mrnick1979

I am currently collecting parts to do a TDI swap in a 96 Taco. I will be running a BRM engine, try to keep most of it stock, maybe a small tune, a R150 trans, and hopefully running stock gears. The truck now has 3.58 gears, i only plan on running 31-33 inch tires. I want to build it to get the best MPG hopefully (28-30mpg) as it will see a good bit of interstate miles. Using the rpm calculator it says 60mph around 2000 rpm, 75mph is around 2500rpm. 33 tires on the calculator says 60mph at 1850 rpm, and 75mph at 2300 rpm..... I am wondering about the turbo being happy and keeping temps down . I have read that these engines like the rpms around 1900-2200...

What gears and tire sizes are you guys running?
What mileage are you getting?

mrnick1979

I guess no one wants to chime in.....

PickleRick81

I'll chime in incase others are interested. I run the BHW 2.0 TDI found in the 2004 and 2005 Passat. I have one in my 87 R runner with a 2005 5 speed converted Passat b5.5


Like most of the 1.9 and 2.0 TDI motors the sweet spot is @1900 to 2400 rpms. They make small block Chevy torque in this range (300 ft lbs torque on my stock BHW with just a tune)


When cruising on the interstate with my lighter more aerodynamic Passat I make my best mpg right above that torque range.

I can cruise all day in my Passat at 3000 rpms and still net 40 plus mpg on the freeway.


Hitting 40 mpgs on the heavier, taller, brick aerodynamics of the 4runner is impossible. Just pulling a kayak trailer with 5 kayaks gets me mid 30s on a hwy beach trip in the Passat.


I'm also running the r150f but have 4.10 gears. 3000 rpms is what I consider the most rpms I'd want to maintain at a long cruising speed. I hit 88 mph @3000 rpms, this is good for me as I don't need to do 90. My target was 85mph on 285 70 17s @ 32 inches or so tall. I don't use 5 gear until right above 60 mph


4.30 gears would likely get me 84,. Since I want to hit 90 for short bursts(mine is a daily driver build). 4.10s suit me better.


The downfall to this is the 1st to 2nd gap is pretty big. 4.56 would be better for acceleration as I have to consciously over rev 1st to keep my shifts in peak torque range, something I'm not used to driving the 5 speed Passat daily. You may not have that issue as I jump from one to the other. The 4.56 gears would net me 80 or little less top cruising speed which isn't fast enough for 70mph posted speed limits.

Your gears should work for smaller 31 inch or smaller tires but you may find off road performance not as good, you'll have to ride te clutch to maneuver over obstacles at a safe slow pace and shift into low much more often. My 4.10s have the same issue. Since all the good off road local spots are now private property I won't need 4wd often.

If you look at VW Passat diesel gear ratios they are very similar (within 300 rpms) from their v6 counter parts ratios where you have an option for both motors. My Passat transmission for my diesel came from a v6 motor. The TDI revs much better than your Cummins 4bt motors that really hate even 2600 rpms

PickleRick81

After several weeks of driving I switched to 4.30 gears. At 45 mph on back country roads I was between 1800 and 2000 rpms. The TDI isn't happy lugging up hills at 45 mph, nearly 20 psi boost at 1900 rpms, she's much happier past 2k


I try to do 50 on these roads but traffic on the rush hour commute has issues even doing the posted speed limit most of the time.

The result is only about a 4.5% drop in rpms but in each gear it makes the engine happier at common 35 and 45 mph speeds in 3rd and 4th gear. I don't have an egt gauge yet but it is on order.