Well there's not anything wrong with the rear end but somthing isn't right somewhere. I did a rearend swap awhile back for some 4.11's from my stock 3.42's. I had the pcm tuned for them and everything, but something doesn't seem right. Before with the 3.42's I wouldn't shift out of 3rd until around 80mph now its around 70mph. That's not really the problem though, its 4th thats the problem. Now with the 4.11's I'm having to shift out of 4th into 5th at around 95mph at around 5600-6000RPMs. So that means I'm only seeing 20mph gain in 4th, from 70-95?? This can't be right can it? Because before with the 3.42's I wouldn't shift out of 4th til 110+ maybe can't remember exactly. But I know that I shouldn't be having to shift out of 4th at only 95mph...

Thanks in Advance for any help...

Kevin

 

Someone please correct me but I think that is normal. I have no experience with new gears though

 

*But to me it seems like I should be seeing more that a 20mph gain from 4th gear.* I have some 295/50r/15 BFG's on the back, which are right at about 26" tall. Could I possibly just need a taller tire. Because some people I know with 4.11's are trapping at 112 but with a 28" tire? But to me it doesn't seem like that would be the probelm...

*Edit

 

I was just hitting the rev limiter in 4th gear crossing the traps at 100-102.5. I had 245/50/16's. Yours sound about right....

 

Thanks for the input guys. Anyone else...?

 

What RPM are you shifting at? That will have a lot to do with your MPH at any given gear/rpm range. I have a cam/heads so I shift at 6500 and I'm going through the traps at around 6600 at 114-115mph in 4th with 4.10's.

Is your car stock? How tall are your rear tires? When my car was mostly stock with the 4.10's, I was trapping at 103-104mph. I just raised my rev limiter to around 6200 and held it in 4th through the traps.

Mike

 

I'm shifting at around 5800-6k. I have stock internals at the moment but have a CC306 waiting to be installed, just waiting on the other parts I need to do the install. The tires are right at about 26" tall. I think I answered all your questions. Do you think I just need a taller tire?

 

Nah just bump up your rev limiter. Especially with that cam to about 6200-6300. Should be okay then. If you want to get taller tires this will also solve your dilemma.

 

Definitely bump the rev limiter. The 306 will give you tons of power up top.

 

My rev limiter is already at 6500k, so that's already taken care of. I guess I need to hook autotap up and make a couple runs with it. Because I know the factory tach is off by a few hundered RPMs. Anyone else have any input? Thanks again guys...to me I was just thinking I would be seeing more than 20mph gain in 4th, but maybe not...