rpms rise when clutch is depressed in nuetral
 

So it has been unusually cold here in Portland, OR, lows around 15 and I have noticed that when I start my truck in the morning the rpms sit around 2000 with the clutch in but when I let the clutch out in neutral the rpms drop to about 1600 and the truck moves forward slightly as if it's in gear!

One theory I heard for this is that gears are still moving in thick cold tranny fluid and some of this momentum is actually transferred to the drivetrain when the clutch is out. When the clutch is in the momentum is no longer transferred. Does this sound possible? If so, do I just have to sit there with the clutch in till its warmed up and ready to drive or apply the e-brake so it doesn't start going on its own?

If this doesn't sound right, any other ideas?

Thanks!

Sounds very possible... I'd have to second that. How's it do when warm

When you start your truck on cold mornings, put the t-case in neutral, and the transmission in first, with you e brake engaged. Thus when you are warming up your engine in the morning, you will also be warming up the tranny fluid.

Not sure what's happening with you, you could be right and it's the gear oil. We had -34 celcius today - -46 c with windchill - and I had no issues other than my heater was trying hard to keep up. I used to have a 72 ford 3/4 4x4 that had a similar problem like yours when it got cold, I'd put the transfer case in neutral, put the tranny in gear and let it warm up that way like bone collector said, it works pretty good.

Thanks all, you'll have to excuse my ignorance but how do you put the transfer case in neutral? I only know neutral with the shifter which I assume is the tranny?

answered my own question. The "other" 4wd shifter! Thanks! Also been meaning to change my tranny fluid.

Ok, now I'm confused again. I don't see a neutral position on my 4wd shifter.

2h 4l
] ]
4h - n



2H straight down to 4H right is Neutral then up to 4L

What motor and transmission do you have?

I would have diagrammed it more like:

2H 4L
| N
4H-4H

It doesn't go into neutral just by moving the lever across. You have to move the lever forward again, about halfway to the 4L position.

Correct, neutral (From 2wd) is down, right, then halfway forward.

true, I was trying to figure out how to diagram it. you did a better job

When I had my trans apart (R150) turning the input shaft while in neutral there were gears moving where as the output shaft wasn't. Wouldn't that mean if the truck is running in neutral there are idler gears spinning with the engine circulating the gear oil. I too have had the rpm drop with releasing the clutch. It was the same as just in neutral as it was trans in 1st and t-case in neutral

OK, I will try that. My truck is a 91 V6, I think it has a tranny from a 93.

Yes gears always spin in the transmission with the engine running and clutch engaged .The movement of the engine needs to go some place.

My Tacoma will do the creeping thing even in summer put the case in low range trans in neutral one would almost think it was in gear.

Cold temps just make it more noticeable

That is why in cold temperatures it is best to have the clutch pressed could be the difference between a crank or no crank condition.

Are you running a synthetic fluid? I live 3 hours from Johnny Canuck. Yesterday morning it was -40 before windchill. And my truck wasn't creeping. Its never creeped. I run synthetic fluid in everything. If I don't have synthetic in the tranny, shifting is nearly a 2 hand operation to get the stick to sloooowly move.

Yes in neutral with the engine running and the clutch out there are gears inside the transmission turning. What ever is connected to the input shaft HAS to turn. Selecting neutral does not make the pressure plate not touch the flywheel or somehow cut all power going into the transmission, it simply changes the gear engagement setup inside the transmission to not give the output gear any power.

Without the parking brake on I would imagine it is possible for fluid sheer to cause the output shaft to move a little and this might go away as the fluid warms up and thins a little. It also possible for your truck to just roll away on its own without the parking brake on.

A 400 rpm drop in idle speed (cold) sounds pretty drastic. I do the transfers case neutral and trans in 2nd thing and think it drops about 50rpm, granted I live in SoCal and cold to me 50deg F ;)

My tracker does the same thing until everythings warmed up. I do the neutral trick with the t case and trans in first to warm up everything, otherwise everything is thick and slow to move. my runner has yet to do it tho.