Info needed

We have a 'new' to us Cutlass Ciera that does the exact same thing at that speed! It really just doesn't like it there. I think it was about

1700 rpm or so.

If I set the cruise a little higher or lower or lock out OD no issues.

It really freaked us the first time it did it up a long hill, suddenly two fast downshifts. After I bumped the cruise to just under 60 or about 1800 rpm, it only did the one shift on the hills.

Too many gears syndrome....

Mike

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

No, too tall a final drive ratio syndrome. The combo of tires and axle ratio is too tall so it downshifts alot on grades. You have three choices here, live with it, install smaller diameter tires or last install deeper axle ratios. No "chip' or tune or exhaust mod is going to fix this.

----------------- TheSnoMan.com

Actually, four. A blower helps. :) Why downshift when you can simply tap a few extra ponies.

Sometimes you can adjust the kickdown cable just a touch and that will solve the problem. Had to do that in my ZJ when towing a full trailer. Think I made it a couple of clicks looser, but still not slack.

The book recommends turning OD off when towing in steep hills.

The OP was at that speed 'just' before OD is recommended, 55 mph if you have a standard, so was my stock car with it's stock sized tires.

It is just the nature of the beast with that many gears and cruise control, there has to be a 'hunt' point where vacuum says a bog is happening.

I can get out of mine by a shot on the gas pedal too, the cruise just gets 'lost'.

If I 'have' to stay at 55, I lock out OD.

Mike

We have twin JGCs w/ 4.0L and automatics. We live in the Sierra Nevada and almost daily go from Placerville, CA at 1500 feet up to 4000 feet. We always take it out of Overdrive, going uphill (actually downhill also, but that's just preferance.) I personally only use Overdrive on the flat lands. I think that the "double hunt" is caused by low revs, resulting in too low speed, causing the downshift, but then even that is too low revs and speed for the throttle setting, so it downshifts again. Anyway, it doesn't hurt to keep the Overdrive locked out and see what happens.

Thanks everyone. Seems like we will have to live with the thing.

Just in case though, we live in Southern Illinois about 30 miles southeast of St. Louis. No real hills like some of you have mentioned. Barely bumps when you are talking about mountians. Also, we don't have factory stock tires. The dealer put on some bigger, more aggressive tires which probably affects the issue. And this is without towing also.

Hey Mike, you're in my neck of the woods

Darrell

It does not need to be none on my 4x4's hunt in and out of OD and one can hit it by 35 MPH too. The reason vacum drops is because gears are too tall. Detriot ships some vehicles with effective gearing so tall that while it might squeak them out a extra 1/2 MPG or so on EPA CAFE test for MPG rating it plays poorly in the real world. Slightly small diameter tires or a deeper axle ratio would cure it and likely improve overall MPG too because it would hunt less through gears. A super charger could fix it too but would hadd a lot of strain to tranny to overcome a tall effective drive ratio. There was a time when 4x4's were geared deeper by default but that time has long passed since they "civilized" many of them.

----------------- TheSnoMan.com

"DougW" wrote

Actually, four. A blower helps. :) Why downshift when you can simply tap a few extra ponies.

***PERK***

Blower?????!!!

Now you have MY attention!

Kate

Yep

I've been running a supercharger in the ZJ for going on nine years now.

downside is having to use higher octane fuel. $$ :/

I think we have a winner. If the dealership didn't change the final drive ratio when it added the larger tires then you would expect this kind of transmission behavior. You would need to change the final drive to at least

4.10:1 to get the engine back in its happy range at that speed. Or, under 55mph, just lock out overdrive.

Correct. I experienced the same with a '95 Impalla 3.4L.

Plus setup to stay in top gear too long. GM cars are famous for this.