[purpledream]

I would like to talk to some of the fanatics that have done the 4:30 rear gear change and ask some questions !

What is engine rpm at 80 mph ?

What kind of difference is there in performance ?

How much does it help take off ?

Thanks
Tony

 

[tuckerred1948]

I would like to talk to some of the fanatics that have done the 4:30 rear gear change and ask some questions !

What is engine rpm at 80 mph ?

What kind of difference is there in performance ?

How much does it help take off ?

Thanks
Tony

That is interesting, from all of the threads I have read in the Forum in three or so years the only rear gears I have seen discussed other than the stock 3.73 were 4.10 and 4.56. I didn't know 4.30 was an option! 4.30 Gears in 04 Auto are PERFECT! Learn something new every day...

 

[dave rasmussen]

That is interesting, from all of the threads I have read in the Forum in three or so years the only rear gears I have seen discussed other than the stock 3.73 were 4.10 and 4.56. I didn't know 4.30 was an option! 4.30 Gears in 04 Auto are PERFECT! Learn something new every day...

I remember somewhere there was a chart. I can't help other than that as I have a 4:56 in a six speed. I guess that really didn't answer your question. Sorry.

 

[Mike in AZ]

I would like to talk to some of the fanatics that have done the 4:30 rear gear change and ask some questions !

What is engine rpm at 80 mph ?

What kind of difference is there in performance ?

How much does it help take off ?

Thanks
Tony

@purpledream

The answer to the gear ratio change is simple math.

Engine RPM at any given speed in any gear will be increased by the % change in gear ratio. In your case, 4.30/3.73 = 1.15. This means you will be turning 15% RPM more. Pick a speed, it doesn’t matter…… say you are currently turning 2,000 rpm at a given speed with 3.73 gears, you will be turning 2300 rpm at teh same speed with 4.30 gears.

With this knowledge, you should be able to predict that the increase in rear wheel torque will also be 15%. This is the same as adding 45 foot pounds of torque to the engine output.

Although you will have a 15% increase in torque, the takeoff is best helped with a good computer tune. This is fine in 49 of the 50 states. California won’t tolerate computer tunes much any more.

Regards,

Mike

 

[xs-cash]

4:56 in the 03/04 is highly recommended! Been there and done it !

 

[Daverobertson]

My 04 runs just a touch under 2800 rpm at 80mph. I put the 430s in about 2 years ago. Love the seat of the pants grunt. Add a Joe Delano tune right after that. Great runner and still get right at 18mpg on highway and in town. 2800rpm is right at the beginning of the power band on the 5.3. Put your leg in it running 80,let's just say it'll be north of 120mph before you can blink. The grin is great.

 

[purpledream]

I would like to talk to some of the fanatics that have done the 4:30 rear gear change and ask some questions !

What is engine rpm at 80 mph ?

What kind of difference is there in performance ?

How much does it help take off ?

Thanks
Tony

Thanks very much for the input fellow fanatics !!

 

[Dicktator]

I have had 4:10 gears for years now.

The difference is 400 rpm more at same speed as 3:73 gears.

Dicktator