4T80E

[JimW]

Recently I have been impressed with my 4T80E. I found out that despite the 24% power lost from the crank to the wheels, the 4T80E is more efficient then the 4T60, 4T65-E and HD with 25% 26% losses.

Lemme explain what happened to me on Friday night, I was comin home from a friends place around 130am. It was dark and the rains had fallen about an hr earlier. The roads were wet, but not soaked.

I accelerated normal out of a stop light, but pushed a bit harder during my 2/3 shifting range. Once the tranny was in 3rd I mashed the gas, my RPM's flew off the handle and I broke traction on the roll during my 3/4 shift, it was amazing. High powerband torque is great!

[Marc]

This is an excellent trans. What I like most about it is
that it has a large oil capacity, 15 quarts total. This is
good for keep the heat down when driving really hard.


_______________

GM!!! BRING BACK OLDS!!!

[JimW]

I hear a lot more stories about the Northstar failing before the trannies on these cars!

Maintain the engine properly and the Aurora has the potential to last as long as its cast iron block cousins.

[Marc]

Those Northstars that blew up were mostly the early
ones...1994 & 1995 vintage. But then again, this was
a totally new design and you always have that happen
with that.
From my experience with American V-8s, which stretches
back over 40 years, I have found that those V-8s will
last practically forever if you change the oil & filter
on a regular & frequent basis. You also have to pay
attention to cooling and tuning.
The Aurora engine will last as long as a cast iron one
as long as those simple rules are followed.

______________

GM!!! BRING BACK OLDS!!!

[JimW]

Good point, I hope that stands true for mine

[Marc]

It will.


_______________

GM!!! BRING BACK OLDS!!!

[tedhontz]

was the 4T80E put in all auroras, even the 95?

[JimW]

Yes. The 4T80-E is found in all Auroras (err Aurori)?

[Marc]

All Aurora 4.0s (1995-2003) have the 4T80E. The Aurora
3.5 (2001-2002) has the 4T65E.


______________

GM!!! BRING BACK OLDS!!!

[tedhontz]

yeah, i meant classics. thanks!

[R4D30N]

would the autobahn to no autobahn have a different model number?

[JimW]

No, only gearing number is different. 3.71 vs 3.48, I've seen both in action and the Autobahn revs higher in general.

[R4D30N]

mine idles at a little bit more then my dads non-autobahn.. but it seems like he gets alot more gas milage.

[JimW]

I want to believe there is minor PCM tweaking to handle the higher revs. Its irresponsible for GM to build a car that revs higher (ie Autobahn) and not customize the computers to handle it.

I still get great mileage...both on city and hwy.

[Aurora40]

JimW said:

I want to believe there is minor PCM tweaking to handle the higher revs. Its irresponsible for GM to build a car that revs higher (ie Autobahn) and not customize the computers to handle it.

I still get great mileage...both on city and hwy.

I don't think the Autobahn car revs higher does it? Both have a cutoff at 6000 rpm, don't they?

[JimW]

Under load the car does rev higher then the non Autobahn version Aurora, however they both have the same rev limiter, 6200 in drive I believe, 4500 in idle? something like that

[Aurora40]

JimW said:

Under load the car does rev higher then the non Autobahn version Aurora, however they both have the same rev limiter, 6200 in drive I believe, 4500 in idle? something like that

Do you mean if I floor it in one, it will rev to say 5900 before the shift, and the other will rev to say 5700 before the shift? Or do you mean that if both are cruising down the road at 70mph, one will be turning a higher rpm than the other?

I know the second is true, but I didn't know it if the first is true. And if it is, how weird...

[JimW]

OK..each gear has a rev limiter, I'm just talking about the OD rev limiter, and its in the low to mid 6K range.

However, if you leave the car in 2nd gear, the tranny WILL shift down to 3rd at 5900, that happens when you do AutoTap runs in 2nd gear. All the major calculations occur when the tranny forces a shift from 2nd to 3rd.

Also, I noticed in Amandas car, when she drives 70mph, her tach reads 2000 RPM, mine reads ~2300.

