Anybody have a th350 and love it? I am trying to decide between a th350 and a 700r4. Modest horsepower v8 going in the truck. Don't plan to hotrod around town. Will only be on freeway occasionally. Keep hearing about poor freeway mileage and high revs in the th350 but wondering about the thousands of th350 in many different cars and trucks for years and years. I'm not opposed to the 700r4 but seem to have better access to TH350 and engine combos on craigslist. Anyone want to weigh in on the subject? Thanks

 

Hard to beat simplicity. With a modern V8 you have plenty of power to use a low-number rear axle to keep revs down.

 

I plan on freeway driving so I have the 700R4 in mine with a 373 gear 8.8 rear. A friend of mine has a TH350 in his truck and likes it, most of his driving is short trips. He also has a 3.08 rear. I do have a TH350 that came in my truck when I bought it that anyone can have for free. It supposedly worked fine but I had access to the 700R4 and switched it out. It is a long way to ship one that may or may not work, but if anyone is close and wants it let me know.

 

I agree with Ross. For most driving, even with modest freeway driving, the simplicity of a 3 speed auto with modest rear end gears is a tough combo to beat. Lower cost is also a plus. I am running a C4 behind a 289 with 3.25 gears and it gets decent mileage (16 around town), good power, and runs at 2150 rpm on the freeway at 55. Simple but works fine for me.

 

With a modest HP setup you cant beat a 700r4, only issue with them is setting up the TV cable correctly. Once that is done you are good to go. The OD and steeper first gear are both advantages, especially the OD on the highway even with a lower numeric rear gear. Keeping the RPM down is the secret to good gas mileage. The ones I use are from 1987-1992 F bodies, 2wd truck would be similar but probably different valve body calibrations. The 87 up 700s have the factory upgrades and you can identify them by the large MD8 cast into the side of the bellhousing. I run one in my 37 Buick now from an 87 trans am.
I used to always run TH350s in the 1980s and 1990s even behind my BB chevy engines. I always install a B/M transpak on level II and never blew one up, but depending on how tall your rear tires are a 3:08 was about as steep a gear I would run with one on the highway just to keep the gas bill down. I used to run with 3:55s and 3:73s, fun around town but not on the highway. I still have a couple on the shelf but once you have OD it is hard to switch back. With the 700 you can run a 4:11 rear gear no sweat.
Use a speed / gear ratio calculator to really find out what the truth is with your combination, I use it for every build. Plug in tire height and rear gear and you can see what your RPMs will be in each gear at any speed with or without OD. I shoot for 2000-2200 RPM at 60mph generally but I do hit the highway frequently.

 

On the subject of simplicity. What makes the th350 more simplistic than the 700r4? Does it have to do with the installation, maintenance, reliability or something else?

 

I worked at a Pontiac Dealership in the late 80s and back then the 85-86 firebirds would come in on the hook and they had oiling issues with the sprags and they would be COOKED!

There are way more parts inside a 700r4 compared to a th350, but I think the benefits of the overdrive are worth it

 

I have run many 350/350 combos over the years. I don't ever remember getting over 16 or so mpg on the highway with one.

The last few 350 engines I have put in cars have had the 700r. MY 39 ford had a ZZ4 350 and 700r. It gets 26 on the road with 3:55 gears and runs about 2000 to 2100 at 75 to 80mph.
I would use the 700r.

Larry

 

I put a built 700R4 behind a 350 in my F4. pulling 4:10 gears and 31 inch tires. Runs down the highway at legal speeds effortlessly. The TV cable was not all that hard to set up, once I understood what I had to accomplish.

 

Nothing simpler about the TH350 other than you have to set up the TV cable correctly on the 700r4. TH350 controls shifts with a vacuum modulator, 700 uses a throttle valve which controls line pressure and shift points to a degree. The TV cable has to be set correctly otherwise the trans will burn up, but there is plenty of information out there to get it right the first time.
As insurance I put a will put a pressure gauge on the 700r4 and check line pressures before it leaves the garage just to verify all is right.
Another benefit of the 700 is the lockup converter, I have mine set to lock when shifting into 4th gear. Drops the RPM a couple hundred more for even better mileage.

 

+1. There's a reason it's called a 700. It's twice the transmission the 350 is.
A properly set up 700R4 is superior in every aspect to a TH350. You can run a taller rear gear and not lose any grunt off the line with a 700R4's deeper 1st gear, and gain an even greater benefit from the overdrive on the freeway. Win Win.

The 700 has been around long enough that the aftermarket has solved all of it's early issues, and they can be built to handle gobs of torque and live as long as the engine does with normal maintenance.

 

Just wanted to thank everyone for their experience and opinions on this question. I can now make a decision. I am tempted to post this same question on the corvette forum. I suppose the answers may be the same but I know for sure the spirit of cooperation and helping will be suspiciously missing. Perhaps that is the reason my corvette sits alone while all of my attention goes to my truck and this site. This site really is the best. Thanks

 

IMHO, which you choose should really boil down to what rear gear ratio you're running. I'd use the TH350 for a rear end ratio of 3:25 or lower and the 700-R4 for anything numerically higher than 3:50. You could use either for ratios between 3:25 and 3:50.

 

If you're considering the 700R4 you might want to look at the GM 4L60 / 4L80 transmissions. Late 1990 early 2000 variants are supposed to handle lots of torque.

 

computer control only. 1992 would be the last year of 700r4 I would use, 1980 for the TH350 (81 up was lockup torque converter).