Converter question

[VinPecora]

I plan on rebuilding my moter and trans this year. I have a 20g with minor boltons, ultimate ect....I was planning on forged .30 over, comp cam, and vortech heads, what type of converter should I use with my trans rebuild? I was thinking 2400-2600 stall but i dont know what size or lockup to get....or even the prefered brands and where to buy.

Please help me out here!

 

[Vertigo]

Re: Converter question

I'm going to tag onto your thread here because I'd like to know something similar. I'm also just about to bolt a 14cm 20g onto our Ty but the internals are staying stock for now. I was contemplating a 2800 stall until a mechanic friend of mine reminded me that you don't want to be running around the majority of time under stall speed.

What would we have to watch out for or do so that these transmissions don't cook? Can we just use a large trans cooler or is it a better idea to pick the smallest stall needed? For what it's worth, I'd stay with the stock stall speed and sacrifice the hole shots for the power up top anyway.

 

[VinPecora]

Re: Converter question

i have a cooler and deep pan so i should be ok, i had a 2400 on my last truck and the trans ran hot! I just dont remember if it was a 9-11 or another size....truth...i dont know the differencve thats why im asking.

 

[nallj92]

Re: Converter question

i ran a 2800 lock up with a 20g, worked great, could hardly tell it has a stall, since then i went to a 3100 and a pt63e

 

[VinPecora]

Re: Converter question

what kind of 2800 stall?

 

[12secondSY]

Re: Converter question

I'm running a precision industries 2800 stall. I have a stock turbo with a 20G wheel, vortecs, 415 cam and so on. Heres where I bought mine... http://www.raceprovenmotors.com/cart/product_info.php?cPath=48_102&products_id=111

I'll let you know how it does here in the next few weeks soon as I get the truck back out.

 

[George Blake]

Re: Converter question

I know it's expensive but what people need to do instead of saying, "I have X turbo what stall do I need?", people should go get a dyno test of the truck all the way through the full rpm range that the engine is built for using the max boost you plan on running. What this does is gives max torque and HP and what rpm they occurred at. Normally max HP and Max RPM are at much different points in the rpm band. Also, when the converters are set up, the stall speed you are asking for may not be the stall speed you need. And the converter manufacturers I use have told me that the stall the person is requesting is way out of wack from what their engine wants. So your converter is not just specific to the turbo. It will vary from truck to truck, cam, turbo, heads all of that varies. And the bad part is, you can have the same turbo, heads, cam as the truck next to you, but with a crappy tune, they won't be ANYTHING alike. I keep dyno sheets from all customers who use me and I use them as a base line but I still try to get guys to take the truck in for a dyno test when they are doing something out of the box.
I'm currently working with a manufacturer to get the switch pitch type characteristics of the 4L80e converters with massive lockup into the 4L60/e design. I'm hoping to have an answer this week or next. This will help significantly with guys that really need 3400 stall for crunch time but want 2000 rpm for daily driving out of the same converter.
Whoever you use, just try to keep this info in mind when selecting your stall.

 

[Vertigo]

Re: Converter question

I think I get it now. The lockup will prevent the truck from being under stall speed and burning out the trans.

So if I was thinking that to match a stall with my truck I'd see at what RPM the turbo begins to build boost would be flawed logic? Now that I think about it, I see how checking the torque/hp curves makes sense.

 

[gjp]

Re: Converter question

George is building a 80e trans and converter for me. I was surprised when he asked for my mods, not just the turbo. He wanted truck weight too.

 

[George Blake]

Re: Converter question

Lockup has nothing to do with the way the stall behaves. Lockup is not set to happen until 70mph at WOT in the stock ecm. When you take off in first, there is no lockup. Physically impossible. No oil goes into the lockup circuit until you reach 2nd gear. Stall is most apparent from a stop. The stall will basically let the converter slip a little until the torque put through it matches and multiplication increases until you lockup the converter. The halves inside the converter will slip until you lock up it up. Lockup locks those halves together. So now the crank is physically coupled to the input shaft of the trans.

In order to do a stall, you need:
Weight
Engine displacement
Max HP and what RPM
Max Torque and what RPM
Gear ratio in rear end
Tire height from ground to top of tire
Max rpm the engine will be run at
Type of flywheel (LT1 vs LS1)

If you don't have a dyno ADD:
turbo
heads
cam
Max boost
Max boost at launch
Nitrous, what shot?

This is why a converter set up for 2600 stall in one guys truck that you buy used and then stalls at 3400 stall in your truck can happen. He didn't lie, it's not set up for your truck.

I think I get it now. The lockup will prevent the truck from being under stall speed and burning out the trans.

So if I was thinking that to match a stall with my truck I'd see at what RPM the turbo begins to build boost would be flawed logic? Now that I think about it, I see how checking the torque/hp curves makes sense.

