yes, i was speaking about even a built one. 7800 rpm's is pushing it in any 4L60E IMO.

read up? i'm the one that coined the "RPM's being the 4L60E's biggest killer" theory on LS1tech. i've been studying them for a while, too, and while i have no clue on how to build them (although i'd LOVE to learn), i have my own theories about them.

i think it's more a combination of torque at high rpm's than anything else.

 

there was a guy that used to pop in and out of the automatic transmission forum back in the past that would say a stock 4L60E could handle 500 rwhp all day shifting under 5500 rpm's, but a stock one shifting at 6800 rpm's with 350 rwhp wouldn't be able to hold up. very interesting to say the least.

 

I agree with the line pressure as being a big killer 4 transmissions. Increasing line pressure will help with preventing as much clutch slipping. But also increasing line pressure will take out the pump alot sooner than not increasing line pressure. But I rather replace a pump than the whole transmission anyday. So anybody running higher shift points or modding there cars beyond a few simple bolt ons should definitly increase line pressure

 

once again, hp is not the killer. torque is.

a stall usually multiples tq. and that turns in the transmission. all the parts in the transmission turn. there for the force acting on a transmission is torque.

there are parts out there to allow you to spin your transmission and hold up past 6800. and besides im not looking to spin 7800 rpms. im looking for 6800-7100. and at that, im looking to hold something around ~450-470 tq to the ground (stock stall) and putting it with my 4400 tci 2.8 str stall and something around 150 shot of n20 (measured at the ground) without the stall you are looking for something around 500+ ft lbs of tq. and we all know 150 hp of nitrous is more that 150 tq b/c all forced induction adds torque - horse power is a by product that people "can under stand"

 

Guys reality is HP TORQUE and RPM can kill
hp and torque as a combined enity by twisting tearing up hard parts and clutches which is why these are upgraded in Built units ,
RPM though as mentioned Presure loss and resulting clutch slip due to pump slide colapsing pump and additionally loss of lube for the same reason in a poorly prepared or stock pump.
Heat unless very very excessive while a killer to is a minor player in the short term .

Addressing why people dont mention torque in power handling it is subjective .
for instance and engine with 400 ft lbs torque at the crank with a converter that has a 2.0 for instance STR at a given RPM may send 800 ft lbs of torque to the trans for a breif period where as the true torque of the engine is still only 400 ft lbs if measured on the dyno with the lockup clutch applied
Hope this helps wish I had a thread about our transmissions saying good things running this long lol
Perhaps I should rename our sale today as PerformaBuilt One day sale and what kills and trans and what we do to stop it lol

 

I don't want to hear about theories--------I want facts......

 

No Theory in what I wrote Just the facts all these things are killers and with the exception of heat in the right situation they can all kill a trans in and instant

 

are you aware how horsepower is calculated?
horsepower = torque*RPM / 5250
if the horsepower is in the 500's, the torque in a pushrod V8 must be somewhat high also.
i'm still saying that RPM's are a bigger killer to the 4L60E than torque is. 500 ft-lbs of torque at 4,000 RPM's isn't nearly as deadly as 400 ft-lbs of torque at 6500 RPM's.

but not all torque is equal. torque produced down low isn't nearly as deadly as torque produced up high. it's all about where the torque is contained. stock 4L60E's can handle torque down low.

i'm still sticking with the idea that high RPM's are dangerous to any 4L60E, no matter how heavily built. i'm sure it's doable, but it's very difficult. this is why so many 4L60E builds fail.

 

I still don't buy your theory. From everything that I have read the stock 4L60E pump slider spring is designed to handle 5500 to 5700 rpm. Anything over that CAN cause pressure drops. As it has been stated in previous messages---- not one single stock tranny is exactly the same. The tolerances can vary from one to the other, which will explain why some stock trannies take the abuse better than others.

From a mechanical standpoint, there is a remedy to make a 4L60E withstand a certain amount of HP, Torque, and RPM's over factory ratings. What I have read about this slide spring replacement is that there is a spring good for 5500+ rpm. Doesn't elaborate as to how high it is good to, but then again all trannies have different tolerances and thus, will vary. Take this with a grain of salt, but to say that the main killer of a 4L60E or any other type of tranny is RPM's makes you sound mechanically uneducated.

I am everything shy of ASE certified and have enjoyed mechanic work for 12 years. I have rebuilt engines and done from off restorations. I have rebuilt manual trannies, but never automatics. I am crossing all my T's and dotting all of my I's before I start on mine. I will certainly post my results, even if I **** up my rebuild, which will be costly, but I am willing to take my chances b/c I feel that I am capable. The only thing that I am hoping for is a full racing season of mid to high 10 sec 1/4 mile passes out of the tranny that I am building.

 

yes i know how hp is calculated. but going thru a torque converter makes the torque and hp to the ground very different than if it was calculated at the fly wheel. 5250 is the number you use for fly wheel only.

i am automotive tech. i have been doing this for about 10 years. my buddies and i always throw around ideas and theories about car stuff.

but let me guess, you dont build transmissions do you? you are not an engineer are you?

every thing affects the trans. its just not one thing. they all add up. but forget rpms. we can fix that, i wanna know how much tq they will hold. and that should be everyone else question.

 

I understand this statement. It is basically rotational speed.

You have explain this one to me. Torque is a measure of twisting force; 400ft-lbs is 400ft-lbs no matter the rpm.


I just don't see the basis for this conclusion. Your previous statements point to high rpm being the killer, not the level of HP at high rpm being the culprit. There's some data points to support that. The only way to prove this theory would be to take a group of stock cam cars with minimal mods and spin them to 7000 rpm and see if the trannies don't grenade.

