Ive been emailing Curt at the Gear Vendor. I thought about doing the TH 400 with the GV for final drive of .78 . After thinking about it, I realized I could do the 700R4 with GV OD, and have a final drive of .55! Wow.. As an extreme example, that means that I could run 4:11 gears at the light, and still run at 70mph at 1728 rpm! Can a 700R4 work without computer controls? What input does the tranny need to work properly. I think I just have a vaccuum line going to mine.. Not sure. but its a th350, Talk about the best of both worlds. and I think.. im not sure of hte math here but, I think the GV reduces the RPM by 22%, so If you have 4.11 gears and turn the OD on, it would be like having 3.20 gears... turn it offf and you have super low 4.11 if you want. Leave OD on and you have 3.2 gears, plus the .7 700 R4 and you got real high gears for highway cruising. Gentlement, this is what i am going to do... as long as the 700 will work without a computer, everything should be fine.
If you change trans or add a gear vendors go to a 200R which does not have the attendant electronics. When people do this type of change usually they go to something like a 3.73 rear gear. I assume that you have a 8.5 corporate rear and not a 9 3/8. If you have a 9 3/8 it is hard to finf anything better tha a 3.42.
It would also give you an eight speed! I do not think it is worth it. Run a well built 200 and a 3:73, it is perfect for Buicks. If you try to run any cam at all you will be too low in the powerband.
how does the tranny know when to shift? Is it possible to have it shift manually? While final drive would be too low in the powerband wouldnt shifting into 3rd or shifting out of overdrive put you right back into the optimal powerband? So has anyone on here done the 200 or 700 with GV?
700r4's work off a Throttle Valve cable so you don't need the vacuum modulator like your 350th and 400th trannies. Precise adjustment of them is critical to their operation. I'm assuming your running a Buick engine, your post doesn't say, but the 700R4 only has a Chevy bell housing pattern. The t200r4 has a dual pattern and will bolt directly to your Buick engine. The gears in the 200R4 are also space closer together which means it doesn't have the really deep first gear of the 700R4 but it has a lower 4th gear -.67. You could run a 3.90 rear end and still have about the same final drive as you would with the 700R4 and the 3.73 gears. Sounds like a good time.
http://www.oldengine.org/unfaq/leadfoot/trans.htm Here it says that some trannys actually use up a certain amount of horsepower. A TH350 uses 30 a 700R4 uses up 70! Anybody know abou tthis?
All rotational mass does. All trans do. All wheels do. All rears and driveshafts too. Yout present TH 400 does and likely more the the TH 350.
I have a 200-4R trans in my car with a 3.73 rearend. It's perfect. 2100 rpm's at 70 mph down the highway with a 28" tall tire.
The problem he has is I suspect his rear gears are 9 3/8s since he says his trans is a 400. The lack of replacement gear sets fro his rear makes his only choice a gear vendors.
I have a chebby truck with a 700r4. It was just overhauled for $1500. Not to cheap to me. But at 65mph I am turning 1200rpm wich is basically idling down freeway. Don't know what rear gears I have, didn't give it much thought to check it. But it does have the cable to the carb and has to be adjusted right or can cause early failure of tranny. And it does tend to upshift and downshift between 3rd and 4th a lot at part throttle. Fixed it with a B&M part that won't allow no up and down shifting till your 3/4 of the way into pedal.
Don't forget that there is a limit to how low you can go without hurting your gas mileage. You will reach a point where you are lugging the engine. I have a 2.56 rearend, and I could see going as low as a 2.29 (whether that is your rearend ratio or accomplished with an OD). But any lower than that and you're gonna be too low IMO. A great benefit of those transmissions is the lockup convertor - those help increase efficiency. If you are gonna have an OD, I would go with a 3.42 or 3.23 or something, which will give you a nice highway RPM with the lockup. -BC
I you are dead set on getting a 700r4 try looking here: http://www.transmissioncenter.net/highperflist.htm They even sell the BOP adapter plates.
Interesting, what would be the best RPM at 65mph for optimal gas mileage in a 350 4bbl, that is built for low end torque? and whats better the 200R4 or 700R4? Do both have the lockup converter and can both be run without any computer controls? Which is stronger or can be made strong? Would they be as strong as the stock TH400? I have the TH 350 now, and stock rear end. I dont know what it is though, probly 3.08 open but im not sure.
You likely have a 3.08. A TH 400 stock has the biggest shafts etc. They were designed for big torques engine and 700R s and 200Rs were not as much. But they can be made stronger if you spend the $$$. My advice is for you to save your money because the conversion will be at least $2500. You would have to do a lot of driving over a long period with much of it on the road to make up for the up front conversion cost. Oddswise you will not have this car as a primary driver for very long. If your focus is gas mileage and cost savings you have the wrong era car. If you want performance in that heavy of a car you need to put in a 455 which is going to add additional cost and get even worse mileage. Even if you did performance will still be limited by the weight of this model. For best resale leave it as a stock 350 2 barrel.
are you saying that a conversion to 200R4 would be 2500? or the GV unit? If you mean the 200R4, where would the cost come from? I havent priced them but whole cars with 200R4s can be had for a few hundred dollars, how much is to have have one rebuilt? As far as reselling it, what do you think it could be sold for as is? The pics are in the members rides section. Thanks for your input. Oh and what 70mph RPM would be optimal for economy on a 350 built for torque?
I think a turn key GV is about $2500 and you may have to change your driveshaft, move the cross member and change your rear gears for the 200R. If you get one built for a lot of torque that alone could be more than $2500. Then there is labor, cv joints, etc. So yes if you farm it out with a newly rebuilt unit I could see $2500 there too. As always if you have the skill to do everything yourself you can always save money.
Gary, I did the 200r4 swap on my '66 to replace the 2 speed ST-300 and I'm into it for about $1200. I did all the work myself and used a BRF code trans from an '87 GN which was $500 alone. You can pick up a junk yard trans for $50 all day long from Pick-a-Part or places like that, and it might be fine behind a mild or stock 350. You would be pushing your luck running a stock 200r4 behind a 455. Expect to pay $2-3k for a well built 200r4 from CK Performance or CPT in Cali. Do a search in the trans forum and you will find all kinds of info. Brian
