GMC Truck Forum banner

1 - 8 of 8 Posts

·
Premium Member
Joined
·
10 Posts
Discussion Starter #1
I attached an article I read this week on Torque Convertors. Please read and tell me what you think. I'm thinking about a Torque convertor from Circle D (GM 278mm HP4L60E. Modes to go with 212/218 Cam, Pacesetter Long tube (No cats) Under pulley. I already have a NP Tune. Cold Intake, Corv. Servo,Trans-go Shift kit. This is a 6In lifted truck with 35in tires and 4.56 Gears. I"m not going to the race track. It is used for hunting. I really don't need take off power for what I use it for. I don't want to loose my low end. It is a 2004 Siverado 5.3. Here is the article.

Now the reason to change the stall is this. If you have lager than stock cam in your engine or have done other modifications to it, the torque curve changes, and when you launch the car (DRAG RACING) you want the motor to be near peak torque of the curve. One on 4X4 this dose not apply, unless you are doing sand drags or timed mud runs with a very high performance engine. Otherwise Do NOT go with a higher "stall" converter than comes factory.
Here is why. there are two types of stall. Brake stall, which I describe as a flash stall, which is the instantaneous stall if you are sitting idling and punch the gas. It is typically higher than the brake stall by a few hundred RPM. Now, a higher stall also means higher engagement RPM for the converter, Typically a motor idling at 1000 RPM will pull against the brakes. Causing you to need to hold the brake at a light or stop sign. The stall of a factory converter, is a V-8 is typically 1200-1400 RPM. Now if you increase the stall of the converter to lets say 3500, which is really high on anything except a drag car. You could sit at a light idling at 1000 RPM with your foot off the brake and not move a bit. In fact you would not experience any movement of the truck until about 2000 RPM and that would be very abrupt (read in the manual car with a clutch reving up to 2000 RPM and dumping the clutch. As you can imagine, this will tear the drive line up in short order, twist axles. all sorts of bad stuff, so don't do it.
If you are really into truck performance, and want to make your truck run better, by a RV cam for your truck, install a mild shift kit. By this I mean it will increase the harshness of the shift, making it happen quicker (factory trannys are set to slip between gears, this smooths the ride out but will also decrease the tranny life. but you do NOT want to modify the shift points. But this I mean the RPM at witch the truck shifts gears, tire chirp is for cars, not trucks, that is how cars chirp the tires from gear to gear, hard shifts at much higher RPM. Trucks don"t need that, especially if you are pulling things with your truck....
 

·
Left Jizz
Joined
·
1,225 Posts
Stick with a factory or slightly lower stall IMO. Unless you're running WOT all the time, you'll get annoyed with a higher stall converter.
I know even a 400 RPM difference on mine made it more annoying especially when trying to crawl and not fuck up my truck any more than it is already. Although I didn't notice any difference in mud and on the street it's still slow.
 

·
GMFS Member
Joined
·
4,390 Posts
:roflmao:

Who wrote this "article"?
 

·
Registered
Joined
·
4,161 Posts
So you already have 4.56 gear and 35" tire? If so, how do you like the dynamics of the vehicle as is? Do you feel you're not in the powerband as much as you need to be?

A low duration cam like the one you mentioned isn't going to peak very high, and you don't always need a higher stalling converter if you're geared adequately for what you want the vehicle to do and if it already matches the powerband of your engine.

I will say that the circle d 278 is a really easy converter to drive on the street, only flashes high when you want it, and the shift extensions are really nice.

If you're unsure, install the cam and see how the vehicle drives. With 4.56 you might not even need it, and if you feel you do you can always buy it that same day and have it within a week.
 

·
Registered
Joined
·
1,292 Posts
The 1st post is full of inacuracies. 3500rpm is not that high of a stall speed. It may been in a world of 3 speed autos that didnt have TCC's(torque converter clutches).
If you have a 3500 rpm stall, the truck may not move on a slight hill without throttle, but as you apply throttle the truck will simply pull away, there wontr be any jerking. It will pull away smoothly.

I run the factory L35 V6 TC behind my stock longblock Vortec 350 andI get about 2700-2800 rpm. I can apply the e-brake and the service brake on hard, shift into gear and apply WOT and thetach reads around 27090-2800rpm. I am running a stock cam and even on a GEN 1E 350 with superior off idle torque than an LM7 5.3 I noticed much better launching and shift extension reductions. Plus as soon the TCC locks, it drives exactly like a stock truck does.
The L35 behind an L31 350 is just like taking a Trailblazer 4.2l inline 6 cylinder and stuffing the I-6 TC behind a 5.3 or 6.0.
The torque peak of an L31 is 2800rpm.
The torque peak of an LM7 is 4000rpm.
For max acceleration (like drag racing-or street racing-or simply wanting the most push your back into the seat-traction provided) your TC stall should match your torque peak.
I recommend for most street applications that a stall speed about 500rpm below your torque peak be selected.

Stall speed is very akin to the clutch of a snowmobile if that helps anyone.

Even in my truck I would like a nice 3200-3600 stall, and thats with my stock cam 191º/196º 0.412"/.428" on a 111ºLSA.

If towing any substantial weight stay under 3000.

An RV cam will get you nothing but disappointment. RV cam means off idle torque with zero hp gain, also known as a stock like cam. It all depends what you use your truck for
but this is an Engine/Performance forum.
The V6/Inline 6 TC's are good choices for those that arent sure about TC choices. Quality performance tC's arent cheap, you pay for what you get. A nice 3200rpm performance torque converter makes a stock 5.3 truck wake right up, from doggy from a stop to actually working well. IMO these 5.3's should have more TC from the factory.

peace
Hog
 

·
Premium Member
Joined
·
10 Posts
Discussion Starter #7
Could not find sorce of article.
So you already have 4.56 gear and 35" tire? YES
If so, how do you like the dynamics of the vehicle as is? It is very close to how I want it. It got a little doggy going down the minimum B roads last winter after the snow melt.
Do you feel you're not in the powerband as much as you need to be? I think a little more power on the bottom will help. Some of the issue is the soil in Nebraska is a clay/mud combo. I have Dick Cepek Mud Country Tires they clean out very will. They at times fill up.
Game Plan. Do the (Cam,Headers,Re-Tune Fron NP) see how it reacts this Winter/Spring Hunting Season. Thank You help and interest.
The article is very interesting.
 
1 - 8 of 8 Posts
Top