 

i actually like your theory of the pump spring. i think that would be a good explanation as to why stock 4L60E's can't handle RPM's over 6,000, even with mild power, but can take a blown setup for a bit with stock shift points.

 

what i mean by this is where your torque is produced. what i'm saying is that a car that produces 350 ft-lbs of torque at 6800 RPM's is more dangerous to a 4L60E than a car that makes 450 ft-lbs of torque at 3,000 RPM's and never sees above stock shift points. even though the 450 ft-lbs of torque car is making an entire 100 ft-lbs of torque more, the fact that it's making it so low in the RPM range isn't hurting the 4L60E as much as the car making less torque way up high in the RPM's.


honestly, i don't know much at all about transmissions. i just know that people start having problems with stock 4L60E's when they change the factory shift points. 4L60E's seem to last a long time when you don't touch the shift points, but when you up them to ~6800 rpm's, it's like the kiss of death.

 

I gotta agree with ChacoTaco on this. It's not really even a theory. Just look at the cars that lose transmissions. Although there are a variety of reasons, the vast majority have one common denominator: high RPMs.

(yes, I'm bringing it back to life)

 

It's not the tranny that is the problem. It's the pump that can't handle the high RPM's. At high RPM's the pump loses pressure. Remedy the pump and spin as many RPM's as you want.

 

but the pump is part of the transmission...so the problem is actually the tranny. what you're saying about fixing the pump and the tranny will spin as many RPM's as you want...that's complete bullshit. yes, there is no doubt that the pump will help, but the question is, how much? another 500 RPM's? the FACT is, even with the most built 4L60E, the higher the RPM's go, the greater the risk of damaging things are. here's what i think:

think of when the 4L60E shifts during WOT. it'll shift from 6,000 RPM's, then go into the next gear at ~4,000 RPM's. it falls ~2,000 RPM's and then slams into gear. well, what happens when you raise the shift points 500 RPM's? the car falls 2,500 RPM's and slams into gear. the gears are being slammed 25% harder just from that 500 RPM increase. raise the shifts to 7,000 RPM's and you increased the stress of every WOT shift 50%. even if we assume the pump is indestructible, you're still slamming the internals a lot harder. this is one of my favorite quotes:

now, some people may be thinking "okay, just throw on a torque converter to raise your shift extensions. then the RPM's won't fall as great during each shift. well, that opens up a whole new can of worms. aftermarket converters have a higher STR and apply even more torque to the transmission. while the shift extension may be better in terms of slamming the planets or any other part, you're still slamming with an even greater torque than stock, so it kind of negates the effect.

now, we also have to mention that the pump still isn't indestructible, and the higher you spin the RPM's, the more pressure is demanded to keep the clutches safe. in real life, the pressure is not exact every time. mechanical parts are prone to error just like humans and the line pressure isn't constant every shift. it's just not possible. all you need is one slip, one slight malfunction, one air bubble in the line, anything - and you have toasted clutches. the fact is, the higher the RPM you go, the bigger the risk of your tranny grenading is. again, 500 ft-lbs of torque being burdened on the transmission at 4,000 RPM's isn't nearly as dangerous as 450 ft-lbs of torque being burdened on the transmission at 6,800 RPM's.

again, i'm not a professional, this is all my theory. i'm a theorist, this is what i do. all i can tell you is, what i'm saying tends to happen. it's a fact that 4L60E's with raised shift points blow up more and faster, even when built.

 

The high STR adds a lot of torque, but it does it when the tranny is operating at low rpm. STR occurs at zero rpm on the converter output shaft which is the input shaft to the tranny. The torque multiplication drops off pretty significantly for most street converters (~3600 stall and lower) by the time the output shaft is up at 3000 rpm. As I understand it, this would be torque at low rpms under your theory.

Attached are graphs I did from data on the SuperYank during a testing program. It's pretty old, but it gives you an idea of torque multiplication curves. BTW, the SY had a long torque multiplication curve for a 3500.

 

I finally got my tranny out and I have started the teardown...... Here are a few interesting pics of carnage:

Input shaft





Sunshell:



I know that there is more damage when I get the rest of it apart.....

If anyone is interested, I can email a copy of my tune. My mods are Hooker LT, ORY, !air, !egr, 4.11 gears, and a 125 hp nitrous shot. Tranny did have billet servos, but problems were there before the servos were installed. Shift points were set 1-2 6000 rpm, 2-3 5900 rpm, 3-4 5900 rpm. I tried lowering the mph to dial in my shift points. The 2-3 shift was a rev limiter banger (6400 rpm). Tranny took a dump on a 20-25 mph roll flooring the gas pedal. With 4.11 gears it was in 4th on the coast and downshifted to 1st and I was surprised with the big BOOM. Put arear on jackstands and ran it through the gears and it returned to drivable (damage was done, things were bent inside). Did the roll punch a couple of weeks later and it did the tranny in to what you see in the pics. Tranny did break all motor on blacktop pavement and didn't hook. Fastest all motor run with stock converter was a 13.02 in the 1/4. 11.73 with a 125 hp shot.

 

so, i've read this whole thread and all i keep seeing is "the stock tranny fries because of power and rpm's". what about the heavily built trannies, such as performabuilt and rossler? can they be spun to 6800 and last? or are they not worth 3k? my car is a 410-420 rwhp forged 347 with a 150-200 shot.

 

Rossler has a proven track record. I'd plan on assuming that a 4l60 subjected to 600 rwhp on a somewhat regular basis will need freshening every year or two.