Building a 700r4 for autox?

I may be getting a free 700r4 soon. Eventually I'm planning on a 383 for the Vette...figure 500hp/500 ft/lbs of torque or less. 

• What does a 700r4 need done to it to handle that much power/torque? 
• What improvements can/should be made for shift response?
• Do I want a manual valve body? 
• What else do I need to know?

I see a lot of info relating to drag racing but I'm not sure how much is applicable to autox. I don't really want "hard" shifts that could upset the chassis, just predictable ones. Likewise, I'm not doing any drag launches, so I don't need a high-stall converter. 

When I looked into this for a 5.3 swapped RX-7, I decided the 200-4R would be a better choice.  Easier to find reverse valve bodies, gear ratios are a bit better (less drop between gears).  I wouldn't have turned down a free 700-R4 though.  I have seen them live behind moderate big blocks although this is street use and not competition.

A manual valve body will make shifts instant, when you want, and generally harsh enough that you will still have to play games with the throttle when shifting to keep from upsetting the chassis.  (They eliminate the TV cable altogether and run max line pressure all the time)  When I had one in my Ford, I got the hang of rev matching the downshifts fairly easily, and lifting a little before shifting up is no problem either.

Converter stall speed is relative to where your engine's torque peak is, irrespective of what you are doing with the car.   That said, if you have a loose converter and you upshift to below the stall speed, you end up with a much less harsh shift.

If you go manual, a good shifter is key.  I prefer the ratcheting type, and ratchet shifters that have detents for all four gear positions are few.  I did see one of those goofy Cheetah shifters in an autocross C4 once that seemed to work out okay for the owner, but I could barely work that thing on the street.   Plus it was a forward valve body, which I am really not a fan of.

Oh yeah - if you go with a manual valve body, make sure it has engine braking in 1st.  Not all of them do.

In reply to Pete Gossett :

To answer your questions in order with my opinions.... 

1.-Yes. A lot of improvements. More in a bit on this....

2.-Again, lots.

3.-You don't specifically need to, but....

4.-Expect to do this many times over until a "miracle" happens.

Now, to expand on what I was saying...

One of the biggest shortfalls to the 700/4L60 is lube. I have seen WAY too many planetaries burnt up because the factory never provided enough oil to them, that's on top of not enough gears to handle torque loads. you can upgrade to the 5 pinion planets and like, but IMO, you be better off dropping the coin, about $1400, on the aftermarket planetaries that drop the first gear ratio from 3.06 to 2.84(?). Plus the gear drop from 1st to second isn't so horrible.

Shift kit. Find one and use it.

You don't have to, but you have to watch what the full throttle shift rpm kicks in at based on the governor.

Personally, it seems like 3-4 "tries" at making 700's work in various forms is the give up point to when people either forgo OD or find a 4L80. 

Even for free, I'd start with  4L60e. You can easily either tune the TCM for shift quality or "pin" the PCS and manually shifting the electronic valvebody with plain switches. That way you don't have to shift but once, since you have locked out all the other gears.

Ranger50 said:IMO, you be better off dropping the coin, about $1400, on the aftermarket planetaries that drop the first gear ratio from 3.06 to 2.84(?). Plus the gear drop from 1st to second isn't so horrible.

AKA, "run a 200-4R"... 

It'd be nice if GM had a 2.48/1.48/1,0 overdrive trans that wasn't as massively overbuilt and heavy as the 4L80, and was fully hydraulic so you didn't have to deal with the solenoid lag like electonically shifting always suffers from...

Knurled. said: AKA, "run a 200-4R"... 

And find me one, but the metric 200's are stamped steel crap you have to weld together to take any power. BTDT. Those damn things failed at the same rate as 700's behind the same damn powerplants.... 

Thanks guys! A couple more points:

• I saw a shift kit posted here that still worked like an automatic in 4th, but manually in 1-3. Since it will always be a street car, it really has me interested. 
• One good thing is 1st & 2nd seem geared perfect for autox now. I'm sure I may find courses occasionally where I need 3rd, but I haven't yet. 

Are the 700r4 and 200r4 tailshaft housings interchangeable? The C4 has a unique design, but fortunately I have a spare. 

In reply to Knurled. :

I'm not sure I want/need engine braking? It seems like it would be easier to be smooth without it. 

200/700 tailshafts are not interchangeable because the 200's are still part fo the main case and don't unbolt.

In reply to Pete Gossett :

Easier when coming off power, maybe, but it will shock the tires Everytime you get back on the throttle.  Would you dip the clutch into every corner in a stick car?

Engine braking can be managed pretty easily with an auto.  Make sure you've got a loose enough torque converter and stay in a higher gear (relying more on the converter for acceleration) if the lower gears are giving too much engine braking.  That'll give a bigger difference between on-throttle and off-throttle RPM, so less engine braking for similar effective gearing (and ability to put down power). 

In reply to rslifkin :

Interesting, I hadn't considered utilizing the torque converter like that. 

In reply to Pete Gossett :

I tend to do it in rallycross (run with the shifter in 2 so it leaves the line in first, grabs 2nd and then unless I go WOT at low speed, it'll stay in 2nd).  Makes a big difference in how hard it'll bite with oversteer if I lift, but in that situation at least, it doesn't compromise acceleration at all (as I've still got more power than I can actually use). 

In reply to rslifkin :

This method worked best for me in autocross as well. Really helped keep the chassis tight and control weight transfer. 

In reply to rslifkin :

Interesting. Granted, I've only done a total of 4 autox runs in it, but at the Challenge, leaving it it 1st allowed it to rocket out of corners until I reached a point I needed to upshift. 

Knurled. said:

 

A manual valve body will make shifts instant, when you want, and generally harsh enough that you will still have to play games with the throttle when shifting to keep from upsetting the chassis.  (They eliminate the TV cable altogether and run max line pressure all the time)  When I had one in my Ford, I got the hang of rev matching the downshifts fairly easily, and lifting a little before shifting up is no problem either.

I want to say ive seen vacuum modulated manual valve bodies that control the line pressure based on vacuum so that shift firmness is based on throttle input and load. might be a little more forgiving.

I like a 200r4 because the  First Gear is more useful,  A gearset of 3.42 - 3.50's Gets you out of First and to the sweet spot in an Auto

How often would you actually shift in autocross?  My redneck calculations say that Pinto Bean will probably stay in it's 1.48 second gear the whole run.