I'm putting 4.56 gears in my 97 tommorow. i was just wondering what the break in period would be? Can i stomp on it right away and expect any gears left after awhile or do i need to drive "nicely" for awhile.

one more question. i would like to know what diff my truck has in it. i know its in the vin # but i dont know which numbers, letters it is. thanks JJ

 

After the first 15-20 miles let the diff cool completely before driving anymore. If you MUST tow, stop and let the diff cool every 15 miles or so. Avoid heavy acceleration for the first 500 miles. After 500 miles change the fluid and you should be good to go.

I've got a question for you, though. How are you installing gears in your truck if you don't even know what rearend you have?

 

New gears should go through numerous heat cycles before being considered "broken in". Though i do know people have gone right out and stomped them with no ill effects.........

 

I put about 150 miles on my new gears before I stomped on it. I just couldn't resist lol. I've got about 600 miles on them now with no problems as of yet.

 

sorry i didn't clarify. I have 3.55 and i went to 4.56. its an 8.8 what i was wondering is its a l/s or and open diff. sry about that

 

If you're doing the work yourself you'll be able to tell as soon as you pull off the cover. If you're having a shop do it, just ask them when they're finished. If it is limited slip they'll charge you for friction modifier. You can tell by the axle code on your door sticker, but if you're having the gears done today it's much easier just to look inside.

 

i pick the pickup up wendsday night. im pretty handy with a wrench but i didn't trust myself with putting in the gears as it would've been my first time installing gears. i was just curious as to what code means what on your vin#. i thought my owners manual said it was limmited slip. thanks for the input everyone said so far. really apreiciate it.

 

I don't believe there's anything in the actual VIN itself, but on the sticker in the door, there's a part that says "axle", and there's a two digit code under it. I personally don't know what they all mean, but Somebody else on here will. I do know that H9 is 3.55 LS. That's what I have (well before I regeared). Just post the code on here and somebody will tell you what it is. You can also search for it, there's gotta be at least a thousand threads asking the same question.

 

Contact the gear manufacturer and see what they recommend. The procedure varies from manufacturer to manufacturer. In general, 500-1000 miles without towing is all most of them recommend, but it varies.

-Joe

 

http://www.usgear.com/ring__pinion_installation.htm