camcam

Long time lurker mainly used this site for knowledge but after starting to get more serious about doing trackdays I thought I'd join and post something since there isn't too much info on this topic.

Anyway, car is a '02 automatic coupe with some moderate power mods (ported 243s, medium cam, headers, cai etc.) pushing around 430rwhp/402rwtq. Stockish suspension but that will change soon for more serious driving. However as you can tell, it's an automatic and that is never thought of as a good unit for this type of racing.

This car has been in the family since brand new and my wife loves to drive it but cannot do stick for whatever reason, so ultimately it would have to remain an auto. Just trying to see if it's even worth it to try and build the transmission or not even bother and find something else for road racing.

I have a friend with an RPM Level 6 I believe unit and he's pushing 700rwhp through a procharger and that thing has not skipped a beat on the street or many drag strip visits. However I do understand that road racing is alot more stress than quarter mile stints, so it's not a simple apples to apples comparison. Although my car is putting down a helluva lot less power than his.

So if I build this unit with premium components (billet shafts, Sonnax smart shell and input drum, 5 pinion planetaries etc.) will it be possible for it to live on such a demanding race...or am I just simply on borrowed time regardless of how much I build it?

ErnieN85

It will hold up if you get additional cooling (as much as possible)
the only other thing is to make sure it doesn't pick and chose down shifts on it's own! coming out of a corner applying throttle and it shifts down about as bad as it gets

camcam

Cooling should not be an issue. Stock transmission with a 3000 stall maxxed out around 210* even on a hot ambient day. Cooler is a big Derale stacked plate with fan. I will be going with a similarly sized stall but probably do a triple disk to lock at WOT so temps will be even lower than before.

The tune and HD2 shiftkit have really helped be able to manage the right gear and never got a miss-timed downshift. Pretty much keeping it in gear manually and worked really well.

But good to know that as long as temps are kept in check the unit can survive.

fleming23

For what it is worth, I had a Jake's Performance 4L80E and Circle D single disk 3200 stall with a pretty decent external cooler under the front nose of my Corvette and managed to fry it in a single day on track. Prior to the track day, temps were never much above 200 and tended to hover around the same as water temp.

I just didn't have it designed to cool enough when going hard for 25-30 minutes. I didn't have a dedicated trans temp gauge but when I pulled the data from my laptop the temps were 250+.

Joshboody

There's a built c6 auto on sticks pushing 500whp in our club... not sure of any tranny mods. He runs flat out for 20min in 95deg temps and 1 of the fastest on the track.

camcam

Oh yeah that'll do it. From what I know about auto tranmissions is that heat is a killer and 250* is almost instant failure. And if you were seeing over 200* on the street I'm not surprised you got that much on the track. With my setup I have a hard time hitting 170* outside of a racetrack. I'd have to be ripping on it alot with the converter unlocked to even break that barely.

Is he on here by any chance? And is it the 6 or 4 speed auto?

Joshboody

Its a 09 convertible I think. He does have paddle shifter, so I guess the 6 speed.
Not sure if he's on here.

AND0

my advice would be to forgo the trans build and put as giant a cooler on there as possible.
You are not exceeding the trans' power holding ability just it's cooling.
High stall converters unlocked add massive amounts of heat.
Stick with the stock converter to keep cool, big a$$ cooler and run it at a track day, watch the temps, build appropriately.

camcam

Right if you read my second post I noted some results from 2 trackdays done already and temps are not an issue at all. More that I'm running over 100rwhp more than stock and want to make sure that I build accordingly. The stock unit has been ok so far but can't expect it to go much longer at this power especially when putting more stress on it than just "aggressive" street driving.

VGLNTE1

If I had a auto, I wouldn't even waste my time road racing. But that's me.

AND0

Sorry, with the drag strip talk, I kind of assumed you were referring to a day at the drag strip, not race track track days.

Still, I would advise the same, if you are running track days and the trans is holding 210 degrees then stay with that. Spending a bunch of money on an automatic track car is going to be an exercise in frustration, and a severe limitation if you get at all serious.

0Anthony @ LGMotorsports

We have had a few customers road race auto cars. While it is harder to do, and you have to change your driving style a little bit...it can be done.

Worst case we have seen was a C6 GS with a Procharger and 6 spd auto. That was a lot of work to keep that car cool. It had a bigger radiator, dual fans, HUGE oil cooler, and external trans cooler with additional fan ducted through the fender.

So you have to watch the car and what you are going to see temp wise. For those of us in the southern US when we have to deal with 104+ degree days you should think about adding a second cooler to the trans. I don't think you will ever get it to the point of running to cold.

bb69

I ran a C5 auto in my home built car for a couple of years. The weak point is the 3-4 clutch. That is the only failure I had other than the already mentioned overheating and it happened multiple times.

The only other thing to consider is that an auto and a manual do feel different under deceleration and maintenance throttle because they rarely offer any engine braking. It's not a huge difference, but it does change how you handle mid corner adjustments.

Finally, when you add a huge cooler, you need to get the fluid level correct. These transmissions are extremely sensitive to fluid level (either too high or too low). If you get it wrong, the trans life will be severely shortened.

Ken

camcam

What sort of parts did you have in there? And how much power were you putting down?

bb69

The first unit was stock behind a stock 5.3L truck engine making 300HP to the wheels. It let go when I added the Duramax diesel turbo to the car. Horsepower only went up to about 330, but the low RPM torque was greatly increased.

I had that unit rebuilt with all new friction material and a new torque convertor but nothing fancy. It failed in the same way behind a stock 05 LS2.

Ken

camcam

Oh ok thanks, so those were relatively mild builds (if you can even call them that). If I do go through this I would plan on beefing up the trans quite a bit like I mentioned in my first post (billet shafts, sunshell, planetaries, input drum etc.). I have heard good things about the sonnax input drum with bigger 3/4 clutch capacity so that should help the weak spot and everything else is already overkill as I won't be putting nearly that much power as they should be rated for.