Last time I had a question on this forum (not the Ford forum), I was dog cussed and ridiculed for not having a dedicated, heavy duty, rocker crawler/mudder. I am just an average Joe with average vehicle.

I have a 1991 F150 4x4. 5.0. 5 speed manual, lifted with 38.5" super Swampers, d-44 scissors up front and 8.8 on rear. has 4.56 gear front and back with detroit lockers. Well, the locker in the back broke after I discovered a loud pop in the rear . Did not stress it. I have given this truck to my son and he is fixing it. Yesterday, I bought 2 8.8 rear ends from a guy for 100.00 total and my son went & picked them up.

He and his friend pulled out the broken locker form our truck, and then he pulled the non locker component from one of the other stock rear ends. They went to install the replacement when they discovered that because of the 4.56 ring gear, the non locker will not fit, as a pin they say gets in the way. Only a locker will go in. My son does not want to fork out 500.00 or so because he says that it will only break again since this will be his driver around town for a while and lockers don't do well on pavement. I thought there were lockers that were auto and did not lock on pavement and sharp turns, but only engaged when needed. Please offer any advice for my situation. I know going to a 9", d-60 or 70 is the right thing to do and is what will eventually happen, but for now, he wants to get it going. Thanks again for any advice.

This truck is not a rock crawler or heavy duty mudder.

http://i127.photobucket.com/albums/p141/Rogmatt/laborday036.jpg

This is a "heavy duty rock crawler" website. If you don't like the responses you get, consider the source.

I think you're refering to the cross pin contacting the ring gear, not allowing it to slide into the carrier. You'll have this problem with a locker or not (depending on the locker). Take a dremel to the interfering ring gear tooth. Take out just enough material to allow the pin to slide into position.

Bray, I sincerely appreciate the response. I know i am out of my element, but this stuff is second nature to some of you, where I may never get an educated answer on lesser forums.

With a 4.56 or lower gear, you either need to grind the cross pin, or grind a tooth off the ring gear to make it fit.
Most people go for a tooth off the ring gear.

Grind the cross pin and source a second one as a spare.....

Thats the 1st Detroit I've ever heard of broken in an 8.8... usually everything else will break first. If he plans to keep the 38.5's, you will be better off leaving the carrier open. That is severely pushing it with an 8.8. If you get a stroger locker, you'll just break something else. While you're in there, do yourself a favor and weld the tubes to the center section (HogHead). Or you will be replacing U-joints in the DS before long

Don't grind the crosspin, grind the tooth. Throw some gear marking compound on it and make sure you're not grinding into the contact pattern, you'll be fine. If you'd rather not do that, buy a notched crosspin that has been hardened.

those "automatic" lockers you wanted to know about... a Detroit is one of those. good luck. there are "lunchbox" lockers that go in the open carrier that you have. but you still have to notch the ring gear, and you'll just break the carrier again. since the Detroit carrier is stronger than a stock one.

wow a detroit broke in the 8.8 ? did you check the shafts ? most detroit failures are due to the shafts breaking. and yes on most 4.56 and deeper gears you must grind a tooth down a little - your old gears were most likely ground, but when the ring gear was reinstalled it was clocked diffrently

and the open carrier is weaker than the detroit - svt broke 3 carriers with 37s -39s and a 300 strait 6. we welded the first two - the last was broke on the street - and it was open

id get a 9" from a early 80s f150 or bronco - it will bolt in and is stronger - but you will lose the tone ring - so no ABS

oh and a detroit is an auto lock by name, but anytime there is power applied it will lock - for a street rig id go open, or a selectable - like an arb

I did grind the tooth down, pin slipped in. Truck is cruising good now with the open dif. Thanks for all the help. Plan on getting a d-70 for the rear, and go solid D-60 on the front.