shua1269

Hi there, So I have been contemplating many motor and tranny swaps in my '74 stingray. It currently has a 350/ 3speed auto. I have the opportunity to build a 406 small block that one of my buddies has just sitting around planning on pushing close to 450hp/tq. I also obtained a 700r4 tranny.

I have done a lot of researching and have seen a few 700r4 swaps and some say the drive shaft needs to be modified and others say it does not. I have not seen many 406 swaps though...

My questions are these:

1)Has anyone done a 406/700R4 swap in their C3? If so, what other modifications were needed.

2) What are the biggest challenges with swapping the 700r4?
(I know the 406 will bolt right up to where the 350 was)

3) What gear ratio should I go with for the rear end? It will be a weekend cruiser and occasional strip car.

cv67

What are internal engine specs? That will help you choose your gear/converter.

Heads
cam
intake etc.

shua1269

4 Bolt Block .030 over, Don't have Crank yet, Hypertectic Pistons, Reco Rods is all I have so far. Like I said I'm going to be building the motor. I don't have the heads, cam or intake yet. Trying to get an Idea where to go. Mostly looking for tips on the install of the motor and tranny. Any issues that people have come across.

jackwabbit703

I have 406 roller but do not have 700r4. Wished I did.

make sure to do ARP stud upgrades.

I'm pushing close to 500 torque running 7.5 second 1/8th on a 4 speed m21 with 4.11 rear gears.

I would put in 3.73 since you'll have over drive gears. If you want 4.11, you'll need 4 series carrier so, stay 3.73. It's a wonderful gears.

shua1269

Awesome! Thanks! Did you use an aftermarket block or an original block? What heads, cam and intake are u runnin?

hugie82

The 406 is the easy part . The 700R4 is a little more involved. A few things you'll have to deal with.
The lock up converter will need a kit from B&M
The trans is longer but the yoke should be the same as a th400
You can use your stock shifter but you won't have low 1 unless you notch out the shifter gate.
You'll most likely need speedo drive gear to get it reading correctly.
A new converter with a different stall speed won't be necessary unless your motor is really cammed up. 1st gear is very low and off the line launches are fast!

This is based on the assumption that you have a mid to early 90s 700R4...


Its not too hard but a lot of work but worth it

shua1269

Awesome! Thanks for the great info!

jackwabbit703

Sent you PM on what my 406 have.

shua1269

Awesome! That's one bad Vette!

lionelhutz

Sounds like you'll have a fun car once you get that engine built. If you can swing a little extra cash and are OK with more wiring and using a computer in your car then a 4L60e will work way better than a 700R4. Just saying, if you're going auto you'll love how you can setup the shift vs throttle points for each gear and for the lockup. It'll shift right where you want every time. I won't use a valve body trans again.

The driveshaft will have to be shortened about 3" but you should install the trans and measure just to make sure.

shua1269

Thanks, I already got the 700r4, so I'll probably just stick with that and thanks I will definitely measure, just saw conflicting info on it.