Scenario: 2200 pound highboy coupe, 1970 sbc, two 390cfm carter carbs, rvtype cam, sprint car headers, stock internals, 3.70 butt gears in 9", 30" tall tires....I am thinking about using a 200-4r overdrive tranny vs. T-400 which is in the car right now. At 70 mph the rpms would be about 2900 with the T400 vs. 1900 with the 200-4r tranny. thats a lotta difference...using the same 3.70 rear gear. I can drive it sanely when I need to (takes the fun out of it somewhat, but ya gotta do what ya gotta do, man!) My wife and I plan to mostly use this car for weekend jaunts within the state (50-300 miles) and on an occasional once or twice a year road trip out of state, so will probably see mostly 60-70 mph on the open road...hence my question about mileage. Will this big drop in RPM be as big a gain in mileage to justify putting in the OD tranny? Or should I just go ahead and use the T-400 and switch out the 3.70 rear gear with a 3.00 set, which would drop the rpms at 70 mph from 2900 to 2350? I like the 1900 rpm better, but....? Looking for your advise so I can get to finishing this pile and get on with driving it....
With a mild rv cam the overdrive will make a difference. If you had a big cam it wouldn't make much more. Setting the carbs up will make a differnce too. Are you running a progressive linkage? It won't take much to pull the coupe down the road, and you don't look like you are going for all out performance. I'd use the overdrive. It'll be quieter, run cooler, less wear and tear. I used a 200r4 in a 1948 sedan delivery with a stock 350, and 3.40 gears. It was getting 20mpg + on the highway. It was a nice trans. Jeff
You could go with lower rear end gears or taller rear tires to help a little. Or drive slower than 70. A TH400 is a good transmission! Would it be worth it to install one of those Gear Vendors overdrives that bolt on where the tailshaft housing goes? It might take less work than swapping transmissions if it'll fit. You might be able to bolt one in and just get a shorter driveshaft. Those overdrives cost big bucks though last time I checked. If you're not doing much drag racing, maybe just put in taller rear end gears. It's a light car, so you'll still have a fun ride even with ~3.00:1 gears.
A th400 is a good trans, especially if you have the hp to need the strength. One of it's problems is a heavier rotating mass and a subsequent parasitic hp loss. Just swtching to a th350 will gain you some efficiency but as was stated, an overdrive paired with the right cam is what you probably want.
You need to find out the cruising rpm for the cam in the motor. You want to be at or near that rpm when you are doing about 70 or whatever speed you want. You'll get the best mpg when in that range. jerry
I'm all Ford so excuse the interuption.I just put an overdrive automatic (aod) in my 40' sedan with a 351 windsor. Dont know about the mileage as most of mine is in town/freeway but it sure is nice to be able to cruise along at 70 mph and 1700 rpm. I think you'll find the swap worthwhile from this aspect alone. Ron
Do you have a dist with a vacuum advance?It will help gas mileage as well as a proper curve on the mech advance.
If you changed the gears to something like 3.40-3.50,you would achieve the same result and would be much cheaper. Try driving a little more conservatively also!
YEA YEA...BUT THATS ONLY FOR THE TRIPS....THE LOUD PEDAL WILL GET DEPRESSED TOO...YOU CERTAINLY KNOW THAT!!!! Can somebody give a shout out about your experiences with the TV cables adjustments on these OD trannys...good? bad? worth it?
200 r4 trannys.... p,m louver dude and ask him how he feels about them things... his is gettin yanked out in favor of a tremek 5sp
I'm running 4.56 rear gears behind a 2700 stall converter to couple the 440 to the pavement, gets around 10 mpg on the highway turning around 3400 rpm at 70mph. The fuel cost is offset by the grin factor and I love the push in the back when I hit it. Just my opinion.
