4cyl/man 4x4 gear swap questions.

Hello All, I purchased a '09 access cab 2.7 manual for may daughter a little back and its a great little truck that we have been doing minor upgrades to here and there. I would however like to posit the possibility of swapping in the differential and transfer case from a v6 into it to lower the final drive. If everything that I have seen is correct I currently have a 4.10 and this would drop it down to a 3.73, this would hopefully increase the fuel efficiency marginally without hurting 0-60 and cargo capacity/towing too bad. At the same time I would probably swap in a mechanical lsd. Im hoping that the speedometer should not be affected on this since it should be on the transfer case. It also thankfully looks like I should be able to pull the parts from a variety of trucks (Tacomas and 4runners, maybe more) Any input opinions on the validity of this? thanks in advance
-m

 

nobody would put 3.73. The engineers put 4.10 for a reason. Thats a standard ratio.

3.73 in V6 = complaints

4cyl is a small motor with less power. That’s why they gave it more leverage in the way of 4.10.
worse ratio can mean lugging which is not good and wastes fuel.

Idk what the front diff is. But the rear should be an 8.4
Many choices for a better diff in that. One option is TrueTrac.

the unknown part is a similar diff for the front. It has been done. Torsen style up front. Couple sites list it but idk if they actually have it in stock.

Not something I would do but that’s just me. I may be wrong.
Far as I know 4x4 4cyl manual was 4.10. Was probably a bit more designed for capability than its gardener spec counterpart.

I’ve heard the gardener spec ones
Ie 4cyl auto 2WD no flares, are same 8.4 but 3.58 ratio.

Audi b6 a4 commonly came with 3.889, 4.11, among other cars
and that’s lighter with less power/engine size, that doesn’t really wheel, tow, or haul.
Old P71 police interceptors, same thing. I think was 2.4L low power V8, 4.10.



^i want to copy this guys front setup I just don’t know what LSD he used or if it’s even obtainable now

 

from my research the 3.73 rear gear is standard for the v6 and I would say that the majority of owners have no issue with it. my guess is that the engineers put a 4.10 in because they did want to have any loss in towing capability or increase in 0-60. There are some on this forum that increase the differential to accommodate for larger tires and/or off-roading but neither of these are a concern for her truck. It could be an issue for towing in the future, but she never has anything heavier than her race bike on a single place trailer so maybe 650lbs total. 4.10s are often the optional gear for many trucks/suv including jeeps, s10's, rangers, frontiers, etc with the 3.73 being standard. I've run the gearing by my old race mechanic and he is guessing that it would give maybe 10% increase in mpg which, while not fantastic is significant and would increase the 0-60 from 8.5 to maybe 10.5 seconds. If I can find the right model 4runner or a 05-08 trd-sport tacoma I can do a plug and play front and rear with a lsd for a very reasonable price.

 

so you want to decrease 0-60 from 8.5s to 10.5s?
Do what you want, but consider the use of acceleration. Getting up to speed on a highway ramp to merge. Getting away from a bad situation like someone road raging. Etc
Power for towing that is lost even more when towing. Etc
Especially if towing through altitude on a trip on an N/A motor.

in theory yeah front and rear diff might drop in.
But if it’s a junkyard, many of them thing Tacoma means made of gold. Last price I checked on a front and rear 3.73 out of a crashed truck was asking $1200.

and that’s with the early clutch type mechanical rear LSD that is probably worn out by now and not a helical style.

 

This isn’t gonna be worth the effort, especially if you’re doing it to save money on gas. How many tanks is it gonna take to just break even on the parts and labor (I hope you value your own time?)?

Also, without the larger gearing the poor little motor is gonna have to work harder. Larger throttle angle will negate some of the mathematical mpg gains you are hoping for. And if she doesn’t off-road or really tow/haul (wrong truck for that anyway), then no LSD is needed either.

 

I might have an extra one I’d have to check (mech LSD) that I have no use for.

I’d imagine it might be swappable without messing with gears.

otherwise if gear setting is required, the cheapest route is dropping it off for a bench build, DIY, or use ECGS.

that’s depending on the condition of mech LSD and if rebuild parts are even available.
Otherwise TrueTrac is probably better.

a coworker installed lunchbox locker on his 3rd gen T4R without having to mess with gears. Not sure if the same applies to 2G taco.