Trying to be good with my 2004 6.8l RWD as I am towing, I replace the U-joints in the drive shaft as the truck is approaching 150k miles. I did mark all the parts so nothing gets rotated. Seems the driveshaft is out of balance, I did something wrong so I order another set of U-Joints and replace them again. It seemed better this time and towed the 7k lb car and trailer just over 500 miles. On the trip, I noticed a little whine, then on the way back, a louder whine. I'm guessing my drive shaft is still out of balance and has now ruined the pinion bearings, eating the ring and pinion. Pulled the plug and sampled the fluid, dark green/gray with a metal flake sheen to it. Metal in the diff fluid. I just checked with a local (Miami) suspension shop and he would want about $2k to rebuild it, and states the better option is to get a used rear axle from https://www.lkqonline.com/

I still have my stock 3.73 ratio and was thinking this might be a good time to step it up. I know, I know, many say to go to the big 4.56, but as I live and do most of my towing in flat, southern Florida, I'd go with the 4.30. I was towing 65mph @ 2000 rpm in 4th and getting 8.5 mph. I could sometimes get it up to 70 mph but when it downshifted, I'd have to back off to get it to upshift again else suffer with 7.3 mpg (or lower) in 3rd.

At any rate, https://www.lkqonline.com/ only offers the stock ratios. My question is, should I look for the 2004 diff for the Excursion, or is there another compatible diff I can look for? I'm also going to see about getting a replacement driveshaft as the cost of that is less than what they want to fix mine (even though they have not even seen mine yet). There seems to be 2 different shafts depending on the gear ration on the 6.8l?

 

Using the https://www.lkqonline.com/ site, I find that it is already matching up the different vehicles and years for me. Seems there is only one 4.30 diff in their system, and another option, the 4.10 diff, there are many of. But back to the driveshaft options, there are still only 2. One for the 3.73 and one for the 4.30. I did not see any listing for the 4.10.

 

I just bought a 1996 f150 I6 4.9 for 700 bucks. Got it home and got a closer look at it and the diff housing is falling apart. It's so rusted if I push hard enough my finger will go thru. Did some research and the housing is over 1000. Did some more research and found out a 9 inch is 200 bucks and a locking diff is 500 bucks (give or take) so I figure instead of buying the stocking housing for 1000 why not buy the good stuff for the same price. My only question is should I change my gear ratio while I'm down there. Currently it's a 3.08 with 35s. I want to make a sleeper out of it. So its gonna have money sunk into it.

 

Just found that Jegs has a reman supplier, ATK. But its almost $2000 for one of these. Includes axels. Jasper also does a reman, no price on them yet and it looks like they do not include the axels.

 

Your best bet is right here car-part.com remember that axle is super easy to get and superduty axles up to 2016 will also swap.

 

have you searched the florida junk yards ( aka auto recyclers). ?

there are a few rear sterling rear axles from Excursions with 4.30 gear sets in south florida that I see and many more from f250 trucks.
3.73 are plentiful….and cheap

start here
https://www.getusedparts.com/part/20...ursion#!search

 

as for your drive shaft being out of balance, yes that can ruin a pinion bearing.
is your excursion lifted or stock suspension ?
when you took apart the recently installed ujoints, did each bearing to see if you fell out during install ?
are you 100% certain the slip yoke splines were installed so the ujoints were properly phased ?
being out of balance, can you see where the factor balance weight was knocked off ?

what I am getting at is drive shafts seldom become unbalanced on their own, there is always some evidence of what is causing the vibration

 

Thanks, but that search shows 1 4.30 axle in south Fla, and 1 in North Fla. The one in the south (Homestead) has no condition and a $1 price tag. I'll have to call them to see if it really exists and condition. Yep, the 3.73's are more plentiful.

 

I installed an "Add-a-leaf" to the factory springs, lifted the rear end 2". When I put the trailer on with WD. it drops the rear about 3-4"

I checked each bearing, no needles missing. I also installed a completely new set just in case

Drew a line on the shaft at each end, on the trans tail shaft, on the rear, and on the yolk coupler. The truck was in park and never moved while the driveshaft was out so there was no way for anything to move and thus re-installing all the lines matched up.

I can see the factory weights and nothing looks amiss.

I am guessing when I pressed the old U-Joints out, I must have bent one ore more of the ears thus throwing the drive shaft off-center and out of balance. It will need to be trued/balanced or replaced as well.

 

I am looking at the attached. There is still about $390 in shipping to be added. A used complete 4.30 axle and a matching 4.30 driveshaft. No core charge or return of parts. This will let me bolt the used axle in and let me keep the old one to rebuild in the event that the junkyard one has issues. I was told upon delivery of the junkyard axle to pull the cover and inspect the gears and fluid before accepting.

This will get me more gear for towing as well. Am I missing anything?

 

have you searched Craigslist ?

dont know how far you want to drive but i see plenty of axles out of a f250 in florida, you would need to call to figure out ratios but they are out there.

this guy is a good start
https://tampa.craigslist.org/hil/pts...030759528.html

 

Other than my 1969 Shelby show car that the Excursion tows, this is also my DD transportation. The rear end whine is slowly getting louder, starting in at lower speeds. I'm not sure how long till it gets too bad to drive?

Yes, there are many rear axles out there, I have been looking. The problem is finding one with a 4.30 gear that fits. I can easily get a 3.73, but with everyone here on the forum saying you should go into the 4's when towing, would sticking with the 3.73 be the route to go?

 

All the sources I am looking at state the rear axle has to be from a EX, SD F250 from 02 to 05?

• 2002-2005 Ford Excursion - (10.50 RG), 4.30 ratio
• 2002-2004 Ford Pickup f250sd (Super Duty) - 4.30 ratio
• 2002 Ford Pickup f350sd (Super Duty) - 10.50 ring gear, SRW, 4.30 ratio (SRW), (tag V421 series)
• 2003-2004 Ford Pickup f350sd (Super Duty) - 10.50 ring gear, SRW, 4.30 ratio (SRW), tag V421 series

 

Can anyone confirm that the 3.73 and 3.40 rear's take different driveshafts? I don't even see a shaft listed for the 4.10, so maybe that was not an option for the 6.8L?

Update: Per the 03 sales brochure, the 4.10 ratio diff was only available for the 5.4 L Excursion

 

3.73 and 4.30 they take the same driveshaft. the only different drive shaft I am aware of is there are a few people who report having a double carden rear shaft but I have never actually seen one in person on a Ex or looked into which ex would have them. if your has a single joint on each end that is what the majority of Excursions have.

EDIT, this applies to the 4x4 models, I do not have first hand knowledge of the RWD shaft length. ( But I can look into if you like )
either way, I would take your shaft to a local driveline shop and have it balanced for your piece of mind however I am certain the vibration is a result of your increased ride height.