My car has a 307 with a PG,was thinking about putting in a 700R for better hwy cruising. Has anyone done this and how much does it drop?. My car is only a 2bl and would I need a different bracket on side of carb?
...Engine RPM drops by about 30% , so fuel mileage increases alot usually. Yes you need to get the cable from the tranny to the carb just right as all shift points are regulated by pressure. There may be jobber throttle shafts out there that you can use, or just make one and add it over the existing one that can be adjusted to get the right " arc " to correspond to pull the cable.
The 200-4R would be a good option with the 307. The 200's don't like big torque (i.e. I was told they're good up to about 300 to 350 ft-lb. Beyond that, they'd require some internal mods to get long life out of them. When I looked into it 10 years ago, the HP internals on the 200 were not cheap. If your 307 is 'built', a stock 700R4 would handle more torque.)
Pretty easy swap. No cutting. You'll still need to deal with lock-up on torque converter and the TV cable.
I pulled the torque converter lock-up switches (vacuum and brake) and a TV cable bracket off a donor at the wreckers. Cost me $10 if I remember. The procedure for both is pretty well documented on the internet. I did use a new TV cable (about $50) but a used one would likely have been fine.
The 700 is about 4 inches longer - so the drive shaft needs to be shortened. Not a big deal - likely $100 or so at a machine shop - get it balanced after. The 200's are the same length as the PG's (within a 1/4 inch anyway so driveshaft stays stock).
I think both (700 and 200) require that crossmember be slid back to the TH400 holes on the frame and the tranny mount needs to be changed.
I put a used 200 (it had about 200,000 km on it) in my Beaumont just to try it out. I really liked it but it started slipping after about 5,000 km. When I tried to get it rebuilt, the local rebuilder talked me into a 700 (he had not had good luck rebuilding the 200's). He did the R&R and did tell me the 700 was a much tighter fit under the transmission tunnel, so they may be larger in diameter than the 200's too.
If you already have a good 700, that'd cinch the deal IMHO.
66 Beau, what do you think of the 1-2 shift between both trannys? I haven't driven them, but hear the 200 I has a better gear ratio spacing. The really short first gear on the 700 has me sold on a 200 if I upgrade to an OD.
Sorry for the delay - I thought I had responded earlier but it was from my phone and obviously the post didn't make it.
I definitely liked the gearing of the 200 better than the 700. First gear on the 700 is fun (low gear to get things moving) but the step into 2nd is definitely a bigger step than on the 200. But to be honest, the difference wasn't all that noticeable.
When I had the 200 and switched to the 700, I was running the stock 3.08 peg leg rear end. If I jumped on the throttle, the right rear would just spin with either tranny and keep on spinning through second, so it didn't really make much difference. The step wasn't enough to bog the engine.
The lower first gear with the 700 made the car a little more responsive at low speed or off the line, but without traction, it wasn't really usable anyway.
I've since added a posi and I'm running 3.73 gears. The lower first gear is definitely overkill now, and the 1-2 step is more noticeable - though now when it kicks into 2nd, the rear end tends to want to go sideways (sudden increase in tire speed). It might have done the same with a 200 - don't know but I do have to be a lot more careful getting into the throttle if I am not 100% straight.
If I were running more cam and drag racing, the gearing on the 200 would definitely be better - you'd stay in the the power. That said, the drop in RPM with the 700 really isn't that significant for most engines - unless you have a full-on race cam that doesn't come alive until 5000+ RPM, I don't think the tranny choice would make that much difference.
I figured it'd be better to have something that would stand up to a little fun was worth the minor difference in gearing.
Since you already have the 700R4 I think you should go ahead and put it in.
It will make a world of difference. The car will be much quicker off the line and the overdrive will make it cruise down the highway like a champ.
I'm sure there's a ton of good information on the internet for doing the swap, but I will say it's not that hard, and certainly worthwhile.
Like others have mentioned, the 200-4R swap is actually a bit easier because the 200-4R is almost the same length. You usually don't have to shorten the driveshaft.
And if I remember correctly, the transmission mount on the 200-4R is in the same spot as a Turbo 400, so you just have to slide the crossmember back to next set of holes that are already drilled on a Chevelle or Beaumont.
The 700R4 is more popular and I think it's stronger but they did use 200-R4's in the Grand National Buicks, so I'm thinking it would be just fine behind a 307,,, but since you already have the 700R4 that's probably the way to go. It's a good winter project!
This has nothing to do with this swap but it may interest people to know that the notoriously weak TH-200 (not the 200-4R but a lightweight three speed transmission) has lately become popular with racers in the NHRA Stock Eliminator class.
Those guys will do anything to reduce weight,,, especially rotating weight. It seems they can make this lightweight transmission hold up OK with aftermarket parts.
.....If I remember right from specs when I was building my 49, the 2004R has a .67 4th gear ratio, the 700 is .700, so you got a hair less rpm cruising in o/d. I am very pleased with the 200 4R in my 49 diesel, shifts very smooth and is all I need to roll down the highway, and oh...I have 2.29 rears in back so shift points can be very high if you want but it seems very good powerwise with my only 110 hp !!
