3 questions 93 Ranger 4.0

[rkbonds1]

I do believe the knocking I'm hearing is just the valves echoing down and out the bottom because of the body lift and that's what's making it sound different/strange.

 

[rkbonds1]

Ok new problem the truck is idling at 2000 rpm's while going down the road and drops to between 1100 and 1300 rpm's when in park. If I unplug the IAC no change if I unplug the TPS the rpm's climb another 500 what's causing this? Any ideas?

 

[rkbonds1]

As for your gears, 4.88:1 is what would be ideal for 35" tires with the 4.0L engine.
I would jack one side up and do a check for what ratio is in there (if it's a std open diff or limited slip, spin the one tire TWO full revolutions while counting the driveshaft turns. 3¾ driveshaft turns = 3.73, 4.1 turns = 4.10, 4½ turns = 4.56, ~4¾ turns = 4.88 and so on. If less than 4.56, then that's going to be part of your mileage issue.

Finally got around to checking the gearing the way you suggested and what I came up with is 2 full tire rotations = 4 full drive shaft rotations. I don't think your chart went down that low so I'm guessing this would put me below optimal gearing. Any idea what ratio I am running now based off of this. Still puzzling to me is at 55 mph I'm under 2000 rpm's. I'm thinking once I do go to 33's instead of 35's I should be closer to the correct gear ratio?

 

[mr cribb]

Finally got around to checking the gearing the way you suggested and what I came up with is 2 full tire rotations = 4 full drive shaft rotations. I don't think your chart went down that low so I'm guessing this would put me below optimal gearing. Any idea what ratio I am running now based off of this. Still puzzling to me is at 55 mph I'm under 2000 rpm's. I'm thinking once I do go to 33's instead of 35's I should be closer to the correct gear ratio?

I traded a 94 ranger for my Explorer and it had 3.73 gears in the rear. However mine was the 2.3 4 cyl 5 speed.

Is there still a tag attached to the diff? By tag I mean small thin metal tag, it will have rear end size and gear ratio. The tag on my X axle reads 3 27 88 (or something like that) I can tell you from the first 3 numbers is I have an open diff w/ 3.27 gears. The second set of numbers is the axle size which in this case is the 8.8 rear end.

If it had a factory locker, and I think L/S rear it'd read 3L27

If by chance I severely over explained it.... please disregard.... I work amongst people that are dumber than my 1st grader.

 

[4x4junkie]

Finally got around to checking the gearing the way you suggested and what I came up with is 2 full tire rotations = 4 full drive shaft rotations. I don't think your chart went down that low so I'm guessing this would put me below optimal gearing. Any idea what ratio I am running now based off of this. Still puzzling to me is at 55 mph I'm under 2000 rpm's. I'm thinking once I do go to 33's instead of 35's I should be closer to the correct gear ratio?

Sounds like you have either 3.73 or 4.10s (checking a bit more precisely should tell you better which one it is, as there's nothing in between those offered for these axles).

Either way, you are well under what's ideal, correct. 33s would get you a little closer to ideal... 31s would put you right at ideal if it turns out you have 4.10s.

Ok new problem the truck is idling at 2000 rpm's while going down the road and drops to between 1100 and 1300 rpm's when in park. If I unplug the IAC no change if I unplug the TPS the rpm's climb another 500 what's causing this? Any ideas?

I would think a stuck IAC if nothing at all happened when you unplugged it.

 

[rkbonds1]

Took throttle body and IAC off and thoroughly cleaned them let it sit for a while then it idled correctly.... it still takes longer for the rpm's to drop than I would like but, I can live with it at least.