HP 8" strength (1 Viewer)

[CYRUS]

After tossing around the idea of purchasing a LandCruiser for years, I've finally pulled the trigger on a '97 LX450.
Like any new owners, I have all these ideas that I want to do to my cruiser and one of them would be strengthening my axles especially the HP 8" front.
I'm planning to run 38" tire. Would doing axle truss, cromos 30/30 axle shafts and birfs, Nitro 5.29 gears and hellfire knuckles be strong enough for my tire of choice?
The reason why I ask is because I'm a little confused. People say to run these axles reliably, 35" would be max but I've seen lots of people running 37s and handful of people that actually wheels on these axles with 40" shoe and had no problems so what gives?

 

[White Stripe]

After tossing around the idea of purchasing a LandCruiser for years, I've finally pulled the trigger on a '97 LX450.
Like any new owners, I have all these ideas that I want to do to my cruiser and one of them would be strengthening my axles especially the HP 8" front.
I'm planning to run 38" tire. Would doing axle truss, cromos 30/30 axle shafts and birfs, Nitro 5.29 gears and hellfire knuckles be strong enough for my tire of choice?
The reason why I ask is because I'm a little confused. People say to run these axles reliably, 35" would be max but I've seen lots of people running 37s and handful of people that actually wheels on these axles with 40" shoe and had no problems so what gives?

Eventually if you build everything else up, the only weak spot becomes the 8" ring and pinion. The 38s will definitely strain it. The lower differential gears also makes it weaker. The bigger the pinion gear-the more teeth it has to meet up with the ring gear. If you are going to dump a bunch of money into a front toyota axle, I would start with either a custom front housing from diamond that can use a 9.5" differential, or take a fj60 front axle and use the 4+ axle housing inserts to make it as wide as the 80 rear and use custom length inner axles. You could then utilize the knuckle balls from the 80 housing or the 60 housing depending on what birfield you want to use. Using the 80 knuckle balls allows you to use your 80 steering components easier. In short, if your going to spend money on a front axle you don't want your differential to be the fuse or weak link, make the differential the strongest part.

 

[CYRUS]

Would running 37s on 4.88 gearing be any better or the 8" R&P is just not able to carry all that load pass a 35?

 

[White Stripe]

Would running 37s on 4.88 gearing be any better or the 8" R&P is just not able to carry all that load pass a 35?

37's and a heavy foot are known to be the point where it starts to be an issue.

 

[GW Nugget]

Doesn't the 4:88 have one more tooth on the pinion than a 5:29 set.

I think off the top of my head the one's that I know of that have 4Ds on a 80 are @Apounder & @Wrench , I know for sure he has 5:29s with a crawl box & wheels hardcore. I've seen some of his vids... I know he has broke some front end parts, but still runs the 8" front axle.

So, @Wrench will you please chime in here to give us you opinion also?
Thanks

 

[CYRUS]

I would love to hear from them for sure. Hopefully they chime in
Currently I do have 40" tires that came off my other truck that I've sold but I'm not sure if I want to use such big tire since I don't think I would be wheeling this that hard that's why I wanted to go to 38s

 

[CYRUS]

Just read thru Apounder's build thread and it makes me wanna do 40s now
Too bad my 40s are on 20" wheels. When i purchased my Toyo 40s they haven't had the 17" rim version and MTR kevlars was just too new so I went with the Toyos. They are heavy with such big rims so I pretty sure I'll snap that HP 8" like a twig but the wear like steel even under a heavy F350 superduty

 

[inkpot]

I would love to hear from them for sure. Hopefully they chime in
Currently I do have 40" tires that came off my other truck that I've sold but I'm not sure if I want to use such big tire since I don't think I would be wheeling this that hard that's why I wanted to go to 38s

It all depends on driver input, not what size tire you run. There are folks around here with over 100,000 miles on 37s and no problems in spite of lots of wheeling time.

