First automatic

For reasons I don't understand, Jeep evidently assembles the Quadra-Trac II

4H/4L/N transfer case with the Vari-Lok axle differentials and calls the whole thing Quadra-Drive II.

Cheers, Fred

That's so you have lots of big words to impress the logging equipment sales personnel. ;o)

Earle

I have driven the 05 Grand off road and know exacly what you are talking about. The transmisssion is a Mercedes triptronic unit and isn't usually used with such a low ratio. This means it shifts fast and harder than you might expect when in low As you no doubt have found by now the jump between 1st and 2 nd is quite big. The best thing I found was to run in 2nd and 3rd most of the time and when 1st was needed come to a complete stop before or as I down shifted into 1st.

Hope this helps John

John,

Thanks for the info and the analysis.

I think your advice about coming to a stop before shifting to 1 is the most sensible procedure too. I think I can make that a habit.

Thanks, Fred

I did not think that I had anything to contribute, but seeing Mr. Muddy's info i guess i do...

Wife and I own twin 1999 Jeep Grand Cherokees. What we have done on trips is rent the same car that we would think of buying and so last month, in Dallas, we rented a 2005 Jeep Grand Cherokee. We were very underwhelmed. Especially with the Tiptronic transmission. Leaving it alone, in D, it revved, then lugged, then when I put more push on the accelerator, it downshifted and revved like hell, then upshifted, and hit a small wall, then slowly deaccelerated, until It down shifted again. We had this turkey for a week and I figured out that the engine and the transmission are strangers to each other. So I figured out how to start it up, and it's in D, and I flip it left, left, left, to downshift, until i get what i want, then flip it right, then it gets up there then i flip it right, etc. I might as well be driving a manual shift. It just takes too much attention. It is very poorly designed.

And to top that off, all the nice amenities, like the rear of the steering wheel switches, the monitor in the ceiling - all gone. Maybe we rented the cheap model, but I sure didn't think so.

I got my Consumer Reports (they don't know anything about cars, remembering that in 1964 they thought that the Nash Rambler was the best car) but they voted the 2005 Jeep Grand Cherokee the worst SUV (whatever that is) that they tested.

So the Germans are now putting transmissions in US Jeeps? History has shown that the Germans have never understood Jeeps, and I spent 26 years in the US Army in Jeeps, and seven years in Germany talking to our German "sister" battalion people with Mercedes and VW wagons, and they said that they never understood how the US Army could do what they did with "The Jeep." and most off-road magazines don't show the Mercedes or VW doing all that well.

Bottom line. I have 115,000 miles on my 1999 Jeep Grand Cherokee, and will keep it for as long as I can, and then I'm looking at Hondas, whatever.

Talk about different strokes for different folks! I loved the transmission because you COULD shift it like a standard. However I have driven several different 05 Grands and the high range auto shift was seamless. It seems that the rental you pickup was suffering as rentals so often do. Also if it had no interior goodies then it was the bottom line "rental" special version.

John

Well folks.....

My 5 speed kinda acts the same when I am in 4 low and hit the granny gear or 1st. If I am moving and shift down into 1st which is very seldom, I warn the passenger to hang on so they don't go through the windshield.

I run 33" tires with 3.31 gears and my 1st gear is too low for any practical purposes besides a start pointing up a cliff or tree. When trail running, it basically never gets used.

I also figure I almost always only use it from a dead stop because when I do use it, my CJ feels like I am going to break something if I hit 1st low when moving or it will start bucking really bad. Body slams forward, down goes gas pedal, body slams back up comes gas pedal then body slams forward again....

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >

If you think about it your first gear ratio is about 3:1, your transfer case is about 3 (2.71:1 but we will stick to whole numbers to keep the math simple) and your rear end is 4:1.

Soooo 3 x 3 x 4 = 36:1 reduction.

Your engine is idling at 720 rpm (still keeping math simple) so your wheels are turning at 20 rpm.

A 33 inch tire turns about 600 revolutions per mile

1 mile/600 rev x 20 rev/min = 1/30 mile/min x 60 min/hr / 60 min/hr = 2 miles/hr

Therefore at whatever speed you are going when you drop it into first gear at an idle the engine, transmission, transfer case, and differential is going to do its best to slow you to 2 mph (x 1.6 = 3.6 kph) as rapidly as possible.

Why would you not expect a jolt?

As for Mike's driving habits...... just why does Mel allow you to drive?

Is this really a Tiptronic Transmission (Porsche design used found in Audis) or just another "sequential shifter"?

Because, when I'm driving a stick shift in 4L and I shift from 2 to 1, there's no jolt when I let out the clutch.

I just want the computer to be better than it is. Or than I am. Thazall.

Cheers, Fred

So you want it to slip on downloads into first when in 4Lo?

One thing to consider is that a nice, soft, smooth shift like what you want, is hell on clutches and other internal transmission parts. If you let out the clutch like I do on a stick shift, you might get a little jolt. This is because half-in, half-out is the position that causes the most wear. Also, the computer has no way of knowing what you are going to do in the next tenth of a second, like you do. It has no way of knowing what the next throttle opening position is going to be. For this reason, it is safer to have it shift gears in the quickest possible manner. Easier to write the code too.

Earle

Doing a manual downshift, I match transmission input speed to its ratioed output speed while the clutch is disengaged, and I don't slip the clutch.

Agreed.

It actually doesn't care. It just knows I clicked for a lower gear, and it queued up the request to work on when it gets a chance. It knows the engine speed, it knows the speeds of all the wheels, and it knows damn well what is going to happen when it slips its foot off the side of the clutch pedal.

Sure it does. It just set it a millisecond or two, and it'll set the next. If it's interested in what I think, it can read the position of the throttle pedal, but it can ignore that altogether if it chooses.

This, of course, is the crux. The easiest way to write code is to leave it out.

Thanks everyone for their contributions to this thread. Most of the time, I'm sorry I started it, but I've learned a lot, and I've collected a lot of good references.

This is one of the few functional newsgroups left.

Cheers, Fred

Thats a good question, I just heard it referred at a "tiptronic"

John