I just fried my second 700r4 in my car. The first one lost drive and overdrive all together and this one is starting to slip when going into drive and overdrive. All of my buddies say that I should swap in a 350 turbo. I have never had anything with a 3 speed in it, so I was wondering if it would be like driving my car with the 700r4 in drive or if the 350 would be somewhere in the rpm range between drive and overdrive of the 700r4? It has a built 350 and 4:10 gears. It is not a daily driver just more of a weekend toy and rarely ever driven on the free way. I'm thinking if I go with the 350 turbo that I might gear up to 3:73's. Any one with any suggestions?

 

Nothing wrong with driving around without an OD. GM did it for decades. Everyone just wants an OD now to drop the rpms down while on the highway to save fuel.

The 700R4 is a great street transmission. It provides a deep first gear to go with highway gears in the diff plus has the OD to really help out on the highway. The downside from a performance issue is the extra gear spinning around and the poor 1-2 gear ratio. At WOT, the gear spread between first and second is too far apart.

TH350 is a good all around tranny. It has good gear ratios and parts are plentiful although they haven't been in production for many years. GM produced millions of them so they'll still be around for a while. Downside is the lake of OD for those who feel they need an OD. The intermediate sprag is also weak. When you lose second gear, you'll know the sprag blew up from the hard parts you'll find in the pan.

A better alternative is a TH400. Slightly different gear ratios than the TH350, still no OD but a much beefier transmission capable of holding more torque. You really need to see what a TH350 and TH400 look like inside to understand why it's stronger.

If you need an OD, a good choice is the 200-4R. It has the same gear ratios as the TH350 plus has the OD. These transmissions work well behind Grand Nationals.

 

maybe you didn't have the TV cable set properly, its key to a long life transmission. the 700r4 is a great transmission if built right, and only costs $100-$200 more to rebuild than a 3 speed, which will be offset by the cost of having to change your driveline length if you went to a th350/th400, amongst other things. just had a 700r4 rebuilt at my local builder, best in town since the 60's and family owned for $900, included master rebuild, 5 pinion planetary, beast shell, transgo shift kit, 1800 stall converter, new TV cable, dipstick, speedometer gears, hydraulic lockup, 18 month warranty. can be had for $300 less without all the upgrades i did.

find a reputable builder and have it done right, and set the tv cable right. you won't regret it.