Trying to understand my Auto Trans
 

No problems just wanting to understand how it works.


The scenario:
I have a 2SS/RS Automatic.
I'm cruising steadily at 60 mph, tach reads about 1600 rpms.
I step on the accelerator to quickly get up to 70. tach quickly jumps up to near 4000 rpms then settles back down to 1700ish rpms.


I assume that while I'm cruising AFM was active and the automatic was in 6th gear. :iono: Then when accelerating, AFM turned off then on again at cruising (again :iono:). But why the burst in RPMs?


Is the car downshifting to 5th for the speed burst and then back to 6th for the new cruising speed? Or is the rpm burst more of a computer thing to compensate for something?


Thanks for explaining, as I said, I'm just curious and want to understand better about this stuff. Embarrassed to be asking. :facepalm:


:popcorn:

You shouldn't be embarrassed to ask to gain knowledge!

Basically you have it right, in 6th, the AFM may or may not have been active, depending on all the parameters required (speed, gear, RPM have very little if anything to do with it).

When you hit the gas, if it was on, then the AFM turned off (so all cylinders are working again) and based on your RPM, you probably jump down to 4th (maybe even 3rd) gear for a second, until you release.

Then the transmission gear ratio changes back to 6th, and your RPM drops back down. After a bit, if all the parameters are met, AFM would turn back on (so its in V4 mode).

Sometimes while at a steady speed, the RPMs can fluctuate, due to the torque converter locking, releasing, and so forth. When AFM is active (in V4 mode) the RPMs will stay the same as if in V8 mode, since the engine does not change speed.

Call us for the best prices!
- Jeremy :headbang:

Thanks for the reply. I'm glad was somewhat close to having it right. Just wanted to be sure I understand what's happening so that if/when something wrong happens I'll be able to identify it easier and quicker.

As a side question, for those that drive with a manual transmission, is downshifting at high speeds the normal way of getting a quick burst of extra speed? As an example, if you were passing someone?

Yes, when driving a manual you would downshift to "get a quick burst of speed" also with your auto when using tapshift you would manually downshift.

Yes, it'd be pretty much the same as if you drive with your tap shifts, get on the freeway, cruise at around 65 or so, click the right button to go into and stay in 6th gear, then floor the gas. It won't have very much power in that range.

Then you can click the left button to drop you into 5th, and there is more power, same down to 4th.

The tap shift will not allow you to do anything bad.
Thats how manual transmissions do it too; they have little power in 6th gear at normal freeway speeds, they too have to downshift to get power.

- Jeremy

This is great info! I can't wait to get in the car and try out my new learnings. It will make tap shifting more fun, I'm sure.

Yeah, driving with tap shift is really a different animal.
Its fun to drive the car normally, but then if you start to use tap shift all the time, it will be like adding a new performance mod.
However, your gas mileage will go down, since we are not programmed to be the most fuel efficient, like the car's computers are. :D

- Jeremy