 

[CYRUS]

I guess I'll just have to tie a string from my right toe to my nuts before I go wheeling

 

[ReformedJeeper]

I run 37's with RCV front axles. So far so good. What I am more worried about is twisting the rear axle splines (search for this because i have the factory elockers. I bought a landtank modified rear shaft. If you are running ARB lockers or open diff disregard my comment above.

 

[UWdave]

Eventually if you build everything else up, the only weak spot becomes the 8" ring and pinion. The 38s will definitely strain it. The lower differential gears also makes it weaker. The bigger the pinion gear-the more teeth it has to meet up with the ring gear. If you are going to dump a bunch of money into a front toyota axle, I would start with either a custom front housing from diamond that can use a 9.5" differential, or take a fj60 front axle and use the 4+ axle housing inserts to make it as wide as the 80 rear and use custom length inner axles. You could then utilize the knuckle balls from the 80 housing or the 60 housing depending on what birfield you want to use. Using the 80 knuckle balls allows you to use your 80 steering components easier. In short, if your going to spend money on a front axle you don't want your differential to be the fuse or weak link, make the differential the strongest part.

If I recall, a high pinion 8" is stronger than a LP 9.5" in the front.

 

[White Stripe]

If I recall, a high pinion 8" is stronger than a LP 9.5" in the front.

I have never heard of anybody breaking a front 9.5" differential ever.

 

[sailor]

Interesting. Lance ran Cooper 37s on 17" on stock front and 4.88 for years and never had an axle/diff issue... I was surprised. Until he rolled it, of course.

 

[Apounder]

Just read thru Apounder's build thread and it makes me wanna do 40s now
Too bad my 40s are on 20" wheels. When i purchased my Toyo 40s they haven't had the 17" rim version and MTR kevlars was just too new so I went with the Toyos. They are heavy with such big rims so I pretty sure I'll snap that HP 8" like a twig but the wear like steel even under a heavy F350 superduty

Idk if this helps, buuuut, I run 5.29s non cryo ( in my head it makes more sense to have a little softer metal with give then hardened ) anyway, I've run the 40in toyo soft compounds for over a year with no issues, take the truck wheeling at least 2 times a month, did some Browns camp airplane hill filters, lots of naches funny and moon rocks which are both fairly sticky rock, never had a single issue or felt hesitant on using some skinny pedal. But in my opinion people here are often over cautious, which isn't bad, just a lot different from the world of wheeling I'm use to. Hell most of the people I go with run 40s-42s on toyota axles with lots of skinny pedal and hopping in mini trucks.

Also being the 17in 40s with the steelies I had, my wheel/tire weight combo was 161lb per

 

[Whileemptyheadsdream]

I have never heard of anybody breaking a front 9.5" differential ever.

I believe what your saying. I built complete new thirds with toyota cases ,5.29 Nitro,.Koyo's and ARB Air , ft. and rear for my 95. In my research process I read several times that the 8'' H/P was the strongest diff Toyota ever made. Is the regearing what makes the 9.5 better or Is the Toyota claim just not accurate? I'm Just currious after what I have read. Good Luck !

 

[CYRUS]

I run 37's with RCV front axles. So far so good. What I am more worried about is twisting the rear axle splines (search for this because i have the factory elockers. I bought a landtank modified rear shaft. If you are running ARB lockers or open diff disregard my comment above.

How are landtank axles modified? Did they put a weak point mid way thru the shaft so it will break before the spline twists?

Idk if this helps, buuuut, I run 5.29s non cryo ( in my head it makes more sense to have a little softer metal with give then hardened ) anyway, I've run the 40in toyo soft compounds for over a year with no issues, take the truck wheeling at least 2 times a month, did some Browns camp airplane hill filters, lots of naches funny and moon rocks which are both fairly sticky rock, never had a single issue or felt hesitant on using some skinny pedal. But in my opinion people here are often over cautious, which isn't bad, just a lot different from the world of wheeling I'm use to. Hell most of the people I go with run 40s-42s on toyota axles with lots of skinny pedal and hopping in mini trucks.

