Hi all, I have a 78 hilux with a factory 5spd 2wd powered by a 20r. I’d like to be able to do 80mph down the freeway without the engine running @4k. What is a good gearing for my rear end to do so?
haha, one of the main reasons my 75 doesn't get driven regularly. Anything higher than the stock 4.10 gearing will lower the RPMs - so something in the 3.XX I believe all the 2wd trucks were 7.5" diff, so they won't work unless you swapped the whole axle assembly. I wanna say the only factory 3rd member with higher gearing that would work as a drop-in unit would be from a Tacoma/4runner 8.4 diff w/3.73 gearing. I've been on/off looking for one myself but people either don't know what they have or when they do it's priced near $300. I did find one a few months ago on CL for only $80 and now kicking myself because I passed on it, back pain + load/unload a complete axle assembly by myself just didn't seem like a great idea.
If the VIN plate and "decoder" are correct, my diff is a 8" diff with 4.10(i think) i have a W58 and mine runs at about 3k in 5th on ~24" tall tires
At what speed though? mine feels like 3500K+ rpms keeping up with traffic around 70-75mph range, 4.10 gears, 5th gear W50 and ~26” tall tires. Paired With that chambered muffler I’ve still got it’s nice and quiet at those speeds
I did a diff swap recently, from a late model Hilux to an early. The driveshaft flange was different which can be swapped. 3.58 RATIO, B04B is the code you're looking for. the speedo will also have to be recalibrated. have a look here to calculate the rpm drop for your vehicle, https://www.blocklayer.com/rpm-gear.aspx and here for the gearbox ratios https://www.toymods.org.au/forums/t...nual-Gearboxes-and-their-Ratios-(W-R-V-K-T-P)
Correction to what I said earlier - there ARE Toyota 8” diffs that have higher ratios than the 3.73 gearing - 3.14 and 3.58 are some others to look into. They’re more difficult to find as many 2wd trucks came with 7.5” differential. If you’re at a junkyard You can tell the difference between the two housings by the position of the top bolts. A 7.5” has bolt hole at 12-o’clock and the 8” have two holes at 11 and 1 o’clock
The 8” diff should have the code GO82 on your ID plate under the hood. This is actually a 3/4 ton axle. The gearing is 4.10. The GO82 axle shafts are interchangeable left or right. The 7.5 has unequal length shafts. Just a FYI, they no longer make the GO82 axle shafts. Not a problem for you, but a lot of motorhomes that used this axle with fake duel wheels had a major problem with the shafts breaking and the whole wheel and hub assembly falling off.