 

[Vertigo]

Re: Converter question

Perfect, thanks for the info! So there's no ill-effects from a higher stall (effective stall speed of say, 2800rpm) since the ECU will lock up the convertor at cruising speed on the highway.

 

[George Blake]

Re: Converter question

Yes. There are ill effects. I don't know if you understand what I'm saying.

If you get a true 2800 stall matched to YOUR engine, you'll be ok.
If you just get a "2800 stall" and you don't get it matched to YOUR engine, it may stall at 3500 rpm. In that case, it'll be a flat dog leaving a stop light, pulling speed bumps and driving through parking garages and parking lots. It will also run VERY hot. That means very short trans life.
What you can do, if the trans is running hot is lock up the converter to prevent the halves from slipping and generating heat...either that or just pull over. The 700 has very small clutches and runs hot anyway.Your best bet would be to dyno your truck. If you have a stock converter, it is set up to stall with a stock engine at 2075 rpm. Give all of this info to the converter manufacturer and they can make one that you need. You may not need 2800 rpm stall. You made just need a 2400 or 2500, or 2600.
2800 rpm is kind of a "generic" catch all because the rule of thumb is that you do NOT want a converter in a street vehicle that stalls higher than 2800 due to driveability. So, that is what everyone uses. Until now with the 4l80e because I can now get a very nice converter that behaves like a 2000 stall until you get into it, and then it behaves like a 3200, 3400, whatever you wanted it to do....but you gotta have dyno sheets to be accurate.

 

[Vertigo]

Re: Converter question

You can boot me in the nards if what I'm about to say has been covered, therefore I obviously don't understand

My initial worry was that on a long drive, at 2200rpm cruising, a "2800" stall might heat up the trans too much. But how I now understand it is that since the trans will be in lock-up at that point, I might be worrying over nothing.

I can totally see how a stall that's too high would be a dog, as well as one too low. I'm also really happy there are two AWD dyno's nearby (yes!) so getting the proper graphs will be beneficial.

Thanks again for your time, George!

 

[TYTILIDIE]

Re: Converter question

I bought a 2500 stall convertor from our local convertor shop. On DM, I was launching at 28-3000 RPM. I verified this by looking at the tach. George is right. FWIW, I had the 2500 and I thought it was awsome, I had great spool up and everything. A friend of mine has an almost identical set up and he had a 2800 and his ran just like mine. I now have a 3000 stall and it is exactly the same as the 2500 I had. Its wierd stuff for sure.

 

[jwaller]

Re: Converter question

You can boot me in the nards if what I'm about to say has been covered, therefore I obviously don't understand

My initial worry was that on a long drive, at 2200rpm cruising, a "2800" stall might heat up the trans too much. But how I now understand it is that since the trans will be in lock-up at that point, I might be worrying over nothing.

I can totally see how a stall that's too high would be a dog, as well as one too low. I'm also really happy there are two AWD dyno's nearby (yes!) so getting the proper graphs will be beneficial.

Thanks again for your time, George!

On a long drive you dont need to worry about a stall thats too high bc your going to have the converter locked up and not slipping. unless you buy a non lockup which is the wrong idea.

The problem with high stall converters is the around town driving. too much slip = a ton of heat that you may not be able to disapate with your cooler setup and it may drive like a dog.

 

[tyndago]

Re: Converter question

You just drive around town at full throttle all the time. No problem.

I was running a 3600 stall on my stock turbo, full weight Sy. It was a little on the loose side

 

[midnightbluS10]

Re: Converter question

You just drive around town at full throttle all the time. No problem.

I was running a 3600 stall on my stock turbo, full weight Sy. It was a little on the loose side

 

[George Blake]

Re: Converter question

You just drive around town at full throttle all the time. No problem.

I was running a 3600 stall on my stock turbo, full weight Sy. It was a little on the loose side

3600 on a stock turbo? Who the heck talked you into that?

 

[tyndago]

Re: Converter question

3600 on a stock turbo? Who the heck talked you into that?

3600 on a stock turbo is what happens when you have 3 trucks, not much time, not much money.

The Ty had a 63 mm turbo on it, KB 9/11(thats how long ago I bought it), and a semi-built trans. The truck was stolen and returned, the engine was hurt a bit on an 11.85 pass, and I got kicked out of the track. Parked it for a while.

The Sy I managed to break a couple of trannys. I eventually ended up with the Ty converter and tranny in it. I hurt the motor, built up a motor for it. Was just running stock turbo, on a good bottom, eventually planning on putting a big turbo on it. Never made it before I killed another tranny.

Eventually I'll get another trans and a more realistic converter to go along with it. Although 3600 sounds like a good start, these things don't rev like GT-R's though.