4t60e horsepower limits

[93CutlassSupreme]

run an additional trans cooler before the trans cooler in the radiator

[gp90se]

run an additional trans cooler before the trans cooler in the radiator

 

why

[93CutlassSupreme]

run an additional trans cooler before the trans cooler in the radiator

 

why

 

 

So you don't overcool the trans fluid.

 

Heat kills transmissions, but the fluid does have to reach a certain temperature for the trans to operate correctly.

 

Ever notice on cold days, if you jump right on the freeway right after startup the trans doesn't shift into overdrive until after a few miles? The fluid needs to warm up.

[gp90se]

reason #1 i posted. I let my cars warm up on cold days so fluids flow like they should, but for anyone who drives there car without warming it up, I agree with you.

[93CutlassSupreme]

reason #1 i posted. I let my cars warm up on cold days so fluids flow like they should, but for anyone who drives there car without warming it up, I agree with you.

 

Trans fluid isn't like engine oil or coolant, it doesn't really warm up until you drive.

 

Obviously you guys can put aux trans coolers wherever you want, but it makes sense to me to put it before the radiator and nowhere else.

[gp90se]

the fluid stays in the radiator long enough that it heats back up to what the engine temp is, defeating the purpose of a cooler.

[timg]

Think about this.

1. Higher shift points = greater dRPM between gears.

2. If two engines have the same torque (say 150 lb-ft everywhere), one shifting at 5252 has 150 hp when shifting. The one shifting at 10504 rpm has 300 hp.

 

Tim

[bartonmd]

Think about this.

1. Higher shift points = greater dRPM between gears.

2. If two engines have the same torque (say 150 lb-ft everywhere), one shifting at 5252 has 150 hp when shifting. The one shifting at 10504 rpm has 300 hp.

 

Tim

 

A tranny doesn't care about HP... Torque is the only thing that's "real" to it...

 

Mike

[timg]

A tranny doesn't care about HP... Torque is the only thing that's "real" to it...

 

Mike

 

I partially agree with you, but I think automatic transmissions are a bit more complex than most in this thread have admitted. I would consider an automatic transmission to be the equivalent of both the clutch/flywheel and the transmission itself of a manual car as it performs the functions of both.

 

Why.

Well, let's start with HP=TQ*RPM/5252 Horsepower and torque are intrinsically related. An engine that has 200 lb-ft of torque and revs to 5000 rpm has 190 hp. One with 200 lb-ft of torque and revs to 10k rpm has 380 hp. The one with 380 hp will destroy the one with 190 hp in a straight line. Faster acceleration = more force at the wheels = more likely to break things. That greater force is most likely due to one of two things:

1. different gearing for the same MPH shift points and hence more torque at the wheels at any given point for the 10k engine.

2. the same gearing and more torque at the wheels on the 10krpm engine after the 5k rpm engine has to shift.

It's definitely more complicated than that though.

 

Then, let's look at a car that shifts at 45 mph from first to second at redline and 75 mph from second to third at redline. If it revs to 10k rpm, there's a 4000 rpm difference between the required rpm in first and second gear at 45 mph. If it only revs to 5k rpm, that difference is cut to 2k rpm. Just like any clutch, the smaller the difference in the speed of the input and output shafts, the less work and wear the clutch has. IE- for a given level of torque, the wear and stress on an automatic transmission change drastically with horsepower and rpm.

 

tim

[timg]

BTW- I'm running a tranny cooler half the size of my radiator with a rebuilt tranny with HD clutches, higher line pressure, a higher stall speed torque converter, and various other mods and it still slips when I shift at 7-9 psi catless. 7 psi and 263 whp (catted) wasn't a problem though.

 

Tim

[bartonmd]

You are correct about the difference in RPM between gears... THis will wear clutches out faster, unless you do something like Ford does (at least you can feel it more on fords) with retarding timing while the shifting is happening... but we're talking about just trannys now... and that's WAAAY complecated for a DIY project...

 

You try using F-type tranny fluid?? Has less lubricity, so the clutches hold better... Or so I'm told...

 

Mike

[z34_nut]

z34_nut, you rebuild that tranny yourself right? Where did you get the better parts?

 

I didn't have time to rebuilt it myself, Our shop was backed up 3 weeks for trannies, and I needed the car to be done in 2 1/2. so I had to send it out. I'll PM you the bill with part numbers for reference.

[93CutlassSupreme]

the fluid stays in the radiator long enough that it heats back up to what the engine temp is, defeating the purpose of a cooler.

 

My coolant sits right around 195-200*. I highly doubt trans fluid at 200* will kill my trans.

[Brian P]

and engine coolant isn't at 195* after it flows thru the radiator

[gp90se]

170 is optimum for a tranny

[manitcor]

interesting post tim

 

so another trans saving measure would be to use closer gears with a higer FDR though of course you start to limit your max speed since youll run out of gear sooner.

[timg]

interesting post tim

 

so another trans saving measure would be to use closer gears with a higer FDR though of course you start to limit your max speed since youll run out of gear sooner.

 

Actually, a FDR with a lower numerical ratio will have less stress overall. It would reduce the amount of torque at the wheels and increase gearing limited top speed.

Gears that are closer to one another should reduce wear on clutches and probably overall stress on the transmission while shifting. Their ratios will have an effect on this though.

 

tim

[19Cutlass94]

z34_nut, you rebuild that tranny yourself right? Where did you get the better parts?

 

I didn't have time to rebuilt it myself, Our shop was backed up 3 weeks for trannies, and I needed the car to be done in 2 1/2. so I had to send it out. I'll PM you the bill with part numbers for reference.

 

Thank you very much!!!

[sdwhite]

My '93 Cutlass Supreme w/mostly stock 3.1 has 197K on it. Has the transmission in question and there's no hint of slipping. All in all, I'm incredibly impressed with this vehicle. GM probably makes the best transmissions in the world, though every now and then there's one to avoid.

[THe_DeTAiL3R]

They're better than Ford and Chrysler.. so I'd agree. The 4T60 in my 88 GP never let me down, and I pounded the shit outta that car.

[gp90se]

the 4t60 in my 89 regal falls out of 2ed gear @20 mph, but it was babied since day 1 (every owner before me was a little old lady).

 

Ive seen 4t60es blow up at 60k and 260k, but yea, ill take a GM FWD over dodge/ford any day of the week

[92pontiac s.e.]

Isn't a 4t60e basicly a 700r-4? And does anyone know if they offer a rebuild kit for the 4t60e?

[gp90se]

yes they have rebuild kits, no other then the fact there both OD trannys, the 700 r4 isnt anything like the 4t60 or 4t60e internally

[digitaloutsider]

A 700R4 is a RWD transmission. I don't believe it even shares anything with the 440T4/4T60.