Gear 4 Incorrect Ratio

thedude said:

"Gear 4 Incorrect Ratio" is the code my rr is throwing when i went to get it inspected. the code number is P0734. i have noticed that transmission almost pushes itself into overdrive gears such as 4th. so shifting is not as smooth as it should be.

what could the problem be and how would i fix it?

also, it threw codes P1172 and p1175 - Manufacturer Controlled Fuel and Air Metering. is this a failed MAF?

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all 3 faults are related to the mafs....check the fitting of the air box and make sure it is tight and not mis aligned if it is and the top of the air box is bent you may beable to bend back into shape but also may need a new box along with the new mafs

after you really should get the adaptions reset for the engine and trans at a dealer or indy shop with testbook or similar

You need a MAF.

JSQ said:

You need a MAF.

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X2 the gear 4 ratio has nothing to do w/ the transmission

When your MAF is going bad it it throws that 4th gear incorrect ratio code with the other two which are something like bank 1 or a too lean and bank b or 2 too lean... Anyways they will all go away when you replace the MAF and clear them...

WillTN said:

When your MAF is going bad it it throws that 4th gear incorrect ratio code with the other two which are something like bank 1 or a too lean and bank b or 2 too lean... Anyways they will all go away when you replace the MAF and clear them...

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correct.

just to throw a bit into this.

People always freak when they hear incorrect ratio and gear in that trouble code.

What the trouble code is actually saying is that while the truck is in 4th gear the 02 sensors are detecting a incorrect fuel air ratio. When the 02's detect the lean mixture it pops the code as being to lean. the reason it does it in 4th gear is because the base map is designed to lean the mixture in 4th gear for better highway mileage.

Very interesting thread. These are my exact symptoms. I did a little research on MAF and how they work. Pretty simple. I'm not sure what component actually fails. Thermistor, hot wire, op amp or the power transistor? The hot wire is basically a lightbulb element and that would be my guess. It could also be affected by contamination of a foreign metal causing the calibration curve to change. I examined those component carefully and notices they had a nice coat of dust on them. I wheel in an area where the soil is iron rich, so my theory is that it may have enough iron dust on it to change the resistance. I have used electrical contact cleaner on the elements and we'll see if it has any affect. I also found this neat explanation of how it works. I figured it is bad anyway,so will try this first if I have to buy one regardless. Will report the results if I have any update.

http://www.autoshop101.com/forms/h34.pdf

Do these codes ever clear themselves? I got the same code coming back from Big Bear Sunday. I cleared it and it came back a day later. I was going to drive it with the check engine light on for a day or so to see if it was going to throw the lean codes as well but it cleared itself today. A month ago it was throwing all 3 codes. I sprayed the MAF out with electical cleaner and they all went away for a month.

As a side question. Does the MAF affect the way the motor runs or is it just a smog thing?

Yes the MAF is fairly critical in helping the engine run- without it, the ECU has no idea how much air is entering the engine whether it's idle or wide open throttle. I've tried cleaning them with a variety of different products and have had repeat faults.
Muskyman gave an excellent description of the relationship of the transmission ECU and the engine ECU parameters.
I have an Autologic and have to go into the Transmission section to get the 4th gear fault even though the SES light was on. Dude, what scan tool were you using?

Isn't the Roverland unit used?