Question about overdrive transmissions..

[VR3]

Yeah...

I was driving today, and when the truck would shift into 3rd gear (I presume) it would drop back into an overdrive, all that - anyways, when I got up to about 35, the truck would get louder, as the RPM went up, then to 45 - the truck still hasnt shifted gears, at about 50 it shifts, but - when it gets to 35, if I let up on the gas - it shifts gears immediately... what is the best course of action - obviously when I let up, the truck is going to shift gears, so when is the best time to do this?

The guy we bought the truck from said it shifted weird when put in overdrive... is this normal for all overdrive vehicles, Ford? etc.. yeah...

[brettw22]

If it's sticking and holding it's gears too long, that to me sounds like a potential transmission rebuild. I don't know if your overdrive is a button push or if you have 1, 2, 3, 4, d (with circle around it to indicate OD). If you have the latter, and you have it in 4 (or 3 if that's as high as it goes) it should shift up through that and be find until you pop it into OD. If you keep it in the OD position and it shifts 1, 2, 3, 4(if you have it), then holds and stick at OD that would be a problem. That would be the way to determine which transfer point you're having an issue with, but be prepped to put your stereo system on hold.

[MacLeod]

Wait til Vinny gets on here. He'll clear this up for ya.

[VR3]

Its a D with a circle around it...

It dosnt "stick" it dosnt like REV to really high RPMs...

It seems normal shifting at the point it does, but the fact it shifts when I let up off the gas is odd...?

[MacLeod]

Its not supposed to rev to high RPM's

[audiobliss]

My dad's International work truck does this. And no, it ain't ok.

[VR3]

Its not supposed to rev to high RPM's

And it dosnt...

[MacLeod]

So whats the problem?

[VR3]

Ok...

itll shift into what I presume is 2nd gear...

Once it gets to 35, it starts to get louder... at about 45-50 it gets to the point where its supposed to shift (it does) - buuuuuuuuuut, if I am at 35-40, and I let up off the gas it shifts early...is this normal?

[MacLeod]

Yes. It doesnt shift according to speed alone, it also depends on throttle level as well. If you were to mash the gas down harder, it wouldnt shift until later because it works as if it were under a load and needed to be in a lower gear. If you let off the gas it works as if its not under a load and can operate at a higher gear.

[VR3]

Hmm...

It seems to be operating normal, Im just 1) not use to driving a vehicle thats loud, 2) a rough riding vehicle 3) driving a vehicle with the power it has...

So it is very ODD...

Getting use to driving a Ford F150 after driving a Toyota Corolla for a year is a weird experience...best I can describe it.

[MacLeod]

Yes, its going to be much different.

Also, that truck is probably older than the car your used to and not quite as plush so a lot of normal vibrations and noises will seep thru into the interior and although youre not used to hearing them, that doesnt automatically mean theyre bad.

[VR3]

Yeah... it will be an experience, hopefully more good than bad.

I dont think its bad, because my grandpaw drove it several times before I did and if there was a problem in that area, I dont think he wouldnt point it out or miss it...hes been around cars for the past 40-50 years probally... lol

Thanks for the help.

[audiobliss]

Well, if it's just happening as Mac described, that's fine. That's how it's supposed to do. It shifts based on speed, rpm, load, throttle input, etc.

Dad's truck I mentioned is just all messed up. I've forgotten the exact numbers, but I'll just make 'em up so as to get the point across. lol Starting off in first it won't shift until about 30 or so (again, I'm guessing) UNLESS he totally gets off the throttle. It's that way for all the gears. No matter how light he is on the gas, if he's pressing it, it won't shift until it redlines. He has to let off the gas completely to make it shift. And that's not normal.

But if it's just doing what Mac described, that's normal.

Oh, and please don't say "it gets louder." That just sounds SOO ignorant. If you mean the engine keeps spinning faster, the rpms get higher, w/e, then say that. And actual rpm numbers would be nice.

[VR3]

I am very ignorant when it comes to cars. What can I say...

It dosnt red line or anything - Ill make note of where it shifts tommorow when I go to HD and other random places...

[audiobliss]

That'd be nice. But it sounds like it's probably just fine. We'll hope so.

[MacLeod]

Vinny knows about 1,000,000 times more than I do about this stuff so he'll straighten this out whenever he sobers up.....er...I mean checks in.