[Aurora40]

JimW said:

OK..each gear has a rev limiter, I'm just talking about the OD rev limiter, and its in the low to mid 6K range.

However, if you leave the car in 2nd gear, the tranny WILL shift down to 3rd at 5900, that happens when you do AutoTap runs in 2nd gear. All the major calculations occur when the tranny forces a shift from 2nd to 3rd.

Also, I noticed in Amandas car, when she drives 70mph, her tach reads 2000 RPM, mine reads ~2300.

The difference in cruising revs is due to the difference in overall gearing due to the axle ratio, not differences in the tranny or revvability of the engine.

But you lost me on the other part. Neither car will even begin to approach 6k rpm in OD. The car would be going about 180-210 mph according to your rpm/mph description given (though slipping of the torque convertor might mean you'd only be going say 170 mph). And won't both cars do the 2-3 upshift at 5900 rpm when the gear selector is in 2nd? Or does one do it sooner?

It seems strange any sort of revvability would change with either the autobahn or non-autobahn car as both have the same engine and the same power curve. But I'm not really sure what you're trying to say, and on the 2001+ there is no autobahn/non-autobahn so it's cool if I'm not sure what you mean.

[JimW]

Ok, lets simplify things for a moment.

In park. What is the rev limiter on the the classic 4T80E vs the 2001+? 4500 RPM?

What is the rev limiter in each gear while under load (in drive)

1st?
2nd?
3rd?
OD?

For both cars

Now, at 70 mph, my car reads a higher number on the tach then Amandas car. Mine reads 2300 at 70 mph and hers read 2000 at 70mph. I assume that is because the gearing of the transmission is different, 3.71 vs 3.48. Am I wrong in that assumption?

[Aurora40]

JimW said:

Ok, lets simplify things for a moment.

In park. What is the rev limiter on the the classic 4T80E vs the 2001+? 4500 RPM?

I think about 4500 rpm also, but I'm not one to try that as it's not great for the engine. But I thought you were talking autobahn vs non-autobahn, not classic vs new?

What is the rev limiter in each gear while under load (in drive)

1st?
2nd?
3rd?
OD?

For both cars

The rev limiter on my car is always 6500 rpm. However, the transmission will shift the engine before this point. But if you could force the tranny to hold a gear (you could with a Tech-II), at 6500 rpm, the engine management would cut you off. I guess on your car it is 6200 rpm, though I thought it was 6000. Are you saying that the autobahn car will shift closer to the rev limiter than the non-autobahn car will before the transmisison forces a shift?

Now, at 70 mph, my car reads a higher number on the tach then Amandas car. Mine reads 2300 at 70 mph and hers read 2000 at 70mph. I assume that is because the gearing of the transmission is different, 3.71 vs 3.48. Am I wrong in that assumption?

I think we are getting at the same things here, just describing it differently. Yes, while cruising at a given speed, an autobahn car will turn a higher rpm than a non-autobahn car due to the axle ratio.

It sounded to me like what you were initially saying was that the engine is allowed to rev to a higher maximum in an autobahn-equipped car. But the reason for the limiter is that the engine can be damaged at rpms above that point. So a different tranny or axle still won't allow the engine to rev higher. Like the two 4.6's. One has a 3.11 and one a 3.71, but what allows the 300hp version to have a rev limiter at 6700 vs whatever it was in the 275 hp (like 6200 or 6400?) is internal engine differences, not the difference in axle ratios.

[JimW]

:thumbs up:

Sounds like we are on the same page now.

Good information.

[stevensolds]

hmm my 95 manual says not to use 2nd gear when going more than 8mph or the transaxle could be damaged....

also one question, if i put it into 3rd when going down a pretty steep hill, could that damage my transaxle or could it put more stress on it?? i read somewhere not to do that on here and it will last longer so now i waste my brake pads a bit. hell id rather replace $200 brake pads than replace a US $3000 transmission (i hope i dont have to...). Is this tranny built to last?

[Aurora40]

Um, I think 2nd gear can handle more than 8mph...