I have shelled many 200-4r trannys, if you don't have the tv cable just so, they will eat themselves. never had a 5 speed go bad, in any of the high boost cars I've had, no matter how much sideways driving I throw at them. the gear vendors setup may cost more now, but surely less after you have to replace just 1 bad 200.
my 34 ply has a 350 ci 700r4 with 3.00 gear, still have a little grunt in first gear because of the low first in the tranny . defiatly not a racer though which is ok with me,22 hyway at 70 mph,the carb cable isnt rocket science if you do your homework,can never figure why nobody made a simple kit for this application,if dough isnt a factor ,like was said Gear Vender is a pretty stought unit,just the price is a killer.also the 87 700 is the toughest of all of em stock
Gear Vendors overdrive ratios .80 overdrive. 700R4 overdrive ratio .70 200-4R overdrive ratio .66 In a light car like that, any of the above would work. FWIW, Art Carr has built many 200-4R transmissions for Buick Grand Nationals. Gear Vendors has the strongest piece and can be ordered for a car slip yoke type application, or truck fixed yoke type application.
got a 700r4 in my A roadster, zz4 350 witha 750Holly (vac sec with meter plate)....70mph comes up at 1750 rpm, 80 at just over 2000 rpm... around town and on a run when not using the O/D 4th runs 15mpg, will get 25mpg on a run in O/D 4th cruising between 60 and 80..even when towing a caravan!!! Got no complaints about the trans it's real good. only probs are the TV cable needs to be adjusted just so or you end up with a box full of broken bits but there has been a thread on here about how to do it and if it gets to 220deg it's cooked so fit an auxiliary trans cooler
this is basically gonna be a street driven car, guys, not a strip driven one, as I am soon to be retired and wont be able to afford breaking and fixing, breaking and fixing...on a frequent scale like I have in the past.(..I have to teach my right foot new tricks!) The urge is always there. I have read about the 200-4r tranny and it sounds like it will work for me if i keep my foot trained. I agree the old stanby T400 is damn near bullet proof behind warmed up motors, but the fact is...my motor is pretty stock, so I dont think I need to have the beefier set up. Would you if you were in my shoes?
what's your converter stall at? 1900 cruising won't do you much good if your converter has more than an 1800 stall unless it's a lockup unit.
I'd keep the TH400 in there just for peace of mind. Sounds like maybe a gear change or adding one of those Gear Vendors overdrives might be your best bet depending on how much money you want to spend. I can't see pulling a TH400 to replace it with some barely adequate transmission. What a waste of a good TH400. I was a Chevy guy most of my life, and went from Powerglides to TH350s to TH400s in lots of different hot rods and daily drivers. The TH400 was always my favorite. Always bulletproof. I'd stick with the TH400. They put TH400s behind big blocks of the late '60s putting out 500 foot pounds of torque from the factory. They're the ultimate automatic transmissions in my book.
Gear Vendor's Overdrives run about $2500, but are transferrable to another car. I'd put one on my 34 but there wouldn't be much room left for a driveshaft, of any length. I have a 350/350hp with a Th400 and a 2.73 Vette rear. My mileage sucks. 10 -12 around town, 15 - 16 hwy. A 200-4R or a 700r4 would probably be my only savior. That and upping the gears to a 3:30. So based on my limited experience, I guess my recommendation would be to use a Gear Vendor Overdrive or change out the trans. Skip changing your gears, probably wouldn't give you much improvement anyway.
I think Rustybolts has some sound ideas here. In a light coupe w/a low first gear, you'll have plenty of acceleration. The 3.08 gear out back will be more efficient than an overdrive. The best part is the car will have "long-legs" in each gear. W/a similarly geared Muncie, it was easy to hit ~60mph, in first!
My coupe had a 350/Th350 combo with 2 big old AFB's, a 350hp 350 cam and a 3.00 rear with 29" rears and got 20 MPH on the road and not bad around town either. I think your gears are killin you!
man...only 20 Miles per Hour on the road....I think YOUR gears are killin' ya...HA HA HA HA!!!!! (I MEAN WHAT YOU KNOW....?) THANKS FOR THE INPUT...
Heard/read a lot of horror stories about frying trannys due to bad tv cable adjustment. I set mine (Ford AOD) with a pressure guage per the instructions. No problems after about 3500 mi. Ron
once in high gear and on the high way the final gear ratio will determine your mileage it wont make any difference what tranny you have its the overall final that make the difference. you can use the t400 and a high gear in the rear or a overdrive tranny and a lower gear and end up with the same final. modern overdrive trans have little to do with mileage and more to increasing performance at lower speeds due to the lower rear end gear used and 4,5 or6 speeds in the trans.
I'm not saying you shouldn't change it if you want to, but for a few more mpg, I doubt a swap will be cost-effective for the annual milage you're talking about.
Go for the 700r4. Have used them in three cars and never had a problem. You have a good lower end and good top. Best of both worlds.
The fuel cost is offset by the grin factor and I love the push in the back when I hit it. This is the TRUTH !!!!
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