Is re-gearing my solution?

[Silverbullet]

On my current setup it seems that my gears are always on top of the turbos. When running down the highway there's not enough RPM to keep them working. Considering moving down to 4. 10's and wonder your opinions. I know this has been covered in depth, this was reflected in search results, but my situation may be a bit different.



Currently I'm running 3. 73 gears & 325/60-20's, (35. 4"). vs a standard 265/70-17, (31. 7") Using THIS calculator, I found in a search, this is what I cam up with.



Goal is optimum driving at 70mph. Figures based on . 7 OD in the 48re.



35's:

3. 73's @ 70mph = 1735rpm

4. 10's @ 70mph = 1907rpm

4. 30's @ 70mph = 2000rpm



31's:

3. 73's @ 70mph = 1937rpm

4. 10's @ 70mph = 2129rpm



Before spending the $$$$ to do a swap does this seem like a proper fix, vs. changing out chargers?



Driving impressions: The turbos spool incredibly well under hard acceleration. Though this vehicle is my DD and I like to just go with the flow of traffic. Stop light to light it smokes on me pretty good if I dont take off like a g-maw. On the highway it does ok until I start up a grade. It will lug a bit, smoke, and slowly the turbos will begin to light and smoke clears, partially because of how tight my t-converter is. I know that 4. 10's have a mpg dis-advantage, but running the larger tire it seems as I will be going back to where the typical rpm's are in a stock setup.



Any thoughts?

 

[rjrkihap]

I too use to play with gearing ratios vs. tire size. Based on your calculations, 4. 10's with 35's will put you right where you want to be. Just a thought, with a 4x4 your dealing with two axles. Perhaps you might want to look into a Gear Vendor (or other brand) under drive. It might actually pan-out to be less $$$ and hassle.

Have fun.

Ron

 

[Silverbullet]

I had'nt considered that. Mainly because I've got an auto making a over/under drive something to have to work while driving.



I definently understand on the 2 axles. It will be twice the price for a single solution. Although using the gearing swap will allow me to install a true-trac while the rear is out. Taking care of two birds with one stone.

 

[Paddy McMahon]

With Smarty on setting 3 or 5 my truck lugs less, smokes way less, and spools a little faster with the stock 265/70/17 tires on it compared to when I'm running my winter tires 295/70/17. This is especially noticeable between 45-60mph. I'd be inclined to believe that either more air from a faster spooling turbo or 4. 11 gears would help.

 

[Silverbullet]

Thanks. At this moment in time I'm thinking just rebuild the compounds. 62 over a 476 maby. Quicker spool my be my only answer.

 

[jelag]

I see that most of you are running accessories that turn up the HP... . but I'd like to put my 2 cents worth in about stock engines...

I have several work trucks all with the 4:10 pulling work trailers or running at GVW... . my kid owns the same truck with the 3. 73 as does my BIL... . both do 2-4 mpg better than I do all the time except with loads above 15,000 lbs... than we're even... . On the other hand they always do better MPG wise when the loads are less than 12,000... ... . None of these truck have their power turned up... .

My 08 5500 only came one way with the Auto... . and we're thinking of changing it to a lower ratio... . for fuel economy... . mind you... again a stock engine...

So with a stock truck I'd buy the lower ratio units... Geez, did I say that right... .

 

[JJPage]

Thanks. At this moment in time I'm thinking just rebuild the compounds. 62 over a 476 maby. Quicker spool my be my only answer.

I think your on to something here, I am not sure what a ED64 is, but with 90HP sticks, it can't spool easily at cruising speeds.



Just my thoughts after running a 62/74/14 as a single, it sucked at anything other than wot. So even if you go with a 62 as a secondary charger, I would pick a 65mm turbine, 71mm at the most.



Thats my opinion. Jess

 

[Silverbullet]

Took me a minuet to figure what ED 64 was myself. LOL. Engineered Diesel(ED). Yes what I'm working on is potential helpers to quicker spooling. I was thinking higher RPM's would help.