Rear end swap on 4.6???

[Nyexpy]

Hello fellow ford owners, this is my first expedition, ive had it for 2 years now and never gave me any problems until recently, when the rear end gave in. it just blew as I was driving. I figured its the rear since when I put in any gear it spins and all you hear is the grinding but the truck doesnt even move.. My question is being that my truck is a 97 4.6 base model can I use the rear of a 5.4 newer model expy? My local junkyard told me they only have 3.73 rears , but said I cant use em... Also what is a good loweing spring kit for my truck that doesnt go too low or mess with with suspension geometry? Thank you.....

 

[tonydiv]

I assume that the truck is 2 wheel drive. Because if it's 4 wheel drive, the front and rear axle ratios need to match.

In theory you should be able to put a rear axle assembly from any 97 to 02 Expedition in it. Why did they say that it wouldn't work?

 

[Nyexpy]

He just said its different because of the number of bolts on the diff cover and I cant use em. Im not sure about my truck being 2wd because it has 2h, 4awd, 4h, and 4l. I usually drive it in 2h which is rwd only so would that be 2wd model?

 

[panda24619]

well theres the problem. idk what the gear ratios are but if your going to buy a junk yard axle i would change the gears anyways. make them match and youll be fine. and the bolt pattern is also not the same. 10bolt/8.8 rear on the 4.6 to a 12bolt/9.75 rear on the 5.4. its a stronger axle. i would get it. everything should else should match up. like the suspension control arms shocks and coils. youll be fine. idk how to check what the gear ratios are but someone else will know. i would still get that axle.

 

[tonydiv]

The junkyard guy should know that it would work as a replacement axle for your truck. They have a crossover guide that should tell him which axles will fit.

If you're going to go to the trouble of swapping out the ring and pinion, you may as well just rebuild the stock 8.8" rear end. There are millions of limited slip diffs out there from mustangs and other cars / trucks, and the ring and pinion kit is pretty cheap.

The first thing I would do is jack the thing up and look inside the rear end. You need to find out what the failure was. It could be the ring or pinion gear or it could even be a broken axle shaft.

Whatever you end up doing, make damn sure that the gear ratio is the same as the front. Otherwise the moment you put it in 4wd, you will tear up the driveline.

 

[Nyexpy]

Im new to trucks so Im not too savy. so youre saying that I can use the 5.4 rear but only if I open it up snd swap gears? Im looking to just get a rear that is straight bolt on w/o getting additional parts. If not ill just end up getting the same diff

 

[nvycrmn]

chances are, you have the 8.8 front and rear. the 9.75 axle should match up just fine but not all of them have the 3.73 gears. i have that axle with 3.55 gears. there is a little tag on the differential that will tell you the axle size (8.8 or 9.75) and will also tell you gear ration (3.55 or 3.73). your best bet would be to look at the front and see what the little metal tag says for the front. that will give you a better idea of what to look for in the rear. but your rear diff should have a tag as well. either way, make sure you have the same gears in front and rear. i would go with the 9.75 if you can get one cheap. and i agree with tony, pull the diff cover off and take a few shots of what it looks like.

 

[99 Expy]

I'm sure the reason the guy told you it won't work is because the books show your truck with the 8.8" axle. A friend of mine recently had the same problem as you, and replaced it with a 9.75" the reason the other axle has more bolts is because it is the bigger axle. As long as the suspension mounts are in the same place, you will be fine. Just make sure you match your gear ratio like everyone else said. The reason different ratios will not work is because when both axles are given power, the wheels will turn at different speeds, and something will have to give.

 

[tonydiv]

The reason that you should open up the rear end is that it's possible that you broke an axle shaft. It that's the case, it's much cheaper and much easier to fix.

 

[Nyexpy]

Well I looked at the axle rear code on my vin tag in the door panel and it says h9. I looked it up and it means its a 3.55 lsd rear.. Im just gonna wait and see if I can locate the same rear at a junkyard, and maybe ill try to open it up this weekend and take a look inside..

 

[99 Expy]

You should be able to open up the rear end and check the axles and diff pretty easy. You just have to pop off the bolts on the back.