dwichman

I've had my '01 4Runner 4x4 for over 10 years and have just noticed some strange (new) transmission kickdown behavior when climbing a grade.

My 4Runner has always had what I'll refer to as the "magic gear" kickdown between OD and 3rd, almost seems like the torque converter (or something) slips a bit to allow the RPMs to come up a bit (~500-800 RPM) before it kicks down to 3rd. I'm not sure what part of the transmission allows this to happen, and couldn't find much info searching the forums. Often times this magic gear is enough to hold my speed on a grade before I have to give some more throttle or turn off OD to kick it down to 3rd.

I've never encountered another transmission that does this, but hopefully y'all know what I'm talking about.

Recently the magic gear kick down has started behaving strange. Allow me to explain - as I approach the base of a grade and my speed begins to reduce I give the throttle a blip-and-hold to kick down to magic gear. Then I'll hold the throttle steady and if so long as the speed holds steady and I don't depress it further it will stay in magic gear until I reach the top of the grade and roll off the throttle. Just recently however it will only hold the magic gear for about 10-20 seconds, at which point it will "shift" back into OD and the RPMs will drop about 500-800 resulting in a reduction in power and speed. I have to depress the pedal further and at some point it kicks down to 3rd.

Furthermore when it comes back to OD after the magic gear as explained above, if I instead back off the throttle and give it another blip-and-hold it will go back into magic gear, but for a shorter amount of time (2-5 seconds maybe) before it drops back into OD.

The truck has 150K and has had routine tranny flushes with Dextron III, at least 2 I believe, with one recently in the last 20K. I checked the tranny fluid while hot and it was a quart down; added a quart and it made no difference. I do not have strawberry milkshake based on looking in coolant reservoir, radiator cap and tranny dipstick (nice and red fresh fluid).

I'd greatly appreciate if someone could explain this "magic gear" to me, and any ideas on why it is no longer holding.

millball

I believe that your 'magic gear' is the torque converter coming out of lockup.

When the converter is locked up, the tranny acts as a manual transmission does, that is, there is no hydraulic slip. This gives greatest fuel economy. The engine thru to the rear end has a solid mechanical coupling then. Lock-up is usually when cruising in overdrive. I don't know if the converter will lock up in lower gears, I don't think so. Maybe someone else knows otherwise.
When it comes out of lockup, the engine revs a bit higher and the converter gives a hydraulic coupling instead of a solid connection. These higher revs give a bit more power.
When more throttle is given, at some point the tranny will drop into a lower gear.

I am not too familiar with the newer model trannys, but suffice it to say that the tranny and torque converter respond to a number of different control input sensors that include engine speed, vehicle speed, throttle position, probably converter turbine speed, ect, ect.

There is likely one or more tranny inputs that have changed values over time and the conditions that permit converter lock and unlock have changed because of it.

Has it set any codes??

dwichman

No CEL. I haven't plugged a code reader in for a while. Would it throw a code w/out CEL?

millball

It might. Can't hurt to look.

aowRS

I've wondered about the "magic gear" sensation for almost 14 years and 328,000 miles on my 2001. When it happens, I've always found myself thinking, "but it's a 4-speed, right?".

Curious to see what you find out.



Andreas

vasinvictor

iTrader: (3)

It's your converter locking and unlocking. To test you can be cruising highway speeds and very lightly tap the brake. The converter will unlock and your RPM will rise a few hundred, and then re-lock, all while maintaining the same speed. No magic there, just a function most casuals are not observant of.

dwichman

No codes.

I've also recently noticed light to moderate surging and some power loss when I'm climbing a grade in 3rd. It seems the more throttle I give the stronger the surge, and at WOT it feels like it may be coming back up to full power. Doesn't feel like misfiring, but rather a smoother Air/Fuel related surge to me.

I don't think it's related to my torque converter lock/unlock issue as it is, but who knows?

The truck has never had the MAF or throttle body cleaned in 150K, plug wires are original, fuel filter probably has 70K, plugs 60K+. I ordered all that stuff and will work on it this weekend and report back if there's any change.

I also ordered a Koyorad A1998 for strawberry milkshake prevention since I know all about that now after scouring the forums. Should keep me busy!

Thanks.