[VR3]

It shifts at 50 MPH at 2 RPM, then it moves back down to 1 RPM

[bobman1235]

It shifts at 50 MPH at 2 RPM, then it moves back down to 1 RPM

Whoa, 1RPM! That's some high-torque engine :)

[HiPerf360]

Thoes RPM are in 1000's,

What you are expirencing is probably the torque converter locking up in third gear under light load. This is normal as it will also do this in 4th gear (overdrive).

If you think that you are still having troubles with it you can call me when you are driving it so i can have a better understanding of what is going on.

What year is the truck? 2wd or 4wd?

Need this info to find out what transmission is in it.

[VR3]

1991 F150 Lariat, 2wd

I think its running fine, Im just getting accustomed to it.

[Red230SX]

In my experiance with trucks that have two speed torque converters what you are
experiancing is what we all bitch about... It switches back and fourth between OD and
D (all done by a clutch inside the torque converter) and sometimes some trucks, like
Fords and older Dodges do it for no reason... My new Ram does not do it... But my
last Dakota did it at will...

If you can disable the two speed torque converter via a button on the dash or on the
shift stalk or somewhere in there.. Try it.. See what it does... Bet it seems "normal"
to you then :)

I can't imagine driving one of those vehicles with CVT Transmissions, it's like a Snowmobile,
no gears..... That has to be an odd feeling, never shifting any gears at all! :)

[audiobliss]

Hmm. A two-speed torque converter? I've never heard of one of those. I thought I torque converter just locked the ratio from flywheel to tranny to 1:1. What does the second speed do? Something like 0.84:1?

[HiPerf360]

There are no two speed torque converters, they just lock up to reduce transmission heat and improve fuel economy.

DO NOT DISABLE THE LOCK UP FEATURE OF YOUR TQ!!!!

At highway speeds with the tranny in OD the speed difference between the input shaft of the tranny and the engine speed are very close to each other. This causes the fluid in the converter to get EXTREEMLY HOT and will overheat your tranny and cause severe damage to the TQ.

[Red230SX]

Audiobliss,

Sorry that was a typo in my part I meant to say "Lockup" :)

HiPerf,

How does a Lockup converter drop engine RPM when it enguages and why does every
manufacturer specifically state when towing the lockup should NEVER be enguaged.

Thoughts?

(I do not profess to being an automatic transmission expert.. I can build a full blown
race motor, I know how to flow bench, balance, CC, Degree and everything inbetween
but the Auto Tranny to me is still something that works on magic pixie dust!)

[audiobliss]

As far as I know (which, mind you, is not much), the torque converter is purely an automatic thing. I'm not aware of the ability to 'disable' it.

How does the lockup torque converter drop engine RPM? I was going to answer that, but I've sensed that you're not really asking...lol...

[Polkersince85]

I'd still change the Trans fluid and filter. Probably needs it anyway, so it couldn't hurt. My mother had a 93 Mercury that shifted hard like that, Changed fluid and filter and problem went away.

[RuSsMaN]

You can't diagnose this kind of thing online Trey. Find a car guy/gal in your area (any Polkies?) to drive it, and they'll get you pointed in the right direction.

A lock up Torque converter changes the final ratio to 1:1, there is no fourth gear - but it ACTS like there is one. I had a Buick for years with that kind of setup. GM has done it for a while, I can only assume Ford has dabbled with it also.

Cheers,
Russ

[VR3]

The more I drive it, the more normal it seems to be acting. None-the-less, when my Grandpaw returns, I shall throw the question his way, we are going to be putting some maintence on it soon, perfect time to ask questions (which I have alot of)...

Thanks for the toleration!

[HiPerf360]

Manufactures do not recommend towing with the converter unlocked, as you cannot control this. Transmissions in trucks often lock the converter in 2nd, 3rd, 4th and 5th gear if so equipped.

Older trucks recommended not towing in overdrive because of how the power was sent through the planetary gear set (when OD was new it was really an afterthought to an already existing trans.) and was very weak.

This is no longer the case and with transmissions being completely controlled by electronics it is no longer an issue to tow in OD as the computer will monitor trans temp, slippage, engine load vs. RPM etc.

When a TQ is in lock up it is effectively a clutch in a standard car, but when it is unlocked it has a multiplication factor of approx 2:1 in most cars at stall speed.

As you can see this gets very technical quite quickly so I could type all night.

OD and TQ lock up are two different things; there is a gear for OD.