[whacker55]

Here's the setup I have:

1968 elcamino custom
496 BBC stroker motor aluminum heads 600ish lift cam 10.5-11.0 CR roughly 600 hp 700lb tq ( estimated )
th400 with lower first gear than stock with 2500ish stall.
energy suspension poly trailing arm bushings
competition engineering traction bars
stock shocks
stock springs
3.73:1 12 bolt positrac rear end
275 60 15 tires on 15x8 rims 4.5" backspace

seems like every time I give it any gas the rear breaks loose and I have to seriously feather it. I want to be able to cruise it on the freeway out of town but I don't want to loose alot of bottom end.

Is running a 3.08 rear gear going to severely rob my hp and tq? What are some of the BBC trans rearend combos that have been successful for you guys?

It seems like I could run a gear vendors overdrive but 3200$ is not on the budget as of now. Maybe I can find a happy medium until then?

 

[Brian Ferguson]

Thats enough power you could probably run whatever ratio you want and still smoke the tires. Maybe try some slicks. lol

 

[big gear head]

Why the low gear in the transmission? You didn't mention the stall speed of the converter. That's going to be the limiting factor for the gears. If the stall speed is much higher than the cruise RPMs then the converter will heat the fluid and could burn up the transmission.

 

[whacker55]

The reason I have the low gear is the th400 is a HD version pulled from a diesel PU truck. Just had it reworked for my application. Was running a close-to-stock 350ci before. Figured the lower first would help get it up and going faster better @ 280 flywheel hp 300 tq. Didn't figure on the BBC coming into the picture so soon.

 

[big gear head]

The low first gear is helping you smoke the tires. If you had the standard first gear it would be better. What about the stall speed of the converter?

 

[whacker55]

2500 ish stall

 

[big gear head]

You might get by with the 3.08. Be sure that you don't get a Richmond 3.08. Get a US Gear 3.08.

 

[68454SS]

I have a torquey 468 with a standard 400 trans. and 2.73s and it's a handful. I can only imagine your problems. Maybe install a super heavy throttle return spring?

 

[whacker55]

Haha. No kidding. A deadenbear throttle stop too. I am gonna try a 336 set I have laying around. Then we'll see what happens. Nothing like swapping gears. Practice makes perfect. Just have to locate my case spreader.

 

[big gear head]

Bigger tires helped me.

 

[whacker55]

Hayyyy wait a minute. That's not a chevelle!


Just kidding. Looks good!

I'm running 275 60 15 MT ET Street radials right now. I can sorta hook em a little if they get warm first.

 

[whacker55]

Sorta big?

 

[z15cam]

Mines not a Chevelle either but were would we be without the other to trade parts with ;o)

I’m running a 600Hp SR 460BB in a 70Z body, M21/3.08’s as a HWY Warrior and love it. I live in the country. The only time I have to feather the clutch is when I 1st start her up and have to navigate parking lots when the engine is cold. Believe me she will smoke T/A P295’s in any gear.

I would recommend an M20/3.08’s for City and still boogie on the Freeways.

 

[whacker55]

Well Thanks for the replies guys. I appreciate it.

 

[BillyGman]

Bigger tires helped me.

Gorgeous car!!! :thumbsup::thumbsup:

 

[big gear head]

Thank you.