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Axle swap. Debating size/gearing


tsayyote

Active Member
Joined
Jan 14, 2013
Messages
27
City
Anaheim, CA
Vehicle Year
2002
Transmission
Manual
Hey guys, I think my rear axle is on its way out so I'm going to swap in another. Between 65-70mph I get a bad rumbling/vibration noise that sounds similar to driving on those lines that are cut into the side of the highway to let you know you're veering off the road.

I've got a '02 2.3L manual ext cab with axle code 87 (7.5 open 4.10). At highway speeds 70-75mph i'm at/above 3000rpm. I can't remember if these duratec 2.3's like to be at that rpm for mpg reasons, or not. I drive on Los Angeles freeways about 20 miles each way and its 50/50 chance of getting in very heavy traffic.

I'm wondering if I should stick with the 4.10 or entertain the thought of 3.73. I'd like to get a L/S rear too. I'm also thinking of swapping in the 8.8 from a ranger (I don't need discs right now, this is just my daily driver) or sticking with the 7.5 for weight reasons. Although, I don't know the weight difference between the 7.5/8.8 and if it would affect my mpg at all.

Any thoughts?
 
What kinda mileage you getting now? Being a '02 I'm guessing you have a one piece rear driveshaft, right? if not I'd suggest it as it could be the issue. With a 2.3L you probably wouldn't see much gain from going to the 8.8 axle as the main upside is it has a bigger crosspin which I didn't have a problem with even with a turbo engine and 4x4.

I imagine your tires aren't very tall, so it might not hurt to go to 3.73's, might have to downshift more but that's just a change in driving style.
 
Not really sure on the mileage yet. I bought the truck a couple months ago with a blown head gasket and recently just had a manufactured one dropped in and haven't gone through a full tank of gas yet.

The body has 213,xxx miles on it so it's possible it could be the shaft. It is also a one piece. My local driveline shop wants $140 for new u-joints and balance so I may take it over to him in the next few days. If its the shaft, the noise will intensify with speed, correct? This noise is only present between 65-70mph and disappears after that.
 
A bad ujoint will vary. It could be all good til a certain speed, then vibrate a little or like hell, and could even balance itself back out at a higher speed, or vibrate all the time. One sure way to tell is grab the driveshaft and try to move it in all 4 directions, and at both ends. The axle end is usually the end that goes bad first, but check both ends, if it moves at all, the joint needs replaced...

SVT
 
OK I'll check that out. My pinion seal is leaking, but the seal doesn't look real old as the orange paint on the seal isn't real dirty and that's what led me to believe the axle was on its way out.
 
Last edited:
Does this truck have a carrier bearing? When is the last time you serviced the transmission and rear diff?
 
Well I went to the junkyard today and talked to a guy about a rear assembly. He is going to build me one with 3.73 gears and a L/S for $450 with all new bearings and seals. Was a good deal so I went ahead with it. Picking it up on Friday. Dropping my driveshaft off tomorrow to get new u joints and balanced.

No carrier bearing. 1 piece steel shaft.

Had a mechanic look at the noise and he thought is was coming from the rear but couldn't pinpoint it. He said the transmission fluid looked good.
 

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