I have a 700R4 (duh) and 3.23s. Right now, my cut off is about the time that the trans is ready to shift from 3-4. However, I am planning to get a cam for it and a tune, so I am deleting the cut-off. I know that there is something in the trans that won't allow the car to run in 4th at over 2/3s throttle. What is it, and how do I get rid of it?

I also plan on installing a T56 within a few months, so should I just let it be?

 

Since you're going to change to manual, you might as well have some fun with the auto before you pull it.
The reason that the 4th gear is "unavailable" above half throttle is the overdrive section won't handle more than 150 hp or so.
With the stock engine and stock gears, the factory figured that the car wouldn't go that much faster in 4th anyway so why bother spending money on a robust OD section.
http://www.jegs.com/webapp/wcs/store...chItemId=83037
For $59 you can move the 3-4 shift point from 50% to 85% throttle.
Here's what the "transmissionhead.com" gurus have to say about it:
#20. 700R4 full throttle 3-4 up-shift sleeve. Now you can have a full throttle 3-4 shift. At 80 MPH it takes 90% throttle to make a 4-3 downshift. Can be installed without removing the valve body. The Up-shift Sleeve also eliminates part throttle 4-3 downshift for less gear searching. This is an extra option on the 700 Raptor. Not recommended for motors over 250 horse power. Cost $58.00
Have fun!

 

So, that means that if I have the pedal at less than 85%, it will keep acelerating through 4th gear, instead of jumping back into 3rd? And at more than 80 mph, I would pretty much have to floor it to make it go into 3rd? That sounds pretty cool.
Where does that go? I mean, would have to drvop the trans to change it?

 

Right. It moves the "forced downshift" point from about 1/2 throttle to above 3/4 throttle. You won't have to drop the tranny, but you will probably have to drop the control valve to change it. Read up about the check ***** and where they go and have some "trans-jell" to hold them in place before you drop the control valve. The TV plunger valve is at the end of the TV cable lever in the valve body. If your engine is still stock the 4th clutch may carry the torque at 80% throttle enough to get video of the speedo at 140 mph...
The aftermarket TV plunger is primarily for low hp engines that don't make enough hp for towing in 4th below 1/2 throttle like the POS V6 in my pickup.

 

Add the "modified" Trans-Go Performance Shift kit, this will help the WOT 3-4 shift to live much longer. The TV plunger sleeve has two 4-3 part throttle holes that can be blocked using two allen screws. This will eliminate the 4-3 downshift at high speeds, and will allow 3-4 WOT shifts in the majority of cases. This can be done when the Shift kit is installed. By the way when you modify the 4th gear feed circuit, you help the WOT 3-4 shift. You are not putting any undue stress on the unit. I have never seen a 700R4 or a 4L60E give way on a 3-4 WOT shift. The most that can happen is to burn the 2-4 band. If this were a problem, then Trans-Go would not block the 4th gear accumulator, and use a .187 - .203 size feed hole.

 

You don't have to drop the valve body to install the downshift sleeve. I bought a B&M one years ago and installed it. It eliminated the annoying gear hunting between 3rd and 4th all the time. All you have to do to install it is drop the pan, and you'll be able to see the plunger and sleeve assy. It comes with instructions.

 

What all is in this kit? Is it a "manual" kit? I need your help on another problem when you get time...

 

A corvette/9C1/Van TV sleeve and plunger will eliminate part throttle kickdowns under about 100 mph, unless you stomp it to WOT. My stock van transmission as well as the 1992 replacement, both shift 3-4 @ WOT, just they have to get up to about 5,200-5,500 rpm(4,200 before I changed the governor) before they will.

 

If I can pull around 120-125 at the top of 3rd, what can I expect if I can keep it in 4th? I've heard stock L03s with my gear setup going 130-145. With an LT1 cam, good exhaust, and some intake mods, could I do 150? I have the tires for it. Z Ws... hehe 186. Yea, right.

 

I think it'll be close to 140. Be sure to have a long straight stretch of road.
Heck, here's one for that will give you 3/4 throttle for $33.99 .
http://www.jegs.com/webapp/wcs/store...chItemId=31935
Stick one in and let us know!!!

 

Yeah, that's the same part I put in mine a few years ago. Easy install and works great!

 

Alright I'm confused will the b and M unit let you keep the pedal floored and accelerate through all the gears? Then it will hold 4th at WOT? And If the OD section of the tranny only holds 150 hp wouldn't the tranny blow in 4th gear all the time since 350 tpi have 230hp and Lt1's even more?

 

This is the description of the B&M part:
"TH-700 transmissions will downshift from fourth to third gear anytime there is more than half throttle (except Corvette and some Camaros and Firebirds). So it’s impossible to cruise at high speeds in overdrive (fourth). This prevents a forced part throttle kickdown from fourth to third gear, and allows cruising at higher speeds in over-drive. The transmission will only kick down from Fourth to third at 3/4 throttle."
So the answer to your questions are:
"keep the pedal floored and accelerate through all the gears?" No.
"Then it will hold 4th at WOT?" No.
"wouldn't the tranny blow in 4th gear all the time since 350 tpi have 230hp and Lt1's even more" No. The transmission will never be in 4th gear above 3/4 throttle and will never see full horsepower in 4th.
In a nutshell: stock trans is in 4th only at 1/2 throttle and below. With the B&M kit, trans is in 4th at 3/4 throttle and below. 230 hp X 75%=172hp.
The newer Fbodies-LT1 etc, use electronic shifting transmissions not 700R4.
Pro-built's kit beefs up the 3-4 pressure to handle the extra power.

 

I put the valve in mine because it kept "hunting" for the right gear. In other words, it'd shift back and forth rapidly between 3rd and 4th a lot. Changing the shift point to 3/4 throttle from 1/2 throttle completely cured this annoyance on my trans.