HZJ75 HP Diff question

[håvard]

Hi!
Does anyone know if the HZJ75 HP differential use the same Ring & Pinion and bearings as the HDJ80 HP diff?

In short, is the 75 HP diff the same as a 80 HP diff?

 

[PhrogsPhorever]

Yes, same 8" reverse cut ring and pinion.

 

[håvard]

Yes, same 8" reverse cut ring and pinion.

Thanks!
I know Toyota does some minor changes now and then. So i was a little confused when i checked parts numbers on 80 and 75 differential parts. They are not the same. But that doesnt mean they dont mix

EDIT: Are they also the same as LJ70/73 HP Rev diffs? In Short, Toyota only have one 8" HP diff?

 

[PhrogsPhorever]

I think it may be the same for the LJ, RJ, Bundera, etc, but I'm not positive.

 

[Radd Cruisers]

The R&P ratios from the 75 series and the 80 series are not necessarily the same - there are some different ratios used in each of those applications. 4.10s vs. 4.11s, and others like 4.3x etc.

The bearings and other small parts, from what I know, are the same - in the kits we list, the >1990 HP 8" use the same bearing kits. The electric locker 8" HP diffs use a different kit than the non-locker versions.

Give Roodogs in Australia a call or an email and they'll put you on the right track for parts. Or, you can JT's in Washington state (USA).


~John

 

[håvard]

The R&P ratios from the 75 series and the 80 series are not necessarily the same - there are some different ratios used in each of those applications. 4.10s vs. 4.11s, and others like 4.3x etc.

The bearings and other small parts, from what I know, are the same - in the kits we list, the >1990 HP 8" use the same bearing kits. The electric locker 8" HP diffs use a different kit than the non-locker versions.

Give Roodogs in Australia a call or an email and they'll put you on the right track for parts. Or, you can JT's in Washington state (USA).


~John

Thank you all. I thaught maybe 4.10 vs 4.11 was just a "matter of speach" and was in fact the same. But its not? Sounds strange since the 9,5" rear on these cars often got 4.11.

 

[Radd Cruisers]

Thank you all. I thaught maybe 4.10 vs 4.11 was just a "matter of speach" and was in fact the same. But its not? Sounds strange since the 9,5" rear on these cars often got 4.11.

I was under the impression, until I did some research recently, that when there was a move to the 1990 and later HP 8" diff that the ratio went from 4.11 to 4.10, but that is not the case.

For some reason, the HD 70 series in the 90s got 4.11s and the 80 series (for the most part) got 4.10s. The tooth counts on the gears are quite different with the 4.11s being a 37:9 and the 4.10s being a 41:10.

Why the vehicles with full time 4WD got one ratio and others got another ratio I haven't figured out yet. Perhaps it has to do with drivetrain harmonics or something - however, I really don't know.

The other oddity is that the earlier Land Cruisers (late 1970s through to 1990 [late 1989]) got 3.70s and then some of the 80 series got 3.73s with the taller gearing option in some markets.

The tooth counts for those are: 37:10 for the 3.70 and 41:11 for the 3.73. As you can see, the ring gear tooth counts stay the same even though it's a different profile I'm guessing, and the ring gear is somewhat thinner with the taller ratio. It would be interesting to see if the only difference in the ring gear profiles of is the thickness and that the teeth are pretty much the same... something I'll look in to when I get a chance. From a machining perspective, it would mean that you could cut one ring gear pattern for two ratios and only change the pinion gear... Maybe I'm out to lunch, but it is interesting to think about.


~John

 

[håvard]

Now im more confused than ever. I called justdifferentials.com. And i wanted to order a 4.11 RP set. My diff got 37/9 tooth count. (4.111111111111111).

Justdifferentials has a 4,10 kit. The guy at JustDifferentials was a 120% sure the 4.10 and 4.11 was the same.



Hmmmmmm. What to do, what to do!?

 

[Letsgomoreplaces]

Now im more confused than ever. I called justdifferentials.com. And i wanted to order a 4.11 RP set. My diff got 37/9 tooth count. (4.111111111111111).

Justdifferentials has a 4,10 kit. The guy at JustDifferentials was a 120% sure the 4.10 and 4.11 was the same.

Hmmmmmm. What to do, what to do!?

Install the 4.10 and be done. T8R-410R-NG. You will also need a flange. 37:9 and 41:10 are virtually identical. A few psi tire pressure would have more effect on rpm than the. 0.01 decimal. It is very common for oem applications to be different from front to rear by even greater margin. Don't sweat it. I have high doubts of the credibility of any source that would tell you otherwise.

 

[håvard]

Thanks JD.

The reason i have to triplecheck everything is that- if i order the wrong parts to Norway, there is no "practical" way to ship it back to the US. Believe me, i have tried.

I also talked to Nitro Gears. They also say that the 4.10 and 4.11 is the "same".

So, ill order a set of 4.10.