jalcon

My shifting from 1-3 gear has always sucked. It's gotten alittle "smoother" I guess...and I noticed a funny thing. The RPMS....in 1st gear it'll go up to say 2500 rpms...then shift to third, go to 2000 rpms....but then it goes back down to like 1750 and then cruises on up until 5th gear. Never seen that happen in a car before, and my truck definitely wasn't doing that when it was shifting "rough". When it was shifting "rough", everything appeared normal on the tach. Any one have any insight to this? If I really gun it, it doesn't really do this as much, and appears more normal. Anyway, see vid below.

w00t692

Torque converter strategy. It unlocks to shift, is allowed to slip slightly for a second, then drops rpms again as it locks down and continues on. This is not "acting funny" this is exactly as designed.

jalcon

I see. Thanks. I just can honestly say none of my other vehicles do that, so that's why I asked.

w00t692

Could you estimate the amount of throttle you're giving it? Here's the Torque Converter slip map (it's in output shaft speed) I circled what you're probably feeling.

jalcon

Yeah about half throttle..totally normal driving. I'm not sure how to read that chart but I can tell you this..it ONLY does it from 1-3. Every other year the rpms drop, and go up smooth as I've always seen any tach do.

jalcon

I certainly don't have to be consistent on the throttle..I mean if I'm medium/light throttle it'll do it..(albeit diff rpm numbers), if I'm medium throttle it'll do it..you get the point..

w00t692

Anyways, just review the map to understand what's going on.

Lower numbers = less slip = pulls rpms down after a shift into that gear at that throttle position
higher numbers = more slip = rpms are free to move until locked at a specific OSS speed

Note every gear past 3rd the OSS speeds show that the Converter will be locked up and you won't get rpm fluctuations as the transmission will drive at the same speed as the engine so to speak.

jalcon

Alright....Well..like I said if I give it decent amount of gas, and run it harder...say shift at 4k...I notice no slip. I also don't notice the slip if I'm in a parking lot barely giving it gas. It's normal driving when I see it.

jalcon

Also don't see it in sport mode when the truck actually goes 1 - 2 - 3 gear.

w00t692

You don't see it in sport mode because in sport mode it doesn't skip shift so the rpm difference between 2nd and 3rd is way less than the one between 1st and 3rd. So the skip shift pulls the rpms down where they actually are after the shift while in sport mode it's so minor you don't notice it.