D21 downshifts too often

[Tommywalton]

I'll try to post this as best I can
I have a 1992 hardbody 4x4 se v6 auto.

When at highway speed without cruise around 60-70 mph if I decrease the throttle slightly the transmission downshifts. Which is terribly wrong. If I give it just a little gas it shifts back to overdrive.

When the cruise is engaged if the road goes from flat to a slight decline it also downshifts.

The truck basically shifts up and down constantly at hwy speed only, any help is appreciated

[Rev_D21]

Has it always done this or is this a recent problem? Can you tell us what the axle code on the door jamb sticker says? Do you drive in mostly hilly areas?

[Tommywalton]

Thanks for the quick reply
Hg43 axle code. It has LSD. I assume limited slip diff. Sticker on the diff housing. I just got it so it's always done it. It feels like an error in throttle position relative to speed. The transmission had new oil in it. But you know how that goes...

I live in Mississippi delta so I've only driven on very long flat highways. And off road all is well. I guess at a certain speed this happens but I haven't isolated exactly what speed.

Also the previous owner said he thinks the trans may have been rebuilt. Have no clue.

[Tommywalton]

Also the truck is all stock with factory sized a/t tires. Nothing added anywhere on truck. Everything works too. Cruise, ac everything. The od button also works like it should. The auto/power switch on the dash near the right side seems to work also. The only issue I've noticed is the thermostat is stuck open I'm sure. It barely moves from the left. The engine is very cool running. Barely warm on a cold day so that's one thing I'm about to fix.

[Rev_D21]

Have you checked the transmission fluid color and level?

[Tommywalton]

Yes the level is fine. I can't recall the color but I will check again. It was translucent. I will check.

How does this transmission know when to shift to overdrive? It has a button so I assume it's electrical? If the transmission is good mechanically could someone explain what controls the overdrive? I mean overdrive does work as long as I keep the throttle down. Say 10 percent and above. If I decrease throttle position to lower than 10 percent it downshifts. Almost like it's confused about the speed. Like it thinks it's going slower than it is. If it could think that is.

[Rev_D21]

Overdrive is a combination of road speed and throttle position. There is a kickdown cable that is adjustable that is attached to the throttle linkage at the throttle body. If that is damaged it could be causing your issues. The other one is the torque converter is not locking up properly or not staying locked up when it should be.

[Tommywalton]

I've been reading and was wondering about the converter lockup. It acts almost exactly like some newer trucks in tow/haul mode. And it's sensitive to engine load. I figured this out yesterday. If going up a slight incline it will never kick out of overdrive. Lift your foot or go down a sight grade, it kicks down. Like almost in noticeable downhill grade. Also it functions right if it has a light trailer. Any small load on the engine

[Tommywalton]

I don't see any kick down cable on my truck. The two cables on the throttle body bell crank go to a cruise control and the other to the gas pedal. Where is this cable your talking about?

[Tommywalton]

I saw somewhere during my endless hours of searching other places that if nissan owners complain of excessive downshifting or in and out of overdrive nissan has a service bulletin. Do any of you know of this bulletin? Where is it and how do I find it. I'm going to blow my damn engine up downshifting at 65-70 mph. Anybody?

[lillyputtt12]

Ya Friend,The D21 downshifts is now not coming is good condition.It has many problem with it.So check and get suggestions form other forum members.I am suggesting only for this.
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[Tommywalton]

Are you kidding me? Is that a joke? Wtf would I want to see a can of s*** spam for? Or is that an automatic thing the site does when you try to add a external link to a post? You guys are supposed to be nissan gurus and frankly I'm getting little to no help. Obviously this is a pretty common issue with these automatics.

I've seen the issue on the Internet but came here for a straight answer and have got absolutely nothing but a link to a spam site. The garbage bs salty processed meat spam too.

I'm keeping the thread at the top of the list on purpose hoping someone will see it and help me.