Hey y'all! I have just procured a 1993 Toyota pickup 4x4. It's got the 3.0 and the r150f. It's an awesome truck and I'm excited to be a part of the Yota gang. I've spent a lot of time on the forums looking for this exact question and have had little luck so I figured I'd make a post about it and maybe it could help some others in the future too.

So here's some details before I get into my question:
- The truck currently has 29" tires
- G254 rear end which should be 4.56:1 gears (if my research is correct)

Now, when I'm driving in 5th gear (.838:1) going 100kmph or ~60mph (confirmed with gps speedometer) the truck is at about 4000 rpm

This seems like super high rpm's compared to any other car or truck I've ever had and what other people get on the forums, I have made sure I am in 2H on the t-case as well lol! Most of the highways around me have a speed limit of 110 kmph and I don't even want to push it that far because I fee like its revving far too high.

Unfortunately I do not know the history of the truck nor does the previous owner. Is it possible the differential gears had been changed and that is why I am getting way higher RPM's? or is this actually normal and I'm just crazy. Maybe there's something else I am not considering.

Any input would be greatly appreciated. Thank y'all!

 

Just guessing: It has those gears because it probably has or came with add hubs/ tow package/ 31" tires.

Id throw some 31s on it and keep on truckin.

 

ya I think it was used for some towing so that could be it. Bigger tires are deffinately in the future of this rig but still just feels uncomfortable driving on the highway at 4000 rpm. Might just be something I live with or I’ll change the gearing down the road. Thanks!

 

Only two things can lower the revs at cruise>>
Taller tires or different gears in the diffs.

 

Ok, that's what I was thinking.

So I tried to use one of those online calculators (https://www.tremec.com/calculadora.php) to determine approximately what gears I would have in the rear end and if I put in all the information I got:

4000 rpm
.838:1 in 5th
60mph

the gear ratio in the rear I would actually have to be around 6.8:1 which I don't even think exists - maybe it does though.

I hope this is making sense to you but I am just so curious, maybe they changed the t-case gears too if that's even possible?

I know this doesn't matter a ton as I can still drive the truck around reliably but I am just curious and would like to know more about it if possible.

Thanks!

 

My '95 4Runner with R150F and 4.56 gears makes 70 MPH.(112.65KMH) @ about 3200 on 235 85 16's.
This tire is just short of 32 inches tall.
It is not possible to change the high range gears in the transfer case.
The transmission runs thru it 1 to 1 in high range.

 

well, a different transmission could, too - with a taller (numerically lower) OD.

 

I guess it could yes but it definitely is a r150f. I guess the only thing It could be is different gears in the diff right?

cheers

 

Give this a watch and maybe a try. ITs a way to take a guess at diff gears without taking the wheel off.

 

I just gave this a go, turns out I do in fact have 4.56 gears.

If I put all the information into a gear ratio to speed calculator, with a .838:1 5th gear, a 4.56:1 rear end and 29 inch tires, I should be going 90mph at 4000 rpm's, instead I'm only going about 62mph. That brings me to wonder if maybe my tachometer is reading higher at high rpms for some reason, I find that very unlikely as it seems to read accurate at idle but hey, electronics can be weird.

If anyone has any ideas as to what could be happening I'd really appreciate it. I know that this might not be that serious of an issue but I just feel so weird going 60mph at 4000 rpms. makes me feel bad for the poor 3.0

Is it possible my clutch is slipping at high rpms? it doesn't grab at all when I'm in first gear with the clutch all the way in but maybe it slips at higher revs.

Thanks!

 

a slipping clutch doesn't grab; it slips. if it grabs, it's good and not slipping.

 

A couple things to consider:

- Have you checked your braking system? You could have an issue (like a sticking caliper,) which would create drag, thereby resulting in higher RPM.

- What is your Idle RPM? It should be approx 800RPM. If it's high at idle, that will increase your RPM throughout the entire range.

- Check to ensure nobody has jumpered the test terminals looking for codes. If it was still jumpered, it could be throwing off the actual RPM (unlikely that much though.)

I hope this helps. I'm no expert, but learned a ton from this forum (mostly as a "lurker."). There are some great guys who are willing to help you out.