700 R4 with Gear Vendor Overdrive

I haven't put enough miles on the car to figure out the mileage yet. I'm still working out a few bugs also and the car will be getting the 3.90 posi soon. My main goal was not mileage, but increased performance and drivability. The 3.90 gear gives me the performance, as does the gearing in the transmission itself, as the ST-300 basically has no 1st gear. It was like starting out in 2nd gear and the car was a real pig off the line. Now the car launches nice and does good long smokey burnouts, even with the current 2.78 gear.

The BRF code is used by the '87 Grand National and is the performance version of the 200r4. It has a special valve body and governor with higher shift points then the other 200r4 out of Caddy's and station wagons, etc. My WOT shifts are at about 5500 RPM, where others codes are usually around 4000 rpm.

Good luck!

Brian

 

Well, I for one think a double OD is ridiculous. that being said, I have some input here regardless. first 700R4s are braindead. all of them. the 4L60E thats the computer version of the 700. I am not a fan the 700, the gear spread is better suited for a truck.

next, my brother had a similar setup. a T56, the six speed found in 93 and newer F-cars and vettes, has 2 ODs. 5th is .7something and 6th is .50 :eek2:. his car was a 86 trans am, 3.23 gears with very short tires. 6th was useless. plain and simple, not worth having. it was a very torquey 400 chevy, but it would never see more that 1400 rpm ant 75 or so. even then, it chugged. the mileage was nothing to sneeze at compared to running in 5th. about the same actually.

lastly, you'll really need EFI to run that low of an engine speed effectively.

 

Thanks for the input! I appreciate your insight and experiences!, so at 1400rpm at that speed, there simply isnt enough power to be efficient? I thought for sure the gas mileage would be much greater at lower rpms. i figured less RPMs = less air fuel mixture but I guess it must have more to do with throttle position.

 

for the cash your talking you could have a 4l80 and computer controller and it would take as much power as a built 200 700uzzled:

a 700 wont live long behind a big engine

 

Thats true to a point, but your pushing the extreme. It takes alot of power to move a two and a half ton barge 70 miles an hour. figure in drag, hills, wind etc, and your motor is really working. at 1400 rpms, the motor isn't really going to have the grunt to do it, unless your really heavy on the gas. at 2k, less on the gas, same power... better mileage.

for me, ideally, 75 around 2200-2600 rpms. I'm around 3000 or so, which is annoying, but do able

 

Way back, I read a fuel economy article in an industry magizine. According to it, the best economy was achieved when the cruising MPH was matched to the engine's peak torque RPM. Which I believe is also the point, under light "cruising" load, at which the egine can maintain the highest average manifold vacuum level. And MAP is directly related to how high the primary rods are pulled out of the primary jet. That said, a stock sbb350 will probably achieve this around 2200 RPM. I think GM engineers were right on the money re. economy and highway cruising speeds vs RPM using 60's/'70's technology. (aside, my stock 72 Skylark 350-4, TH350, 2.56 would get 20-22MPG highway)
The 200r4 with a lock-up converter would be the easiest method. It has the same dimensions as the TH350, and uses the same driveshaft (confirm?). The BRF version has a 3rd and 4th gear switch which the ECM uses to decide when to automaticaly engage the lock-up solenoid, the rest just have the 4th gear sw. Minimally, all you would have to do is wire up a manual switch to the solenoid with an over-ride switch on the brake pedal.
Look to spend about $1700+ for a stout (400lb/ft) CKperformance or Brian Hoffer 200r4, + $250 - $700 for a new L/U converter. The main problem with the 200r4 is the lack of clutch surface area. The pros do their best to bandaid this with a wider band, extra clutches and some billet parts. Longevity in a heavy car may still be a problem, especially if your car is going to see track passes with sticky tires.
If your going to run it hard, I think your longest lasting, most fuel economical route may be a TH350/400 with lock-up or a switch pitch and the GV unit. Lock-up would be key, as stated before this would eliminate 2-300 wasted RPM.
.02's

 

Ive heard this before also, but I've heard nothing to convince me there is anything more to this than an old wives' tale. The airflow conditions (airspeed, pressure gradient, mass flow, etc.) are totally different at light throttle for MPG than for WOT torque.

If anyone can provide some good reasoning (or even a well-performed statistical analysis), I would love to hear some evidence!

In any case, I also believe that the engine won't get optimum MPG at 1400 RPM.

-Bob C.

 

I say SP400/GV is the way to go . I like the fact that you get a super tough tranny thats dirt cheap to buy and fix. Then the GV unit is bulletproof as well and will allow gear spliting if wanted/need. And to top it off the switch pitch!
You have a nice tight converter for driving around the street and highway but have high stall available for launching at the track or stoplight fun.

My second choice would be a 4l80E. The thing thats sucks is if you hurt it its big bucks to fix. The converters are expensive if you get a performance one.
Plus if you need a high stall say 3000.....you have to live with it around town until you get into overdrive on the highway. With the s/p you can cruise around in low stall and it drive like a stock converter.....jmho

 

My truck is a 4x4 but it has grunt with 33 by 12.50 tires. RV cam in her with tubular headers, 750 carb and ported heads with 350 motor. And she gets 16 mpg down highway. The 700r4 has been built and barks in 2nd gear. And have pulled my dads 1 ton diesel around when it broke down.

 

700/4l60/65 will give you good gas milage and has a really good gear set especially off the line

but a highly built one will only hold up to 600ft lbs of tq and the 200 is about the same

your chevy small block doubtfully makes this much but a 455 with a few mods will

a stock 4l80 will hold about 650-700 and built pretty much what ever you want to throw at it

if you want to have od and gobs of power an 80e is the only thing that will hold up as for as replacement parts all the od trannies internals cost about he same other than the od feature the 4l80 is essentailly a th400