I'm iPhone illiterate so I'll do my best to keep this readable/understAndable. Today after a round Of disc golf, as I was turning out of the park, I could feel something weird in the rear end then a loud CLUNK/POP and the whole truck shook. It did this a few times and I pulled into a church parking lot. Straight forward and straight back it doesn't do it but while turning either direction and in forward or reverse motion it sounds like its gonna explode. I nArrowed it down to the drivers side I think. My question is what could it be? I searched and didn't find much other than pinion issues and loss fluid related issues, but my u joints are recent and there is no fluid loss from my differential or axle seAls. Any ideas?

 

Also, this a 4.9l with 5 speed and manual shift 4x4 not electric. 35s and skyjacker 4 inch lift.

 

Not sure if there are clutch plates in that rear end like newer ones....but that is just how a van I drove sounded. It needed the rear end fluid changed and friction modifier added. Once that was done, all was good.

 

I am definitely going to check the tag and open her up when my buddy gets off work, he has a nice work truck with a compressor and tools.

 

open the rear diff cover and inspect. the Limited slip will do this and destroy the spider gears. if all looks well reseal and like mentioned add gear oil and friction modifier otherwise you will have major problems.

start looking for either an LS rebuild kit from ford or get an upgraded locker/limited slip.

what gears do you have in that rig?

 

Alright. Brace yourself for bad news. Spider gears are missing teeth. I found their shattered carcasses in the trench just behind the diff cover. Everything else appears to be ok and no weird scarring or scratching. Question is, do I rebuild or replace? I'd love the opportunity to tear it apart and fix it but is it cost effective? I have no idea what my ratios are, PO was also unsure. Speedo appears to be correct on the highway. And the rear end appeared to be stock(nice milkshake of gear oil that smelled old and burnt, probably stock too!) pictures soon

 

And I just realized I am awful at searching on these forums. Sorry guys.

 

Well I did a rebuild on mine and total was about 280$. If its stock gears (3.55) then I thought I read someone said you could buy the whole rear end from a junk yard for about 100-200$. If you do it yourself and have the tools you will save tons of money.

check this out...
https://www.ford-trucks.com/forums/1...ajor-pain.html

 

you need to figure out the gear ratio. you can either count the teeth. or jack the rear end up and rotate the tire a full 360* and count how many times the rear driveshaft makes a complete rotation.

most 300-6/5speed trucks had 3.08 gears. the speedo in that year truck can be calibrated to the size tire you have but that doesnt mean anything regarding the gears. is it peppy around town or is it a dog. when driving 65mph what rpms are you at?

with 35" tires you should run at least 4.56 gears, i run 4.88's and love the setup but i also have an auto tranny.

ford may still sell the Limited slip rebuild kit for around $80 if i recall. that would be the cheapest option.

 

Peppy around town for sure and not too bad on the highway. Guess I'm tearing her down today.

 

So my driveshaft spins 3 times for every 1 turn of the wheels. Door code is 18. But I don't think its 3.08 at least I hope not.

 

Picked up 2 flawless looking spider gears from the same rear end on an F150 at the junkyard for pretty cheap. They go in tomorrow!

 

I just learned from a friend that the C clips and pins in the 8.8 can go bad really quick. Maybe take a look while the gears are out?

 

So, after another trip to the junk yard, I got the correct gears. The first set I removed from an early 80's 4x4 F150 with the same drivetrain and the spiders were smaller. After a pricing fiasco I removed another set from an 89 F150 with the H8 rear end. The gears were identical. I installed them in my Bronco and sealed up the diff and filled it with gear oil. First rear end I've put my hands on honestly. Just drove from Greenville, SC to Boone, NC packed full for my move and no problems. No noise, no clunking, nothing. Only used a quarter tank to get here too.
Now for the new problem: No brake pressure at the pedal. Pumping does not increase the pressure either. No visible leaks I've found as of yet. Newbie to brakes too aside from brake pad changes and rotor replacement. Geeeez.

 

i hope you put friction modifer into the gear oil otherwise you will destroy your spiders again.

have you checked your brake fluid?