I have a 98 tacoma 2.7L 4x4 with a custom camper on it so its hauling around a lot of permanent weight. The diff ratio is 3.58. Starting is a pain...it lugs and is difficult to start up hill. I have to max out the rpm range of each gear to get moving...4th on the freeway gets me to 70 with no umph left! I barely use 5th as I have to be on the flat or downhill and can only go 65 on flat.
Sooo... I'm looking to swap diffs and looking for advice on what I could expect in terms of performance from a 4.1 vs a 4.3???

 

What do you think your rig weighs? Pics? do you want to do much faster than 70? Stock size tires?

Id jump right to 4.56 or 4.88

 

You did not mention whether or not your tire size is stock. But a general rule of thumb is that if your tire size is say 10% over stock size, then you'd want to at least move up 10% in gear ratio to offset.

 

Tire size is 31x10.5. I'm not sure if that's stock or not. It's a fairly heavy load. Itd be nice to do 70-75 in 5th gear and have an easy start.

 

I am not sure how much your going to get even with a gear change it seems your 4 cylinder is working really hard just hauling your camper .

Gross weight would be really good to know.

Then you need to change front and rear gears .

I have seen charts that tell rpm changes with gear changes at a given tire size that gets you close. Pick the rpm that best works for your use.