th 350 for autox?

[chevelletiger]

The 5 or 6 speed isnt going to happen this yr so...will the th350 with my 3:73 rear gear work good in my 72 chevelle?thnks!

[79-TA]

I still run a 350 in my Trans Am, but with 2.73's and it actually works pretty well with the tall rear gear. That is, first gear is just right for most medium sized autocrosses. Also, the unprepared and dusty surfaces of where most autocrosses take place means there's no need for the aggressive first gear torque multiplication. Doug Renner ran his Camaro with a 350 and 3.08's and did well. My small tire diameter and his large tire diameter meant we actually had about the same effective rear gear ratio. A lot of the 6 speed cars just get off the line with first and get to second as quickly as they can. That is, their first gear isn't doing them a lot of good.

With the 3.73's you'll just have to know when to make the shift into second and if at any point it'd be worth dropping it back down into first (forcing it to shift back down without the ability to rev match isn't smooth and can cause the rear wheels to lock up, probably not worth it.) The biggest problem with your 3.73's and no overdrive is what a pain that thing will be to drive on the freeway when going to and from events.

So yea, go ahead and autocross the 350. Be a bit wary if you're running in extreme heat. I managed to boil the the trans fluid once, but that was with everything overheating. A good transmission cooler can provide some peace of mind.

I see you're in Santa Ana. Are you looking at attending any of the events this Fall? In particular, there's the SoCal Challenge at Adam's on September 8th and then Return to the Coast in October.

[chevelletiger]

Hi brett,i will attend the fall events but not with my car,im still not finished with putting the car together.as a note im running a 18x10 rear wheel with 305 35 18 tires stepping down to 295 soon tho.i think. I might be wrong but would i need the 3:73 to get that big of a tire moving?thanks again brett hope to see you at the events in the next couple of months!phil

[Steve Chryssos]

You sure can. With autocross, second gear is second gear. Neither the car nor the course cares what trans you are running. With my 3.73 gear and almost 26 inch tall tire, I launch in first then shift into second and run the entire course in second.

[SLO_Z28]

What size tire are you running in the rear? I love my TH350, and I race all the time with it.

[chevelletiger]

What size tire are you running in the rear? I love my TH350, and I race all the time with it.
Nitto 555r305 35 18 going to step down to a 295 35 18

[musclecarmatt]

i run a TH350 in my car....at GG autox with 3.42's i can run 1st gear pretty strong...does pretty well!

[SLO_Z28]

Nitto 555r305 35 18 going to step down to a 295 35 18

That nets you 45MPH in first at 5500RPM, and 2nd gear is 35MPH at 2500 and 75mph at 5500RPM. That makes second gear perfect for autocross as long as you have a decent amount of torque (which its hard not too with a 350).

[chevelletiger]

Thank you guys for all the good tips,not having to jump so fast to get a 5 or 6 speed stick for this car will save me a bunch rightnow it been 6 to 7 yrs building this car),all cash no parts bought with credit cards so it will be all paid for when im done.phil

[SicMonte]

I run a 200r4 in my car in second gear all day long at the autox. It's fine for me!! I will say that if you ever want to do any serious road course racing then a manual is a must. I was at Mid Ohio last week for a track day and my automatic hit 225 degrees really quick, and thats with a HUGExHUGE derale cooler with a fan on it! It eventually started to spit fluid out of the vent and I got black flagged once b/c my car was "smoking".

[Steve Chryssos]

I run a 200r4 in my car in second gear all day long at the autox. It's fine for me!! I will say that if you ever want to do any serious road course racing then a manual is a must. I was at Mid Ohio last week for a track day and my automatic hit 225 degrees really quick, and thats with a HUGExHUGE derale cooler with a fan on it! It eventually started to spit fluid out of the vent and I got black flagged once b/c my car was "smoking".

An expansion tank such as in the link below as well as some Red Line Oil D4 will go a long way towards improving road course performance. The tank, gives the fluid "breathing room" which not only captures overflow, it keeps the fluid from seeing excess pressure. Upon cool-down, the transmission sucks the fluid back in. The Red Line Oil D4 is stable beyond 300 degrees F and usually shortens shift time, as well.

Moroso Transmission Expansion Tank (http://twistmachine.com/shopping/index.php?main_page=product_info&cPath=6&products_id=71)

[SicMonte]

An expansion tank such as in the link below as well as some Red Line Oil D4 will go a long way towards improving road course performance. The tank, gives the fluid "breathing room" which not only captures overflow, it keeps the fluid from seeing excess pressure. Upon cool-down, the transmission sucks the fluid back in. The Red Line Oil D4 is stable beyond 300 degrees F and usually shortens shift time, as well.

Moroso Transmission Expansion Tank (http://twistmachine.com/shopping/index.php?main_page=product_info&cPath=6&products_id=71)

That's a done deal!!! Thanks for the link and info!