mx684

Ok cool. well i might put the stock ones back on and see how it does then....so if i put in say 4.10, with the 305's then it would be like with stock tires??

mx684

What would be the downfalls of using 4.10s???? if any..

J BODY

when towing heavy there really is no "downside" to the 4.10 gears. Back in the day anyone knowing they were going to be towing close to 10K or over that is what we recommended. Downside, in my opinion, was that when you did encounter a steep grade and chose, or had to, disengage OD you ended up creeping along at 45mph. My trailer is only around 8500 and being we used the truck for a "station wagon" more than a tool to tow I hated the 4.10's and swapped them out for the 3.55. Now empty I can enjoy decent mpg and keep the rpm's under 2k and stay with freeway traffic. OD off I can pull the trailer up steep grades at 55 and be at a decent rpm. Downside???? I'm looking at larger trailers and that will most likely put me in a position that I will regret getting rid of the 4.10's. It's extremely hard to have the best of both worlds. I retained the stock 265 tires. Even going with a nicer looking 285 would have most likely put me in an "un happy" rpm situation pulling the trailer. I'm really thinking a 3.7 or 3.9 gear would have been a nice option.

mx684

How much loss in fuel milage would i be sacraficing switchin to the 4.10s??

J BODY

I've always gotten 10-12 mpg pulling (4.10 and 3.55), but I don't tow slow.

Running empty I saw a 2-3mpg improvement going to the 3.55. Rpms dropped 400 at equal speeds.

.....of course the RV injectors I installed improved towing power to the point of having to build a trans. It does everything I want now with no fuss, no muss.

mx684

hmmm..maybe i need some injectors like that once i get my trans done...how many hp are they and about how much could i get a set for??

Huballa68

Get gauges on it .It will tell you alot.If you had a boost leak or weak turbo or pump or anything you'd see it in the gauges..

mx684

Well i will put them next on my list..given my tranny holds out..

ChrisM55

YOU really need to get those gauges before anything else. When the tech said you had good boost pressure he was reading it from the computer and if the MAP sensor is bad it might give it a false reading. Also, it could be a combination of things and you can't see it. Low fuel pressure coupled with low boost or such.

As far as the gears go. I have a 99 w/4.10 and get about 18-19 city and 22 empty hwy. towing my 32 foot trailer I can get about 12-14 but I drive about 60 MPH which is 2200 RPM's my sweet spot.

One thing I did notice, was you are running a chip with no gauges, thats a big NO NO and could have casued some of your problems


Good luck
Chris