The 80e swap is finally complete. It feels really strong. I was rolling down the highway at about 65 and punched it. It used to shift into 3rd at 85 mph now it is shifting at 90mph and when it does it barks the tires!

I took it to the track last night and I was a little disappointed. I lost 2 mph and couldn't do any better than an 8.60 at 80 mph.

I think I need to get some steeper gears in the rear end. What are you guys with 80e's running in the rear end? I currently have 3.73's and am thinking about going to 4.10's.

Then it is time for the heads and cam to make up for those 2mph I lost and then some!

 

The 80 has more drivetrain loss... but it's okay because you can now throw more horsepower at it

 

why did you switch to the 80e. was it b/c the 60e or 65e blew?

 

Go with 4.10s to make up the loss the 4L80E takes away compared to the 4L60E. I would like to know why did GM put a 2.70 first gear in the 80E and 3.06 in the 60E, you would think the 80E tranny would get 3.06 for towing.

 

There are real reasons for this.

The 4L80-E has first and second gear ratios the same as a TH400. First is 2.48:1 and second is 1.48:1 These two transmission share design and a few components, the 80 just has the additional planetary for overdrive and an electronic valvebody.

One reason for the short gears is to make the ratios closer. Closer gear ratios means the clutches don't have to make up as much RPM difference dropping engine speed with engagement of the next gear. With less rpm drop from one shift to another any given clutch pack will be able to transfer more torque at the desired shoft smoothness without overheating.

Another reason is that the TH400 was originally designed for truck duty. These trucks had low-reving big blocks making a lot of torque. These engines had very low redlines. Later the Diesel engine become available. Those engines have an even narrowor RPM range than the bigblocks making the TH400 ratios a perfect match for it.

Finally, a shorter first gear helps preserve drivetrain life by reducing the amount of torque those components could experience. The deeper the first gear ratio is the more torque multiplication you can get. At some point there has to be a practical limit established for how large of a rear end would have to be installed into a truck to survive worst-case torque scenarios.

 

You could get the conversion that changes it from the 2.48 ratio to a little bit over 3 that would make a big difference.

 

Yeah I blew the 60. At least it didnt have reverse anymore.

So 4.10's would probably be my best bet with the 80?