Okay, I just bought a 1990 Ford F150 4WD with the 5.0L V8 EFI with the 4 Speed Automatic W/Overdrive. The Rear differential is going out at the Ring gear and Pinion. It is the 8.8 and 3.55 set up I believe. Would it be better to buy the entire set of replacement parts, i.e. new ring gear, pinion, internal gears, and try to do the job myself. Or try to find an entire rear axle and differential through a junk yard in useable condition and swap them out, installing my brakes and tires back onto the new axle? And what years/models could I use to replace it, I assume I don't have to find my exact replica model/year to use the differential of a donor vehicle?

Any details you guys could give me on the differential and what I should do would be greatly appreciated. I'm 17, it's my first truck, and it's worth saving, I just want to know how to do this on a low budget.

Thanks for you time and for any help you can offer. Devin

 

no, but you will need to possibly recalibrate your spedo and all that to any new gear set up you use if its not the same as your existing one that you have now, so really its up to you...

any 86-96 should bolt right in honestly

 

Well, what's your budget?

If you have the special tools required and the knowledge, then by all means set the gears up yourself. If you don't know what you're doing and don't have the tools, time, money, and inclination to do it right, then get a used axle.

A used axle out of an F-150 or Bronco will work but make sure the yoke style is the same. Older trucks used the yoke style pinion, and newer truck used a flange style pinion. Yours is right on the edge of when they changed it, so look carefully at what you have and go to the junkyard and compare.

When you buy a rear axle, inspect it carefully. Count the ring & pinion teeth, or look for the stamp on the ring gear. Make sure the side and spider gears aren't worn out. Make sure the pinion nut hasn't backed off, ruining the seal. If it leaks oil at the pinion, there's a good chance this happened.

 

You're gonning to have to do some shopping for axles to see what it'll cost to get one, in some areas they can be had for $100 but elsewhere they want $1000 for them. The good news is 3.55 gears were real common in these 1/2 tons so you shouldn't have too much problem finding potential donors in the scrapyard, then it's just a matter of determining if the ones you find are in good enough shape to consider buying. Parts to rebuild the axle you have will run about $300 give or take, but you also need special tools and some knowledge of how gearsets are installed.. it's not just a simple bolt-it in and forget it. As a result shops that do this charge anywhere from $500-1000 per axle.

 

Thanks for the replies guys. More than likely I'll look for a used rear end from a junk yard, so I'll be sure to inspect it for wear. I don't have the precision tools to set the gears right so It'd be best to get one used but in good shape, and install that on it in place of mine.

So am I correct in that a jolt when shifting gears and putting it in reverse is the rear differential going out? The previous owner said he had a mechanic look at it without opening the diff, and that that was the problem, could it possibly be the transmission though?

 

And my budget is about a grand at this time. Slowly over time I'll have more working 30 hours a week.

 

It depends on the local market for axles... Check your local junk yard and craigslist: los angeles classifieds for jobs, apartments, personals, for sale, services, community, and events to see what another 8.8 f150 rear end is going to cost you and then check that price against what new parts are going to cost... Also you have to take into account your ability to either just do a bolt up rear end or taking the time rebuild it. Do you have the time and tools to do it?

I know here in iowa I can pretty easily find a 8.8 w/ 3.55's for $100ish so I've never jumped into serious axle repair b/c bolting up another used axle is cheap and quick for me. Plus i get some $$$ back when the old axle goes to the scrap metal recyclers. keep in mind you probably want to take into account the condition of the overall axle including breaks, leaf pertches, and leafs if they come with. Remember to look at what you have to salvage off the old axle too.

Best of luck!

PS: it would be quick and easy to pop the rear diff cover and check for wear to make sure it's the diff before purchasing a used one. If i recall correctly it sould be 10 bolts on the back of the diff. if the diff is good you can just use some silicone to seal the diff back up and put some fresh 75w-140 back in (good maintence thing to do anyhow).

 

I would buy a used diff. Make sure tis the same gear reatio you already have, Can be had for $100 if you look. Once its in, Tear teh old one apart and see what is actually involved. Make it a learning process for next time. For that matter do some research adn try to reassemble it just for fun with the old parts and see how you fell about biulding a rear diff. They really arent that hard, but it does take time and luck/skill to get them to mesh correctly. Knowledge is power, Dont let a learning experience get away. Then itf you decide to regear later , rebuild that one and take your time to get it right.

 

Not necessarily. It could be as simple as bad u-joints. Put the t-case in neutral and reach under and twist the driveshaft to see where the play is. There should only be minimal play between the ring and pinion, which you will see between the pinion yoke and housing. If there's too much play, you should open the cover and see what's wrong.

And don't forget to post pics for us too!!!

 

^^when I read that, I thought the same thing, u joints.

 

Thats a great idea! There are alot of good reads on rebuilding 8.8's online too.

The OP is in AK, so who knows what a good used axle would go for up there. If its alot, just pop in a good shop, ask if they can rebuild axles and what they would charge with a new gearset.

Of course, first verify the axle you have is in need of repair.

I realized something was awry in my rear axle when I heard a loud snapping noise going up hill with a trailer on. Ended up being pinion bearings, luckily my ring & pinion were OK so I was able to reuse the gearset and same shims as stock just with all new bearings. Quiet as a mouse now! It was reeeaaalllyyy whining before this too.