Also being the 17in 40s with the steelies I had, my wheel/tire weight combo was 161lb per

Thanks for chiming in Apounder. That's is exactly my thoughts too that maybe most guys with LC80s are abit cautious and I agree it's not a bad thing. No every one want to get all greasy every time you go out on a wheeling trip, I know I don't.
When I had my Jeep rubicon I rode it hard too even with 38s on it. I'll be honest tho, I bent the ears abit just because the JK dana 44s are not true dana 44s to begin with but they held up pretty good. That being said, I was told the HP 8" are stronger than the Dana 44. So if my not quite true Dana 44 held up to decent abuse with 38s in trail why do people doubt the 8" can't handle the same abuse? I'm glad to hear that your axle is holding up pretty good because I'm really tempted to go with 4Ds again but on 17" wheel. Btw how do you like the MTRs compared to your toyo?

I believe what your saying. I built complete new thirds with toyota cases ,5.29 Nitro,.Koyo's and ARB Air , ft. and rear for my 95. In my research process I read several times that the 8'' H/P was the strongest diff Toyota ever made. Is the regearing what makes the 9.5 better or Is the Toyota claim just not accurate? I'm Just currious after what I have read. Good Luck !

I would like get to the bottom of this too before I go saving up for a diamond axle, not that it's a bad thing, but is it necessary for 37s and up wheelers. Is there a side by side pic comparison of a 8" and 9.5" ring gear both in 5.29

 

[slow95z]

Well I know here is different because we don't have rocks but mini trucks are often seen on 40+ tires with SBC swaps on 8" axles all the time. The 8" is much stronger than people think. If you are that worried about busting it and going to swap out stuff I see no reason to do anything less than a d60.

 

[Apounder]

How are landtank axles modified? Did they put a weak point mid way thru the shaft so it will break before the spline twists?



Thanks for chiming in Apounder. That's is exactly my thoughts too that maybe most guys with LC80s are abit cautious and I agree it's not a bad thing. No every one want to get all greasy every time you go out on a wheeling trip, I know I don't.
When I had my Jeep rubicon I rode it hard too even with 38s on it. I'll be honest tho, I bent the ears abit just because the JK dana 44s are not true dana 44s to begin with but they held up pretty good. That being said, I was told the HP 8" are stronger than the Dana 44. So if my not quite true Dana 44 held up to decent abuse with 38s in trail why do people doubt the 8" can't handle the same abuse? I'm glad to hear that your axle is holding up pretty good because I'm really tempted to go with 4Ds again but on 17" wheel. Btw how do you like the MTRs compared to your toyo?



I would like get to the bottom of this too before I go saving up for a diamond axle, not that it's a bad thing, but is it necessary for 37s and up wheelers. Is there a side by side pic comparison of a 8" and 9.5" ring gear both in 5.29

The MTRs kick ass, hands down one of my favorite tires.

 

[ReformedJeeper]

For the twisted spline issue read this thread:

Twisted Splines

It pretty much covers the whole issue.

 

[Whileemptyheadsdream]

How are landtank axles modified? Did they put a weak point mid way thru the shaft so it will break before the spline twists?



Thanks for chiming in Apounder. That's is exactly my thoughts too that maybe most guys with LC80s are abit cautious and I agree it's not a bad thing. No every one want to get all greasy every time you go out on a wheeling trip, I know I don't.
When I had my Jeep rubicon I rode it hard too even with 38s on it. I'll be honest tho, I bent the ears abit just because the JK dana 44s are not true dana 44s to begin with but they held up pretty good. That being said, I was told the HP 8" are stronger than the Dana 44. So if my not quite true Dana 44 held up to decent abuse with 38s in trail why do people doubt the 8" can't handle the same abuse? I'm glad to hear that your axle is holding up pretty good because I'm really tempted to go with 4Ds again but on 17" wheel. Btw how do you like the MTRs compared to your toyo?



I would like get to the bottom of this too before I go saving up for a diamond axle, not that it's a bad thing, but is it necessary for 37s and up wheelers. Is there a side by side pic comparison of a 8" and 9.5" ring gear both in 5.29

the 9.5 has my copper air line installed in pic. Hope this helps.