i need to build my tranny to hold 400hp and be dependable, from what i under stand its a must to have a .500 boost valve and billet servos and alto clutches, i was wondering is there any other major week points beside the sunshell gear and the 3-4 clutch pack, will a stock pump hold up?

 

Go to www.700r4l60e.com this will give you everything you need to do this right. If you have any questions on this let me know?

 

The 700r4 transmissions "weakness" is primarily a problem of building pressure and maintaining it. I have run very hard with a 400hp setup and a "basically stock" 700r4 for years. I ran a stock 7 vane pump (older style, the 10 vane newer style is better). I ran the cheapie clutches, and a "reconfigured" stock servo. This trans did get a transgo shift kit. It ran very well, shifted hard enough to squak the tires going into 3rd at 70MPH. All I can say is have a very reputable shop do the kit installation, that is critical. The primary problem with these transmissions is building enough pressure and maintaining it. These tranny's tend to bleed off pressure internally through leaks at various seal points, and very occasionally a result of a bad casting. Fix the leaks, and you will be rewarded with a remarkably tough trans. This lack of pressure allows the clutches to slip or the 2nd apply (2-4) band to slip. Of course the slipping (a failure in itself) causes transmission failure quickly. I ran this tranny very hard including many, many 1/4 mile races, bumper to bumper traffic, aggressive throttle application was the norm for this trans. As a note, this ran with no tranny cooler (just the stock radiator cooler) and a 2800rpm stall lockup converter. After 130,000 tortured kilometers the trans lost pressure and the pump failed. After disassembly, the reason the trans failed was a busted ring which holds the pump vanes out. It has since come to my attention that there is an aftermarket set of "unbreakable" rings available for not much cost. My advice: put them rings in no matter what else you decide to do to the trans.

Also, my current engine build is aimed at 600hp and 510ftlb, which will be travelling through a very similar trans, but with the "unbreakable" rings added of course. I do have a 0.500 boost valve in this one too. We will see how long this one lives, as it will see regular track duty, and commuting just as the last one did.

I only state what I have learned from experience. It will take someone very experienced with the 700r4's to recognize and repair all the common pressure loss areas, and even then leaks that are a result of a poor casting (case) may go unnoticed.

If you will be running slicks, and a high stall (3000+rpm) then I'd upgrade with a good sunshell, good clutches(+band), a 0.500 boost valve, and a good servo. I know the transgo shiftkits properly installed go a long way on their own. If you will be running serious power (nitrous) and/or really low rear gears you should also consider upgrading your sprag and planetary gearsets.

I am attaching a expanded view picture of the main mechanical components of the 700r4 for reference.