Kolton5543

I recently traded my k10 for a clean 94 4runner. Its got a 3.0 and r150f on 30" tires still. From what I can tell its bone stock but the rpms confuse me. On the highway at 55, with the stock 4.10s, the calculators come out to be 2100 rpms. Thing is, this one runs at about 2700. Based on the calculators it should be about a 5.13 gear or so. I even installed an aftermarket tack to confirm the factory tach. Today I pulled the rear third to prep for a locker and found it actually has a 4.30 in it which I didn't even know was an available option. Still, that should only run it about 2220. Anybody have any ideas whats going here. It doesn't make any sense to me.

RJR

Two possibilities:
1) Your speedometer is way off. Have you checked it with a GPS? Your speedometer knows nothing about the rear-end ratio or tire size, so you might be running 65 mph when it says 55 mph.

2) You haven't shifted to 5th gear. Your numbers come out perfect for 4th gear with a 4:30 rear end.

4.56 was the standard gearing for a 3.0 5 speed with 31" tires. 4.10 should have been standard for the smaller 28" tires (P225x75x15, I think - it's what's on your door sticker). The 4.30 was in the auto's, as far as I know. Your vehicle might not be as bone stock as you think.

Kolton5543

I'll check the door tag and see what it has to say. I'm for sure in 5th gear. Speedo doesn't function at the time so GPS is my only option . I'll post numbers for all 5 gears in the morning. Just to be sure, 5th in an r150f is .838 correct? That's what I found on Marlins website and that's what I've been going by.if anything has been changed I'd assume it's been gearing. If the trans was originally an auto they did a very factory looking conversion. I think both front and rear have 4.30s. I haven't checked the front yet but after putting the my spare rear with 4.10s it feels like there is a slight bind in 4wheel now.

Kolton5543

So I just checked my speed at 1k 2k and 3k rpms in 1st-4th. Speed was checked using GPS on my phone. Current gears in the truck is 4.10. This is what I came out with

1st
6 11 15
2nd
10 20 28
3rd
16 28 41
4th
22 39 59
5th
25 45 74

Using a conversion calculator this is what it should be.

1st
5 11 17
2nd
10 21 31
3rd
15 30 45
4th
21 43 65
5th
25 51 77

Keep in mind all of my numbers are are rounded to the lowest whole number. Also the gps speedo isn't always dead on especially when constantly changing speeds so its numbers may be off +-1.
From what I can tell around 1k things seem to be pretty much dead on. 3k there's a little bit of discrepancy but not major. 2k there are major differences. As I said before I used a aftermarket tach connected to the ignition coil and it always gave the same reading as the factory tach. Honestly I don't know what to even think about the numbers and why there is such a large difference between 2k to 3k.

Kolton5543

Also I checked the door tag and it checks right. 4.30 is the original gearing
​​

RJR

Your calculated numbers look correct for 30" tires, which I think is what you say you have. I don't think 30" tires were common, but a 4.30 rear end would be correct for them.

I can't explain the 2000 rpm discrepancy either, other than something in the ignition system is causing the tachs (both of them) to mis-trigger at that speed and give you erroneous rpm data. If the ignition system was putting out occasional extra pulses, it would cause the tach(s) to read high and give you the results you are seeing. That's not an unreasonable theory - if you've ever put an oscilloscope on any of the electrical leads in your engine compartment, you'd be amazed at the amount of extraneous electrical noise there is. It's a horrible electrical environment.

Co_94_PU

iTrader: (-1)

Around five percent is the allowable error, don't sweat it..

No tire will be exactly thirty inches, and when the are they aren't for long. Hence we have an allowed error in the speedometer regulations..

atcfixer

iTrader: (1)

I was just about to post that lol, tire size is probably slightly smaller than 30in for actual size. Another possible thing could be a slipping clutch, but you'd probably notice it taking off a lot more than in cruise.

4.30 is kind of an odd ratio for a manual trans, does the door sticker say R150F too for the transmission? I've had a few 89-95 4x4's with the 3.0L and R150f trans, and all have been 4.10s. Maybe yours is a SR5, or maybe the original buyer wanted the tow package with out the larger tires (normally 4.56 gearing with 31in tires)?

Kolton5543

Yes it came with the r150f according to the door sticker. It is an sr5. I don't know if it's tow package though. It has a hitch but I'm not sure if it's stock or not. I'm fine with a little difference in the speedo especially since the rear tires are about half way worn. I'm just curious as to why around 2k it off so much for. Clutch definitely isn't slipping. It's brand new and grabs hard. I've yanked some pretty big trucks around with it already and shows no signs of wanting to give. You could be right about the extra ignition pulses but I would expect it to run rough of at all with that much extra. I suppose it could be just noise.

dropzone

iTrader: (6)

23 year old truck, no guarantee someone hasn't swapped gears. Heck I swapped gears 2x's in less than a year in one of my old trucks.

Co_94_PU

iTrader: (-1)

Aren't those actually 4.33?​​​​ or is my memory failing me

Kolton5543

43 ring gear teeth and 10 pinion teeth so no it's 4.3 even.