recommend going to the 727 style high gear spring pack which will be a great upgrade, especially if I wind up spraying this thing someday.

I'm pretty saavy on the stuff on the front side of the flexplate but I'm not afraid to ask what I don't know enough about.

The easiest thing to do would be just build the 904 and get a new vert but like i said this vert and low first gear work so well I'd hate to change anything about it.

Quote:

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The main achilles heel (I'm told) of the 998 is really the high gear spring pack is too weak and tends to slip in high gear for racing....

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The hydraulic application of the piston locks the clutch pack up.....not the spring.

The spring is there to release it when not in reverse or high gear.

The problem with the single coil spring presents itself in 1st gear
at high RPM. The spring unwinds itself and loads the high gear piston,
which subsequently burns up the clutches. A kit from A&A replaces the
single spring with a multi-spring return much like the 727s.

It also provides a cleaner release if using a trans-brake.

As mentioned, depending on years there are MANY different issues you could run into.

What's the problem with just using the 998 you have?

By the way, the high gear spring in the drum is NOT the application spring. The application of the clutch is still done by pressure. The Spring is actually there to turn the clutch off. At very high RPM the spring can unwind. But we're talking pretty high RPM. I ran a 340 duster to ~7200 on a regular basis with a stock drum spring, and it never showed any signs of problems.

If the 998 is a 4-clutch high gear drum, I don't see any reason not to just use the 998 as is. The 904 doesn't have anything special in the high gear drum spring.

Whoops, ST/ beat me to it!

By the way, the input shaft splines are not any different between the two converters. However depending on the year of the 998, it might have a different Pump snout drive...

The input shaft has to go with the pump (depends on the # of sealing rings) The pump MAY have to go with the high gear drum (depending on clearance to the pump, and large diameter sealing ring differences), the high gear drum MAY need to go with the sun shell (two different diameters), etc...

Be very careful.

I know when I got the converter, the 998 has 1 more (or 1 less...I Can't remember) spline on the snout.

So is there anything else internally in the 998 that would prevent it from performing the same as the 904? What else is different?

The non locking/lock-up splined Vert is the main reason I want to keep the snout in whichever trans, It's a 9 1/2" unit that hooks really sweet.

Yeah, that's a much better explanation of the Spring pack Makes more sense now.

I just want to go rounds and not blow it up.

The input shafts are the same spline. The difference is that a 998 lock up/non-lock up has an extra steel sealing ring. It only impacts the pump, not the converter.

I have a 999 3 ring input shaft that was run with a 904 converter I my garage right now...

The only thing you might want to look at is how many clutches the 998 is that you have. If it was a V8 trans to start with, it probably has 4, but if it only has 3 for some reason, you might want to upgrade...