How to find a 3:15 gear ratio differential for a first gen

Hello everyone, I just brought a first gen Taco two months ago and I’m very happy to have found it. It’s not fancy. Just a plain 2dr base model 2.4L 5 spd. So here is the thing, I t’s not that great on the high way so I wanted to switch out the differential for a lower gear ratio say a 3.15, mine came with a 3.58 gear ratio. How do I go about finding that differential or buying the ring and pinion gear? Does anyone know which year and option truck came with that? Thanks

 

3.15:1 is a higher gear ratio than 3.58:1, that would make it worse on the highway. You’re looking for a lower gear ratio (numerically higher), like 3.73:1 or 4.10:1.
A quick search indicates that others with 5 lug trucks have swapped complete third members from 6 lug (pre runner or 4x4) with no issues. The lower ratio gear sets will not fit on the carrier you have in your differential, you would be better off getting a full third member and swapping it in. Should be easy to find a 4.10 third member in a junk yard, just make sure it’s an open diff (no TRD e-locker).

 

3.15 came in the srunners. however it uses the 8.4" diff, rather than the 7.5 that comes in your truck. you'd have to swap the whole axle.
why do you want to go so low? 4cyl doesnt really have the torque .

 

Going up a tire size is an easier way to change your final drive ratio

 

What exactly do you want on the highway?

 

Hey guys thanks for responding. I’m not sure how to respond to each of you individually. So I have an 81 diesel Benz five speed and in the past I’ve changed the differential to a different gear ratio to help me get better speed on the highway. That car came with 55hp from the factory but yea it was a tremendous help. So I kinda wanted to do the same to the taco. On the highway I can go 70mph comfortably but anything above that it sounds like I’m pushing the engine to hard (I don’t have an rpm gauge). After posting the thread I learned that the 3.15 set up came in the second generation X-Runner 5spd. And yes that’s the 8.4” diff so I can’t really swap them out unfortunately. And yes I could get bigger tires but then the truck would look ugly lol. From what I understand is the lower the number the less torque but higher top end speed. With a 3.15 the drive shaft only has to spin 3.15 times to make the rear wheel spin once. If the number was higher the drive shaft would have to spin more times to have it rotate once which means your rpm’s would be higher to achieve the same speed.

 

How much torque does the diesel in that mercedes have? I bet its a lot more than the 4 cylinder gas engine in your taco at lower rpms.

Mine has 4.30 gears and so I went to a 32" in tire - ~11% taller than stock, putting me at roughly the equivalent of a 3.90. I wouldn't want to go any taller than that, I already have to downshift more than I like.

It would be interesting to look at your engine RPMs on the highway with an OBD reader, it'll be a lot more accurate than guessing by ear.

 

Every one had thought you wanted better throttle response not a higher cruising speed at lower engine rpm.

Being it is the 2WD is a add on overdrive an option I have not looked at these in at least 25 years.

 

The engine is just loud. Let er rip. You can do well over 120mph in 5th gear (if you unlocked the speed limiter)

FYI '01 and up 2WD 5-speeds have 3.58 gearing (except the S which has 3.15), '00 and previous have 3.42, maybe this is why you found different answers.

 

You know I have no idea how much torque it has but the engine has a compression ratio of 21:1. I put 500lbs in the taco the other day and it didn’t seem to bog it down at all. You can see the rpm’s through an OBD reader?? Cool!! I wonder if it has to be a fancy one though. Overdrive add on? I have no idea that’s a good question. 120?! No kidding? Lol. Yea it just gets loud and since I don’t have an rpm gauge I have no idea what’s going on under the hood. Maybe a 3.42 would help a bit. Does anyone know the rpm red line for that engine?

 

Lol