I know I shoulda checked this before I lifted the truck, but can someone tell me what their RPM is in OD at 70 MPH/auto trans/4.7. I put 35's on and I can't keep it in OD on the freeway. Looking to re-gear my rearend and want to know the RPM range.
Thanks,
Mike

 

I do not know to much about the 4.7 but with 35" on there would at least go to a 3.92 gearing to help recover of the lost TQ.

 

My 04 reg. cab 1500 4.7 auto 3.55 rear 245 70 17 tires= 1900 rpm @ 70 mph

 

Thanks rambob...That's exactly what I'm looking for! *cracks a cold one for rambob*

 

I double checked my RPM in OD last night and came up with 1900rpm @ 70 mph..hmmmm. My problem is I can't accelerate at all or it kicks down into third because of excess bogging. If I leave it in third on the freeway, it runs about 2500 rpm and will allow me to accelerate. I'm thinking I'll have to run 4:10's or 4:11's to fix my problem.

 

When I had my 02 1500 it had the 4.7L with the 3.92 limited slip rear end. It turned about 2200 RPM at 70 MPH with the 20" wheels and tires that came from the factory. It would drop out of OD any time there was an incline on the highway.

The little 4.7L is an ok engine and 230HP is plenty for a stock driver, but because of its small displacement, it only makes 295 lb-ft of torque, so in order to get the 230 HP, the trade-off is higher RPM's.

Seems the V-8's are getting smaller and smaller every year. For a car that's ok, reving it up and making it move is half the fun, but a truck needs high torque at lower RPM IMHO. It's a shame they did away with the 5.9L, that 360 was a great engine.

 

I am going to have to disagree with you, at least somewhat. Yes alot of torque is nice but not necessary. I previously owned a Toyota (Sorry) that I built up. 295lbft of torque would have been nice but I only had a 4 popper. I was lucky to get 100 lb ft of torque out of that. I had it on 9 total inches of lift and 35/14.5x15 tires. I could still do 80+ on the hwy although it did start to wander, and climb hills even better then it was stock. It is just a matter of gearing. rehawk996 if you install 4.10 gears your gear ratio will be slightly taller then it was stock allowing you to climb hills with ease and restore your power, 3.92 gears will not be quite enough although they would be considerably better that the current 3.55 ring and pinion's.

 

Since installing taller tired changes the "overall effective" ratio, I found these formula in a couple of truck mags. Hope this helps some.

Here is the formula for determing the true tire size
((((width*(aspect ratio/100)/25.4)*2)+rimsize))

Here is the formula for determining new gears to maintain the same performance.
(New Tire Height/Old Tire Height)*Current Gears=New gears