Considering a 700R4 swap

[Cruisinthe34]

I've just begun work on a 1958 Chevrolet Brookwood wagon with a stock 348 single 4 barrel and auto transmission.

I'm intending to build this into a 'daily driver' so am contemplating a swap to a 700R4 trans. If this car has the stock 3:36 rear end, what are the collective recommendations or do I need to change anything ???

Thanks in advance.

 

[Fathead Racing]

I've just begun work on a 1958 Chevrolet Brookwood wagon with a stock 348 single 4 barrel and auto transmission.

I'm intending to build this into a 'daily driver' so am contemplating a swap to a 700R4 trans. If this car has the stock 3:36 rear end, what are the collective recommendations or do I need to change anything ???

Thanks in advance.

4:11s would be a better choice but 3:36 gear should be fine. Take it close to stock on the cam choice for 3:36 rear gear.

 

[wbc409]

The TH700 has the deepest stock gear of all the GM tranny's, so 3.36 gear should be fine. The adjustment on the TV cable is critical, GM has an adjustable one, I got the correct carb stud for the cable from Edelbrock.
The tranny is physically longer so you'll have to get the D/S shortened. The yoke is the same as a TH350/P-G so as long as your yoke is in good shape it should be reusable.
I'm not sure what kind of shifter you want to use, I used a cable shifter with no problems.

 

[petepedlar]

I think 3.36 is a tad high....... I have the 700R4 in my Impala with 3.08 gears.... It's at about 1400 RPM at 60 MPH...... the first gear is fine. There is a couple of good gear calculators, Richmond Gear has one.... that will tell you RPM/Speed. I'm changing mine to 3.55's which will give me about 1900 RPM @ 60.

Ray's 4.11's would be fine as well...... depends what you want the car to do. Better 1/4 mile times with the 4.11..... little better cruise RPM with 3.55's or 3.73. Personally I think 3.08's or 3.36's are two high geared. I wouldn't want to try and cruise at to low an RPM......

I bought everything to make it work from Bow Tie Overdrives.... but there are other suppliers as well

Just my opinion...

Dave

 

[jim_ss409]

The 700R4 would be really nice. The 3.36 gears are higher than you need with the overdrive but they'll still work fine. If you never even used 4th gear it would still be a lot better than the Powerglide. Like the other guys said, with the overdrive you have the luxury of being able to use a low rear end gear and still be able to cruise at a lower rpm. It's a bit of work to do the swap but the results are really good. You'll see improved acceleration AND better mileage!

 

[mac1]

I had a 3.36 rear with the 700r4 and a 283. It would bogged down a some with my little 283 when the lock up converter engaged at 45 mph, so I got an adjustable lock up converter switch from BTO and set it to lock up at 60 and that solved that problem. I really didn't save any gas though. With the power glide, I would do 55-60 in the slow lane. With the switch to the 700, I found myself doing 80 in the carpool lane. Oh yea, I got to the shows in record speed. LOL
If you can keep your foot out of it, I think you will be happy with the switch.

 

[hogmotors]

One thing that I don't see mentioned a lot is the quietness when you have overdrive. We never realize how nice it is in a cruiser.

 

[Cruisinthe34]

Thanks for all the input folks........700R4 it is then !! I have a 700R4 behind a 350 in my '34, and a Ford C-4 behind a Flathead in my '41, so I'm accustomed to redoing drive shafts and somewhat difficult trans exchanges i.e. the '41.

I think I would prefer a set of 3:73 gears, but as long as the 3:36's aren't a show stopper, we'll proceed.

 

[61BISCAYNE]

Remember, most of the 1988 thru 1997 Chevy 1500 pickups have
3.42 rear gears, and they are pretty torquey in low gear.
Considering they also run taller tires than most of our
cars, the overdrive should work quite well with 3.36 gears.
In fact, the effective gear rear ratio at the axles of a 700R4's low first
gear mated with a 3.36 rear gear is the equivalent of a turbo350
transmission twisting a 4.0 gear in the rear.

 

[Fathead Racing]

It's not about 1st gear ratio in an everyday driver, it's about cruise rpm and the peak torque range of the engine. You have to be aware of the limits of the 348 at lower rpms when you pick the components for the engine, cam, carb, timing etc. Pick a gear that will not lead to detonation on the thruway. You don't want to lug the engine at speed, find the sweet spot in terms of rpm.