Hey y'all I think this is a question's better asked here then the swap forums as I am not able to get answers at all and none about the axle's but feel free to tell me to beat it if this is the wrong spot.

I recently swapped my 92 4x4 3vz v6 r150 5 speed with 31.6" tires to a 1uz v8 engine and retained the r150 5 speed and transfer case, everything runs great but my conundrum lies in the gearing here and I was hoping for some thoughts, this truck is currently equipped and came with G284 = 4.300 axle setup. My problem is now even in 5th gear on the freeway at around 75 im sitting at almost 4000 rpms which is not really an issue for these motors but I am hoping to do some road tripping where speeds will be in the 70-80 mph range for hours on end.

The solution to me seems like a re gear is an absolute must but I am pretty lost on what my actual options are here outside of the lower 4.1 OEM re gear. my goal in the long run here is

33" tires at 70mph at around 2300-2500 RPM's

Do I try and go lower like a 3.9? Which I have only ever seen in 3rd gen runners and newer or will this not be compatible? or this a pretty unrealistically low gearing and speed goals? perhaps I should try something else to drop the RPMS?


Sorry in advance for yet another re gear thread but I couldn't find anything about gearing this low to accommodate such high rpms for this specific case especially about gearing down (I promise I searched )

 

Just bumping, hope someone might have some ideas :/

 

Regearing is about it but going from a 4.30 to a 4.10 isn’t a real big jump. Maybe a couple hundred rpm. Best bet is to go find a gear calculator online and start playing with ratios until you find what you want. I’d imagine you are looking at a 3.55 or so range to get the rpm’s down that low which is going to affect performance pretty significantly even with the v8.

 

Hey there, Thanks for the reply.

After some more measuring and accurately calculating I think I have a better idea of what im actually running as, as of yesterday with no wind or weight at 75 mph im sitting at closer to the 3,500 range, a little less then what I thought but still not comfortable enough personally for long distance where 80-85mph on freways is a factor, I would be sitting closer to the 3700-4000 range. These engines best preform for economy and general longevity at 2500-3000 for the types of distances I am hoping to drive.

According to my calculating my best best best possible setup would be running 3.90, that would give me the best total for the number I was looking for without drastically affecting performance, roughly 2502 RPMS at 75MPH
I agree with you about 3.58 gearing, it would be way to far over what I am aiming for and take away way too much power

my only issue now is where to find a 7.5" 3.90 third member that I can swap the carrier into my 7.5" front IFS

For whatever reason this gearset seems almost unobtainable, there is PLENTY of 8" 3.9s or 7.5" with every other ratio known to man. Is this just a axle configuration that never existed during this period? I have read and was told that the 22re 4cyl 2wd trucks tend to sometimes have a 7.5" dif but I have yet to see one with a 3.9" maybe they just never did?

For now im at a crossroads until I can source a 7.5 3.9 rear third member I can break down and put into my front IFS as again, 3.5 will be way too far the opposite direction. I know you can have a shop rebuild and regear the difs for the ratios I am looking for but anywhere near me with the current cost of parts and labor im looking at a price north of 2.5K for both

 

Something interesting of note is for whatever reason is the online calculators as far as I can see are not fully accurate or something is wrong with my truck/tacho which I calibrated accurately using a external laser tachometer that is accurate to +/ -0.5%

When plugging in my current setup it says I should be seeing about 2876 at 70 when in reality I am in the 3,400-3,500 range. I know external factors such as wind resistance, weight etc can play a roll but this sure seems like quite a drastic difference of at least 500 rpms of what I actually running at, bit thrown by that one. I am doubtful but curious if the PO re geared at some point and neglected to tell me, I'm going to the classic turn test and get an accurate check after work

 

Is it an automatic trans with torque converter slippage and/or lockup happening?

 

I have no idea if a 7.5” with a 3.90 gear set existed. More than likely not and you’ll need to have it regeared. Also, $2500 is probably on the low side unless that’s for one axle. My tundra for 5.29’s just ran me a bit over $4k. $2100 in gears and install kits and about $2k for install and fluids.

 

Nope, sadly not. Its a r150 5 speed and positive I am in 5th

 

Yea, also at the same conclusion it will 100% need a re gear.


Where it starts to get it real weird is the front IFS front dif, being a 7.5" vs the rear 8" things start to get a little funky. Obviously, this side is a lot more labor intensive. A 7.5" 3.9 also is pretty damn uncommon, it exists but man it seems like a unicorn. I did a ton of digging and found out these dif's really only exist in the the base level 2wd version of these trucks but even witth that they rarely got that ratio. The main factor there it honestly seems is just desirability, the 3,9's are pretty much worthless to just about everyone else with these trucks with a stock engine. Extremely luckily I was able to track one down for only $200 and guy had no idea why I would want it.


