Clunky transmission question

[Stream 1529]

My '05 Ford transmission goes clunk when I first engage the tow-haul mode. This only happens when I am towing our trailer, and then it only occurs the first time I engage it. The TV hasn't towed in any mountains to date, so I don't use this mode very often. I've mainly used it to help coming to a stop.

I've talked with my allison friends and they say that doesn't happen to them. I had the tranny fluids changed about 6k miles ago, and the Ex has a total of 36k miles. So, is this normal or should I be running to the nearest dealer to get it checked out?

________Tom

[overlander63]

From what I am reading, the "clunk" you are hearing is driveline slop, and you hear it when the tow/haul is engaged while slowing down. This activates the "hold back" part of tow/haul, and is like throwing the transmission selector in a lower gear.
So, to answer your question, it is normal for the way you are using it, which is not the best way. If you are towing something, you should have the transmission in tow/haul, and leave it there. Don't go switching back and forth.

[Stream 1529]

Originally Posted by overlander63

So, to answer your question, it is normal for the way you are using it, which is not the best way. If you are towing something, you should have the transmission in tow/haul, and leave it there. Don't go switching back and forth.

Thanks, I had thought that its best use was to assist in hilly terrains, and for slowing. There aren't that many areas in my part of Texas where I would need this, so I haven't really formed a habit of always engaging this mode. When engaged, it takes much longer to move through the lower gears and so I haven't used it fearing it would be unnecessary strain on the transmission. This makes sense to a non-mechanical person, but appears to not be the correct conclusion from what you, and others, have said. We're going out again in a few weeks, and I'll try it this way and see how it performs.

__________Tom

[overlander63]

Originally Posted by Stream 1529

When engaged, it takes much longer to move through the lower gears

__________Tom

At the risk of sounding like a wiseguy, that's what it's there for.
It is easier on the transmission, it puts less strain on the clutches that way.If your truck has a transmission temp gauge, it should read lower when tow/haul is used while towing.

[Stream 1529]

Originally Posted by overlander63

It is easier on the transmission, it puts less strain on the clutches that way.If your truck has a transmission temp gauge, it should read lower when tow/haul is used while towing.

That's why I haven't been using it. My transmission temp gauge has always read right in the middle, never overheated. I'm going to try it out, if it'll be easier on the transmission I can learn to live with it.

[overlander63]

Ford for years has used "idiot gauges" that read dead center unless it is out of range. Oil pressure would be below 5psi, it would read dead center until it dropped below 5, then the gauge would drop to "0". I haven't dealt with the trans temp gauge, it may be a variation of the same critter.

[SilverToy]

Saw the comment about the 'idiot' gauges, and wondered if that was a wide spread thing ie. Gm have em too? I wonder since my Trans gauge (OEM, on a HD with trailer set-up and OEM trans cooler installed) DOES read up and down the 'range'.... but have always wondered if it is really accurate.

Is there a way to tell which type of gauge is installed? Is there a way to 'gauge' the effectiveness of the gauge short of adding another aftermarket setup?

Thanks for any and all input...!

Axel
SilverToy

[overlander63]

Originally Posted by SilverToy

Saw the comment about the 'idiot' gauges, and wondered if that was a wide spread thing ie. Gm have em too? I wonder since my Trans gauge (OEM, on a HD with trailer set-up and OEM trans cooler installed) DOES read up and down the 'range'.... but have always wondered if it is really accurate.

Is there a way to tell which type of gauge is installed? Is there a way to 'gauge' the effectiveness of the gauge short of adding another aftermarket setup?

Thanks for any and all input...!

Axel
SilverToy

The "idiot gauge" was developed because some Ford V8 engines suffered from chronic low oil pressure in the 80's, the gauge would read almost no oil pressure, but the engine would run 100,000 miles like that. After many complaints, the gauge was developed. It is basically a modified light, with what looks like a standard oil pressure switch on the engine, and what looks like a standard oil pressure gauge on the dash. The way it works is opposite the way the sender usually works, it grounds the gauge when it sees pressure, then the gauge swings into the "normal" area.
AFAIK, GM has not used this "fix". If you want to see what your oil pressure is, you can remove the sending unit, and install a mechanical gauge. After you verify what pressure your engine has, you will know what pressure your engine has at a given point in the gauge's swing. Electrical gauges are notoriously inaccurate anyway, the electrical oil pressure gauge on my truck shows very low, but the mechanical gauge shows 40psi.

[SilverToy]

Terry -

That is in essence, part of the problem I currently am having. Have looked all over the Haynes manual I have for the truck (01 k2500 Burb with Trailer package) - have not tracked down a factory manual.

I cannot find where the trans sender is located - I am fairly certain that I have the 4L80E on this truck, but there is NO INFO in the manual. Life is HUGELY hectic right now, otherwise I'd just lay down under there and spend time looking for it. Is there perhaps another sender location (in the sump perhaps?) where another sender, for a 2nd gauge, could easily be added?

Thanks for all thought....

Axel
SilverToy