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Discussion Starter · #1 ·
I run 4.11 gears in a '68 Elky with a 350, 350 combo with the Edelbrock RPM package. I run at 50 MPH @ about 3000 RPM's to the track and I'm thinking overdrive.
Anybody running a 700R4 and racing ... please post your thoughts!!!
I'm concerned with the gearing. With a 3.06 first gear, when you shift to 2nd, I see a hugh RPM drop. Will the tranny hold up to 450 HP? (500 HP?) I think it's about 3 inches longer... that's means cutting a drive shaft.
Any help will be appreciated!
Phil
 

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I have a 700r4 behind a warmed over 350 in my 70 Chevelle Malibu, 2.73 open rear and 15 wheels. I haven't raced it, ....yet.

The overdrive gets great gas milage, and crusing rpms are low. Not too responsive after you are at speed (rear gears and over drive). Kinda obvious there.

The over qualified "shade-tree" mech. I take the car too every now and then is a hard core drag racer. He thinks I must be a "gas-milage" freak, to run the 700r4. I shrug and say I bought it that way, which is true. He prefers a 4 speed or at least a turbo 350. If ya want gas milage he says, ride a bike. I did when I was younger, bad accident, lost a leg, so now stuck with automatics, "sigh".

I think I am gonna put a 12 bolt I have in with 3.07 gears too see if I like it.

So, in answer to your question, those were my mech.s and my thoughts. But I think it's supposed to work out to overdrive = gas milage = low cruzing rpms, throw a better gear in there, ....well I'll let you know.

------------------
DG
Springfield, Ohio
70 Chevelle Malibu
[email protected]
www.wright.edu/~s001dga/chevy.htm
 

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I just finished doing this in a 1/2 GMC pickup.

I had to cut the drive shaft 2.5 inches, move the cross member mount back and re-drill the frame.

I have 3.08 gears in the rear end and it is way too tall, RPMs are too low unless you are well over the speed limit.

On the garage floor is a new 3.73 ring and pinion, installation kit and Eaton positraction center section. I may get around to it this weekend.

There is a transmission person by the name of Art Karr (spelling?) that contends he can build one that is hard to break.

Precision Industries also makes similar claims.

The theory is good, a killer 3.06 first gear and then I think 2nd is 1.65 which is a big drop. 3rd is 1.00 and 4th is a nice .73 overdrive which is good for the highway.

I spend a lot of time at Maryland International Raceway and you don't see too many of these transmissions unless it is a street rod crowd.

Assuming you run a 29 inch rear tire and shift around 6400 RPM here is what the RPMs and MPH will look like with your 4.11 gears at the track:

1st gear 44 MPH 6414 RPM 2nd gear 3459 RPM

2nd gear 82 MPH 6445 RPM 3rd gear 3906 RPM

3rd gear 135 MPH 6431 RPM 4th gear 4695 RPM

4th gear 185 MPH 6434

You can see the shift from 1st to second at 44 miles per hour will be almost 3000 RPM
6414-3459 = 2955

But you will cruse nicely at 1913 RPM at 55 MPH in 4th gear.

Hope this helps

John


John
 

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The RPM drop (3.06-1.62) sounds worse on paper than it does in the car. As long as you have a good torque curve you won't even feel the drop. The 3.06 first w/ those 4.11's will be pretty much non-existant but you'll definitely feel the difference on the launch. Your first gear will be equivelant to running a 5.00 rear gear w/ a turbo 350. As for durability, I have a 700 behind my very torquey sbc 408. In my opinion torque is a bigger enemy than hp when it comes to transmissions. I've had it about a year, and everything still works fine. The overdrive is awesome. You should see about an 800 rpm drop if you are using a quality converter. If you use a lock-up converter you could see anywhere from a 1000-1200 rpm drop.
In my installation I had to cut the driveshaft, move the crossmember back and redrill the frame for it. Then I just added the correct bracket for the TV cable and wired up the lock-up harness. Wasn't difficult at all.
 

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Hi Phil and the group. Everyone talks about the 700-R4. I will put my 2 cents in here about the 200-4R. Transmission shops have found ways to make these units take the HP. You get a first gear ratio of 2.74 compared to the 700-R4 of 3.06 and fourth gear is .67, about the same of the 700-R4 of .70. The 200-4R is the same length of the 350, so the drive shaft does not have to be cut, but the transmission mount has to moved back about two inches. This trans does not use vacuum in the controls and the electrical side requires a 12 volt signal. If you do go with the 700-R4, install the biggest transmission oil cooler you can.

If you want more info drop me an e-mail. I would like to know how tall your rear tires are, and I have my setup in a 64 El Camino. Good Luck
 

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I agree with ocs408 about the drop between 1st & 2nd gear. My 68 Elky with 468", 700R4, & 4.10 cogs doesn't even notice. The 2nd-3rd drop is more noticeable to me. My 700R4 conversion was the best $800 I've ever spent on my car,bar none. Either it or a built 200R4 would be a great addition to your Elky.
Clint Hooper
68 Elky (468",700R4,4.10, 17" Torq-Thrust II wheels)
 

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This is second hand info, but I know a fella, who runs a tranny shop, uses a 700R4 in his 72 with a 402 and 4:11's. It hasn't broken yet and he is a regular at the local 1/8 strip. He basically said that unless you have a really ball-z BBC, it's fine. But he doesn't run much stall, ( & cam ).
 
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