Rear Ends

[keithm]

I rebuilt the aod a couple of weeks ago, and go it installed this past weekend.
Install was very smooth and worked great afterward. Now that its running correctly I've noticed at 75 mph the engine is turning 3800. I have a 3:45 gear in it. 7.5 rear end, I know they made a 3:08, but did they make a 2:90

Keith

 

[brinker88]

0.18:1 difference between the 3.08 and the 2.90 won't even be a noticeable change...

 

[projectnitemare]

There is a 3.08 and a 2.73 offered for the 7.5. I wouldn't invest the money in a 7.5 that's in a V8 truck to be honest. Get an 8.8, install the gears in it and swap that axle in. The Explorer 8.8 will be the strongest due to the 31 spline axles but you will need to reweld the spring mounts. If you are into do that use a Ranger one and it's pretty much bolt in. You may have to source a driveshaft and or flanges depending on what is in yours already. Pretty sure the highest you can go on an 8.8 is 3.08 though. Ever consider playing around with tire size as well?

 

[RangerSVT]

If your turning 3800 rpm, you need to look at your tranny. You don't have overdrive kicking in. My V8 Trac with 410 gears is turning about 2600 at 75. 273 gears are available in an 8.8, but are found in mustangs, mostly foxbody...

SVT

 

[shane96ranger]

If your turning 3800 rpm, you need to look at your tranny. You don't have overdrive kicking in. My V8 Trac with 410 gears is turning about 2600 at 75. 273 gears are available in an 8.8, but are found in mustangs, mostly foxbody...

SVT

Agreed, that is really high. I don't think overdrive is working.

Was the kickdown cable installed correctly? You'll be building it again if it's not set right.

 

[bearsrngr]

x3 on this, I have 3.73s AOD and 26" tires turning 2000 @ 65. Also is you speedometer drive gear correct?

If your turning 3800 rpm, you need to look at your tranny. You don't have overdrive kicking in. My V8 Trac with 410 gears is turning about 2600 at 75. 273 gears are available in an 8.8, but are found in mustangs, mostly foxbody...

SVT

 

[keithm]

The transmission is definetly going into OD. The speedo gear is incorrect, it reads 10 mph faster then what your actually traveling. The first aod I had in it came from a town car, i was told it had a 2.90 or 2.92, although I can find nothing to verify that that gear even exists. There could also be a variance in the tach, I took the tach from a 86 f150 with a v8, I have not checked the calibration. It could be reading a little high. The only reason I'm concerned is the mpg is terrible, like a v8 is supposed to be good. Might be worth putting a 3.08 in it.

 

[keithm]

almost forgot it has 17" tires and other then the tag on the rear end indicating a 3.45 I have not verified that

 

[keithm]

the TV pressure is set to spec, shifts are smooth and consistent and you can feel all of them and see it on the tach also

 

[RangerSVT]

I get consistent 18 mpg highway at 60, drops to about 15-17 mpg at 75-80. You didn't state if you had efi or carb. If efi, check for codes, if carb, check your settings. Also, if carbed, what size you running?


SVT

 

[shane96ranger]

So you think your gearing is too low? What size are the tires? 17 inch doesn't tell us much. I would guess you are geared too high.

My F150 is geared too high, and I only get 14-15mpg's because the PO put bigger tires on it. I should probably be running a 4.10 gear.



EDIT: Forgot to mention that my F150 has 3.55's.

 

[85_Ranger4x4]

So you think your gearing is too low? What size are the tires? 17 inch doesn't tell us much. I would guess you are geared too high.

It would have be close to bare rims to have a chance of running that kind of RPM out of 3.45 gears with a functioning overdrive transmission.

The parents had a '94 Explorer with 3.27's and stock 235/75-15 tires, the only time it saw that kind of RPM was because the gutless 4.0 struggled on hills and it downshifted a lot.

Something is screwy somewhere, if the od is working and you have any kind of rubber on those rims you should not be anywhere near that RPM.

 

[keithm]

The tires are 255/45r17. The carb is a 600cfm carter. I went out today and did a highway gas mileage test, it would seem I'm getting about 18 mpg, not much to be concerned about. I'll hook up another tach tomorrow and see if I'm anywhere close.