The rear is cake, the rear shaft unbolts and then 3rd member slides right out the back when unbolted.

Re gearing labor required in the front for these trucks is difficult but really not that bad, I reached out to zuk at http://www.gearinstalls.com/ that has specialized in toyota regears for a living to confirm my findings before I end up gearless and should be able to knock it out without issue and isnt anything I cannot handle. I also did locate 3.9 gear kits yukon sells for both the front and rear for $400 All in front 7.5 for $200 + $150 for the 8" rear and likely another 150-200 for lube and new bearings+shims for the 7.5" so roughly $550 and hopefully that ends up being it (I do have money ready incase it's not), I had both difs inspected for wear and also have all the tools needed for the IFS drop and gearing already.

 

Replying for the updates.


 

Sadly, still in a holding pattern.

I found a lead on 2 people with them, one of them dropped off the face of the planet but the other one does have one for sale and available to ship. Still working out the details but should get both in to do the re gear within the month depending on the temp outside (currently -10 in Wisconsin) , Im going to drop a few more WTB lines including on the classifieds here just to make sure im not overpaying

I would love to go to either 3.7 or 4.1 because of there availability but the difference in 4.1 just is not worth it and 3.7 will be too slow and too much of a power loss IMO unless anyone thinks otherwise

 

Going to make an interestingnote just incase anyone for some odd reason may need this in the future, a GREAT way to find these 3.9 difs is also checking MKI and MKII supras

https://www.yotatech.com/forums/f116...81/index2.html
79-81 (MKI) supras had a 7.5" solid axle, optional LSD
82-86 (MKII) supras have a 7.5" IRS, lsd

Meaning it will also be much easier for me to locate this ratio as they were very common on the MKI supras (actually a lot of info about them swapping truck difs in not as much the other way around)

 

Can you fit a taller tire instead of all this? Will a 33" tire get you where you want to be?

 

Man I wish, currently sitting on 31.6's and planning to move to 33's but it looks like it will barely make a difference from everything I have Heard/Read and the math, only about 150-200 RPMS

 

I haven't looked at any online gear calculators in a long time. Does the online gear calculator you used go by a 1:1 ratio for top gear transmission ratio or are you able to put in the ratio of your 5th gear over drive?

 

I am indeed, it accounts for the r150f 5'th gear of 0.84. This one specifically is great, has all of the Toyota boxes selectable from a drop down. Though again, a good bit off of my actual RPM numbers I get when driving for some reason

http://www.grimmjeeper.com/gears.html

 

The math doesn't lie. If the math doesn't match your tach, something is off. The only variable is "actual" tire size vs advertised size. As already mentioned, verify the actual gear ratio.
Are you positive that your tach that was originally for the 3.0 is reading accurately with the V8?

If the numbers you are putting into the calculator are correct, your tach should match. A little off because of more decimal points of the gear ratio (4.3xx) or tire variation is expected. A lot off tells me something is off with the numbers put in or the tach is not accurate.

I hope your find your solution and please post up whatever you decide to do.

 

The tach is accurate to the best of my knowledge, I utilized a external laser tachometer and using the crank hub verified RPMS are reflected accurately on the guage, I did this 2 or 3 times over a few week span just to make sure it is accurately reflecting. The engines responsiveness also accurately reflects on the tach (RPMS and rev limit are accurate to what the engines rev limit is, it also is accurate for idle RPMS and correctly shows what the 1uz idles at)

Unless something really weird is going on and the tach is loosing accuracy in the medium rpm range but accurate on the low end I don't think its the gauge, unless my logic is off. The numbers on the calculator is off by about 300-400 RPMS from what I am actually seeing on the gauge. Im still thrown what else could possibly creating that difference, I will likely pick up a external wired tach just to verify im not going crazy.

The only other scenario I can think of is the truck got slightly regeared at some point in it's life that I never was informed about which I am going to confirm later today by doing the tire rotation test.

I appreciate the thoughts and well wishes

 

I just tried some other online calculators. I looked up the OD ratio at .838 for the R150F and tried different tire sizes and gear ratios with 70 MPH as the speed. You would have to have 27" or 28" tires with a 4.88 gear set to get RPM at 3400 - 3500. Something isn't right. Maybe try another way to check your revs?

Sorry, I posted at the same time.

 

I thought going from a 22RE to the 3.4 I have now was a pretty good boost. That V8 must be a pretty stout power upgrade. I never did get my 4 cylinder tach to work though so I have no idea what my revs are. I have 5.29's and 37's.