what would be advantages and disadvantages of installing a TH350 in place of my 700r4 on my stock 89 rs?

 

Disadvantages: You lose 4th gear, and therefore gas mileage.

Advatanges: I would say it depends on what you are doing with the car. Engine specs, time spent at track, is it a dialy driver, etc. If you are keeping it stock I don't think it would be wise to swap a TH350.

 

In the vast majority of cases there isn't any advantage anymore.

 

except for the th350 is ALOT cheaper

 

TH350's are cheaper but you're getting less transmission so it makes sense. Not only does having an overdrive give you better gas mileage it allows manufacturers to lower the first gear to a much more enjoyable level. I'm probly gonna get flamed for this but off the top of my head i believe the TH350's had a 2.52 first gear ratio while 700's had a 3.08. Please don't hesitate to tell me if my numbers are off its been awhile since i looked at them. Long story short to get the same low first gearing as a 700 a 350 would need a lower rear diff. ratio which also costs more money. Sigh...seems like its impossible to come out of a project cheaply.

 

tighter gear spacing allows for lower ET due to keeping the engine in it's powerband longer. Trans is stronger for cheaper, and converters are cheaper. For a daily driver I'd be against it, but after burning up 3 700R4 trans locally, I wouldn't go back.

 

GM produced millions of them in cars and trucks before OD was offered. It's lighter than a 700R4, uses less power to turn the internals, performance parts are cheaper.

The 700R4 is a great street tranny. The low first gear offers better off the line performance when the diff has highway gears in it and once into OD, the engine rpms come down even lower to offer good fuel mileage.

The TH350 has a better gear spread. Unlike the 700R4 that has a wide 1-2 shift which drops the engine rpms down too much during WOT operation, the TH350 allows the engine to stay in it's powerband better with a closer gear ratio.

If your car is street only, use a 700R4 and don't put too deep of a gear in the diff. The low first gear of the 700R4 combined with a deep diff gear can easily overpower most street tires.

If you're building a street/strip car and don't care about better fuel mileage on the highway, put in a TH350. If geared properly, you're not going to use OD on the dragstrip.

A better alternative is a 200-4R tranny. It has an OD and has gear ratios similar to the TH350.

 

thanks for the write ups guys