Hello all Corvette owners. I'm a newbie here. I used to be a member of an other well known Vette-website but the friends of mine recommended this site as a more PRO if I want some serious information. My english may lack a bit but I try to survive.

I own a 1999 model C5 Corvette charged with a 4L60e automatic gearbox and a 3.15 "performance" rear differential. I would like to install a 3.43 gears differential and a bit tighter torque converter.

So my question is that would there be any noticeable difference between the 3.15 and 3.43 gears? Or should I go to the 3.73 gears?

The 3.43 gears diff would be available as an original GM part but the other higher gear differentials are all rebuilt ones from the used cores. And installing the used parts is always a bit questionable.

And my second question is that what kind of a performance TC would you recommen for me to buy? Yank, Vigilante, TCI or Pro Torque? 1800-2200 stall would be all ok to me because I don't do drag racing. Just normal street driving and some quick accelerations every now and then.

All your help will be highly appreciated. Thank you.

Wild Finn

 

My 99 has 3.73 and no issues. I also have a Yank 3800ss and I drive the hiway alot with no issues. Of coarse I drag race too. Dont think u would have a problem with 3.42s either. Converter and gears wake these babies up.

 

If you do a stall don't go with less than a 2800. Keep the STR at 2.0 or less if you are on street tires and it will launch like a champ without changing the gears.

If you are not doing much to the motor (i.e. stock cam) and are staying on street tires, you might find that just the 3.73s without the stall will be enough.

 

I drove Boltons C5 with stock 3.15 once and the car was slow after that he installed 3.42 gears and let me tell you it made a freaking huge diffrence on the street...

You wont regret this mod.

 

My engine is all stock. The Dynatech headers, Borla stinger cat-back and Callaway Honker are all my mods. 367 hp and thats ok for now.

A stall is not the reason for me to consider a performance TC. If I have understood it correctly, the performance torque converters also deliver more engine power to the rear wheels compared to the stock converters. When changing a C5 differential, it's very recommended to install a new TC too because it goes to the same labor prize.

As I don't do the quick stop and go launches, I think that 1800 stall converter would be all ok. I have been thinking of Pro Torque 1800 lock up converter.

Which TC would you prefer if you were me? A lock up TC or non lock up TC?

 

I have a stock 98 coupe that is my daily driver and I have 3.15 gears and a Yank SS3200 TC in it. It works SOOOOO much better than stock. If you are not looking to do alot of drag racing then the 3.15 gear should be fine. The more gear you run, the worse your mpg will be. I still get 28-29 highway mph. You really need to change to the SS3200 TC. It is NOT too loose for what you are doing. Remember to add a good trans cooler up front.

 

I don't do drag racing. Means that you raise your rpm up to 3000 and then loose the brake pedal to make a quick launch. But I do lots of highway accelerations and the overtakings. A good overtaking speed is that what I'm looking for and I think that 3.42 gearing works better for that and still gives affordable mpg.

Is a trans cooler needed for the high stall converters only or is it must for the lower stall converters too?

 

An 1800 stall is about 200 rpm higher than stock and it is a waste of money.

A higher stall is good for three things:
1) Increasing your rpms thereby allowing you to make more power at launch and greatly reduce your 60' time. It can also multiply starting line torque too, but that is a function of STR chosen, not stall speed. On the street, low STR is very helpful unless you have R compound tires.

2) On the upshift, it provides higher rpms and some torque multiplication to help eliminate the dead spot that results from the rpms dropping so low. On the A4, this a most noticeable for the 1-2 shift. With a big stall you can see benefit on the 2-3 shift too.

3) Allows a higher idle speed for a cammed car. You don't want to fight the brakes ever stop if your cam likes a 750 rpm or higher idle speed.

Ok, now let's apply them to your situation:
You're not interested in reason #1 which is the main reason most people get a higher stall. If you were more of a stop light racer, I'd tell you that on street tires, the guy with 2.73s and low STR 3500 stall rules. That's not you, but just adding 3.42s or 3.73s will improve your off-the-line acceleration, should you start moving more in that direction.

Reason #2 sounds like it would be of benefit. However, it takes 2800+ stall speed to really make much of a difference, and an efficient 3500+ higher is best roll racing. I had a Yank 4000 in my 99 Camaro and it was amazing from a roll. My RPMs never dropped below 5200 and the car pulled through the upshifts like crazy.

Reason #3 is not needed now, but if a cam is in your future, that would be reason enough to do one now. Again 1800 isn't going to allow you to raise your idle speed enough to help with even a medium street cam. 2600 is the minimum for that and that assumes you'd stay with a smaller torquey camshaft. Bigger cams will want more stall.

For those reasons I suggest a good 2800+ stall or none at all. No matter what stall you get, it needs to be a lock-up. There's no reason to back to 1960s technology and get a non-lock-up for a mild street car.

 

What speed to you like to run the car up to? 3.73s top out around 125 - 130 mph depending upon where you set your rev limiter. If you stay under that speed, they will be the best option for performance. If you like going 140 mph, stay with the 3.42s as WOT 3-4 upshifts are hard on the tranny. Obviously you have to balance the creature comfort of higher rpms and slightly lower mpg compared to 3.42s.

Absolutely needed for an aftermarket stall.
I'd add a small one on a stock stall if you are road racing.

 

Thanks for your posts. Seems like you have lots of knowledge and experience from these things.

Where would you install the aftermarket trans cooler? What kind of a trans cooler is the original C5 trans cooler or is there one?

The only reason why I consider changing a TC in the first place, is the fact that it could be changed easily with installing a new differential.

As this site is backed by the Corvettecentral, I may put a link to their catalogue. http://www.parts123.com/parts123/yb....rt~A2~cadefibC

Are those TCI converters shown in the link all lock up converters? It says "bolt in without any modifications." They don't mention anything about a new trans cooler. Where could I find an original stock C5 converter? That could be one option too.

 

I certainly see the labor savings of doing a converter at the same time as when you have the pumpkin off. My point is that doing a very small converter isn't going to yield any appreciable benefits and be a waste of money. Just be true to your needs and goals. If you have had the car a while, you probably have a good handle on what you want.

I realize that 2800 sounds big if you are moving up from a big block mind set, but the fastest guys run a 4000 stall on stock cammed LS1. These cars just respond very well to a large stall. The down side can be a loose feeling, that is easily cleaned up with tuning of part throttle shift points, but that may be another expense you weren't planning on.

I'm not a big fan of the TCI converters, you might expand your shopping beyond the link you provided. Yank, Vigilante, Circle D are some brands you might want to look at before buying.
Trans cooling is through the radiator. Typical cooling needs can be met with a small plate type cooler like the B&M supercooler. 16k or 19k GVW is adequate. 16K is definitely plenty for a 3000 stall, especially if you have a 160 T-stat as part of your mods. You can see an example here: http://www.speedinc.com/catagory.cfm...y=Transmission

Huh? That's what you have now unless you changed it out with an aftermarket one.

 

I mean that a stock TC is a moving part of the transmission which needs to be replaced sometimes like any other moving part in the car. It can be replaced with another stock TC. But I think I go to the aftermarket one

 

If you think the lock-up clutch has had it on your converter, then sure, go ahead and replace it. Early on guys were using a stock truck converter, I forgot which one, because it would stall to about 2600.

 

There's nothing wrong with it yet. My C5 has been driven only 67 200 km (42 000 ml) so there shouldn't be anything wrong with a TC with those kilometers. But as said before, TC is very recommended to be replaced with a new one when changing a differential.