With my 3.42's and a 30.5 inch tire, I'm right at 2000RPM at 70, Just wondering what your crusing RPM's are. I'd like to eventually get a set of 4.11's in.

 

Lucky i went from 3:23 to 3:73.. should of just gotten 4:11 o well

 

Feels great, staying under the 60 MPH so no idea of cruising RPM yet. I put so little miles on this truck, I bet it takes me months to get 500 miles

 

That's a huge jump. He went from 3.42s tho, not 3.23 like you.

That's still decent. I was told by a highly reputable place & someone there I trust, to go up 2 steps. That way, u feel it. So, 3.23 to 3.73 would be 2 steps. Likewise, for OP & me, a jump from 3.42 to 4.10s would again be 2 steps. Just my .02.

500 miles I can do inside of 5 wks.

 

My speedo is a little off since I haven't gotten my tune yet it's like 8-10mph off. At 60 mph it's right around 1800 70 is close to 2000 and 75 is like 2200 2300rpm not too sure yet. Il be dyne tuned next week on Tuesday since my tuner has some races thathje was getting ready for.

 

I had 24s with 275/30/24 but I'm back to 20s with 275/55/20. I love them I was out playing around last night and even with out my tune I can hear the tires screech shifting into 2nd.

 

who came up with the 500 mile thing anyways?

Are new vehicles broken in 500 miles prior to delivery?

I've read that the OEM gears are heat treated to 1500 F from the factory, unlike aftermarket gears.

I followed the 500 mile thing and changed the gear oil at that time....it looked new, so it seemed like a big waste of time. Maybe there was micro-particulates I couldn't see though...

 

GMCtrk, this is where I got that from, post 13. Unless, u meant generally speaking, most say to wait 500 mi to beat on it.

 

My installer is a 30 year Chevy tech. He does all the race cars in town setting up rearends. He said do the 20-30 minute, which he did mine on his lift in gear running. Then let cool. No towing for first couple hundred miles, moderate driving for a week or so then go. He has never changed oil. When I questioned, he said same thing. "New trucks dont get 'broke in', they go tow sometimes day after they are bought". He said I am welcome to change gear oil, but he has never seen an issue.

<shrugs shoulders>

yea, fastnblu, I dont drive very far each day, this wait 'could' be killer

 

There ya go, Michael, straight from the horse's mouth. It's like most things. Some adhere to it, some don't. Myself, I'll do it that way, I've seen breakin period mentioned plenty besides him. Why? Yes, swapping diff lube after said procedure, maybe it's a waste of time. But, a rear costs how much? Gears? Labor to install gears if not a DIY'er? Fluid & gasket are cheap in comparison. Ideally, I'd wanna do a breakin fluid change on a fresh rear, tranny, cam, or motor. Sometimes it doesn't happen. Fluids are cheap compared to those component replacement costs, labor & time. Your call.