th350 or 700r4

[lax54650]

i am still debating about which trans to put back into my truck. i have a basicly stock 350. dual plane intake, small cam, block hugger headers 500 cfm eddy. 3.08 gears. i have the original th350 long shaft that needs to be rebuilt. would i need to alter the drive shaft to use 700r? or just move crossmember back a touch. will it be too sluggish in od?. will i actually gain any mpg? is my rear too high geared? or would it be useable? i believe i can get a 700 built for around $800 and the th350 for $500. please let me know all your thoughts is there anyone running 700r 3.08s what tire size? and do you like it?

[Gray Ghost]

If you know a reliable builder the 700 would defintely be a better choice. You will gain mileage and the axle ratio is not too high at all.

[68Stepbed]

In the long run, the 700R4 will give you more options. If you have to rebuild either way, I would go with the 700R4. I wanted to put one in my truck, but I had a great TH350 with everything already set up.

The 3.08 gears will be fine. You might eventually want to change to 3.42 or 3.73 gears later, but for now it will be fine. Around town you might just leave it in D and put it in OD when you get on the freeway.

You will need to have your driveshaft modified AND move your crossmember back. That doesn't cost very much though.

[N2TRUX]

700r4 is a no brainer. It has a lower 1st gear and a higher 4th gear than the 350. If built correctly it will do everything a 350 does and a lot more.

[3quartertime]

I'm having the TH350 rebuilt for my 71 K20 right now. I actually had this conversation with the tranny guy yesterday. He said the 700r is definitely a better option, but a well built TH350 isn't bad either. It depends on what your goal with the truck is. A daily driver or weekend cruiser. My goal is house project work truck/ back-up transportation. So the extra bucks for modifying the drive train can go for other stuff. Hopefully someday I'll get to do a full rebuilt on the truck and then I'll probably dive into the heavy drive train mods...

[c10addict]

I have a 700R4 with 3.42s in my 64... What a great combo!! Go with the 700R4

[pmpski_1]

I'm going through the same decision making process right now. Want some good opinions? Lot's of posts about gear ratios and whether it works or not.

http://67-72chevytrucks.com/vboard/s...d.php?t=329240

Remember though, the cost of a rebuilt 700R4 is not the entire cost! You'll need to pay for various other things and it'll end up being (maybe a lot) more in the end.

If price is an issue, rebuilding your 350 and putting it back in is going to be the best bet. The difference is not going to be just 300 bucks.

[wHATANERD]

I've got a 700r4 from Phoenix Transmissions sitting in a crate to go into my 69 when I put the 383 Stroker in it. The engine will not turn as many RPM's and last longer with the OD, and not to mention fuel savings.

[jgreene0717]

My combo is 350/TH-350 with 3.08 rear gear and is ok. But I will soon be putting in a 3.73 gear and will surely have to get a 700r to be able to cruise at 70mph at reasonable rpm.

[MrC1]

No contest. 700R4.

[steelhorse]

Just to throw something out there.I heard that a 200r4 has a better gear split and will bolt right in place of a th350 including the driveshaft.

[1970 CST Short Wide]

How is the 700R4 behind a Big Block? Does it handle torque well?

[mudman316]

Lower first and higher 4th yes but. i had several go bad behind a 283 (lots of torque and heavy foot) that i built both the motor and the trannies maybe i just don't know how to build them well or my motor building skills are better than i think.

with that said there is a kit (i have not had one with it) that is suppose to make them as strong as a 350th . but that is only what i heard about the stronger kit not personal experience. You can only guess that I don't particularly like them.

just my .02 cents worth.

[lax54650]

i did some research today seems that i have a long shaft th350. which is the same length as a 700 r4. so the swap would include moving crossmember back. providing proper tv cable mounting to eddy carb and a wiring kit. priced some used trannies locally i might go with a "good" used one for $350 then in a year or two have it rebuilt. my truck will be an ocasional driver toy no hot rod just a nice lookin truck.

[1971ChevyTruck]

Make sure you have one of the older 700R4 trannys and then thats the way to go. I put one in my truck and it is a lot of fun to play with. I bought all the wiring and stuff from Bowtie overdrives. I think the whole thing cost me about $500, but I got a good deal on a good used 700R4 out of a camaro. I have 3:73 gears and that just about perfect.

[Longhorn Man]

I'll say that your MPG will probably go DOWN running a 3.07 gear with a 700R4. It's been documented on here more than once, and I don't see why yours would be any different than there's.
So IMO, unless you want to spend the money for a rear axle swap (or more $$ on just a rear gear swap) the lock up controller, the TV kit (bowtieoverdrive.com is the only one I would even consider) and a bellcrank correction kit on the carb... all for just a couple hundred RPMs drop... I'd say stick witht he 3.07 gear and the TH350. Your cruise RPM should be right at 2400 RPM right now anyways, and unless your engine is lame, it should have plenty of tug coming out of the hole for any street conditions.

[70clone]

Its not so much that it needs to be built correctly the problem with the 700 r4 is the tv cable controls the shifts and if you hav an aftermarket carb you will need a tv cable corrector holley and edelbrock carbs throttle lever dont have the correct geometry for the tv cable, and if the tv cable isnt adjusted right you will burn up the tranny in the first 10k miles. So just be sure you have it adjusted properly