Ok ya'll.... I've been search the interwebs and all I can find is Miley Cyrus, lies and frustration. I have a 71 Hilux, 8RC and a 4spd. My truck tops out at ~70mph... and the engine is screaming blue bloody murder. Its happy at 55 in 4th gear... I have no idea what gears are in my truck, nor do I completely understand where I need to look. Furthermore I don't know what vehicle I need to pull the 3rd member out of, and stick in my truck. I really really really don't want to swap axles. I haven't been on here in a year so ya'll don't know me, but my axle kinda has to stay... I had a guy tell me at SEMA to use a Previa rear diff, but my buddy works for LKQ and said they have 4.30's in them. I've seen the diff threads, but they just give you a list... Hopefully the old school crew can help a brotha out! Anyhow,
from here How can I tell what gears are in my rearend? same idea for everybody Counting driveshaft rotations This is probably the easiest way to measure your rearend ratio, as it doesn't require removing the differential cover. Jack up the rear end of the truck (so that both rear tires are off the ground) and make a mark (or pick a spot) on both the driveshaft and a rear tire. With the transmission in neutral, spin the tire by hand through one rotation, and count the number of times the driveshaft turns. The number of driveshaft rotations is your rearend ratio. (For example, if the driveshaft turns about three and a half times, the ratio is probably 3.55. If its almost three and a quarter, the ratio is probably 3.21. Almost four times, 3.91s, etc. Note: The procedure above applies if you have a Sure Grip (limited slip) differential or a locker. If you have an open differential, the procedure is the same, but you will need to spin the tire through two rotations instead of just one. If you do not know what type of differential you have, see elsewhere in the DML FAQ to learn how to determine this. If you do not have a jack, you can also do this test on a level area by rolling the car enough to spin the tire once. Obviously, be extra careful if you do it this way (get a couple of buddies to help you) - jacking up the rear is safer.
Preicate the info and quick response. I don't have a diff cover to unbolt, so thats out. I DO have a jack LOL, but I don't know if I have a locker or posi or whatever. I was told that the 8RC doesn't match any of the 5spd bell housing patterns. But I haven't looked beyond that... so maybe. It seems easier to just swap the 3rd member. But i'm a sissy... LMAO... Any suggestion on high gear'd difs?
Toyota Differential Gear Guide this works if yoy still have a tag. i think these trucks are 4:30 something , there pretty low.
jack up the rear and spin one wheel, if the other spins the same you have limited slip or locker, if it spins the other way its an open. Yotas dont have diff covers, the whole 3rd unbolts and comes out the front side of the axle
you dont have limited slip if thats the orignal axle...easiest way to get more speed is to drop a diff with a lower gear ratio. you more the likley have the 3:56's, or 3:36's which means you can put the 3.07 ( lowest ratio toyota made ) in and get a lot more speeds outta your truck with out the trans swap. if you got the 3.07 in there already you are gonna have to drop in a 5 speed. you wont have to replace your axle, just the 3rd member which is the part the drive shaft attaches to in the FRONt of the axle ( if ya look you can see where it un bolts from the actual axle tube )
odds are you have a 4:37 G code 8in rear end. seems like most pre '75 trucks got em, 4:10's and higher started showing up after the gas crunch of the 70's. if you have a tag i bet it says G102 if no tag you'll need to pull the diff to properly identify it (size not ratio) but if its a G code, you have access to all kinds of better gears. like maybe a 3:07 out of a mkII supra. if your motor has the stones to push it you could see 120mph+ easy. but the real easy way for better gears is just another random G code 3rd member, should bolt right up to your current housing.
Thanks for all the feedback! I have a general understanding of 'no diff cover' and 3rd member etc... but I appreicate the clairification. So... where might I find this tag?
it might be under the hood on the ID plate on the driver side inner fender. i'm going to swap out the chunk on mine to,i'm going to go look. nope i bet it's held on with one of the 3rd members nuts
ive never actually seen your gen in person. on every other toyota ive seen its under the hood. stouts dont list tranny/axle code, so maybe yours might not list it either, dont know. i know it is listed under the hood from 73 on.
It is actually quite easy to work out your gear ratio. Jack the rear of the car up - make sure you do it safely, chock the front wheels, etc. Put the transmission in neutral. Put a small paint mark on the tailshaft/propshaft/driveshaft. Get a friend to fully rotate the rear wheel ten times. Count the number of times the tailshaft/propshaft/driveshaft turns. You'll then know your ratio. I'd imagine it will be about 4.8:1 if the Australian models are anything to go by. You will also have a build tag in your engine bay and it will (should) show a code like "G123" which you can look up - various websites have listings. However, the other option is more reliable as the tag can't tell you if the ratio has been changed or not in the past... the rotating wheels can't lie!! Also someone mentioned that you can use MkII supra gears in a G-series diff. Unless there is a difference in the US, this is incorrect. The MkII is the boxy early 80's model and that will have an F-series diff. The late 80s/early 90s MkIII has a G-series and you can use those gears no problems. In the Australian market every Hilux I have ever witnessed came with a G-series diff. You won't need to change your diff, just the centre.
