I am going to either need a new differential, or get mine rebuilt soon. It is making a humming sound when going down the road (I jacked the rear end of the truck up and put it in drive to confirm that it is the diff, and not tires). I currently have a 8.8 inch 3.55 LS. I plan on getting bigger tires in the future, so I wanted to upgrade to 4.56 gears. Within the next year I do have plans on changing the 4.6l engine out with a 5.4 lightning with my cousin. I do not tow alot (a 20' pontoon about once or twice a year), but I do go off roading frequently, so the LS is something that I need. My question is, while I am getting a new (or rebuilt) rear end, should I try shopping around for a 9.75 inch rear and put in new gears, or get my current rear end rebuilt with improved gears....or any other suggestions?

Thanks

 

I think if you are going to put in a 5.4, definitely go with a 9.75. Also when you change the gears, don't forget the front diff.

 

A 9.75 with 4.56 and a detroit locker eace:

 

Sweet, thanks for the advice. I would prefer to have a LS, but I am fine with a locker. Is there any difference in the length of the drive shaft for the 8.8 and 9.75? I am also trying to not spend too much money, but if it is worth the extra cash, then I am all for it.

 

I believe you do have to modify your driveshaft, and you would have to do it again when you do the Lightning swap because the 4R100 is longer (?) than a 4R70.

 

If thats the case than you might as well stop now haha...lightning swap, gear swap, 9.75, and customs shafts, ain't nothing cheap, id do it the right way the first time, get a 9.75 from a parts truck with LS and build it up with gears and master overhaul kit, then i wouldn't install it until you put in the lightning...

 

I had my rear end rebuilt when it exploded and ended up paying $1200

If you already have big tires and a lift then the time you have for the rear end is running out. My suggestion if your on a budget; find a 9.75 rear end, buy the new gears for front and rear and have everything you need for the swap (do your hw). Wait until your rear end officially dies then have a mechanic, or you, switch your rear end with all your new parts.

I waited and waited on fixing my rear end and ended up paying a lot more then I wanted.

And like hunterjh said, do it when you have the lightning already installed. Good Luck

D

 

Ok guys, thanks for all of the replies and sorry for not replying in a while. The reason why I did not reply in a while was because I was going on a big road trip (I forgot to mention this), and I didn't want any troubles for the trip (seeing how it was about 1000 miles). I went ahead and bought a new rear end, had it built with the new gears (front and rear) and had it installed just in time for the trip. I would have waited till it went out, but I didn't want to take any chances. The new rear end (and gears) are in, and it works great. I wanted to try and save some money, because my tranny has been showing some signs of wear and I had no clue how long it would last, but it seems that this road trip kinda killed it, and I will be needing a new tranny sooner than I thought. The only rear end I could find in town was about 50 miles away for $450. To get the rear end installed and rebuilt with the new gears (front and rear) costed me about another $1500. The driveshaft DID have to be shortened by about 1 1/2 inches. The whole thing costed me a little less than $2,000, and I am selling the old rear so I will get some money back.
Now it is time to go tranny hunting .....will the torture ever end?

 

What gears did you end up getting?

 

I got 4.56 gears.

 

I put a new outer bearings in my 8.8. found a wheel bearing on rock auto closeout for $1.50 and outer Dana seals for 50 cents Ea.