Are 5.29s really weaker than 4.88s?

[4WD Toyota Owner Magazine]

Did a search and found several threads that touch on this briefly. Some say 5.29s are weaker (smaller pinion?) yet Christo Slee has Yukon 5.29s in the shortbus and never has had a problem but blew up two sets of 4.88s. One guy posted that his Precision 4.88s went kaboom.

Is it in fact the simple fact that anything can and will break while offroading, or does anyone have definitive stats or facts that one is weaker than the other (4.88 vs 5.20, not Precision vs Yukon etc), or that both are fine and it's the driver repeatedly slamming his truck up a rock ledge, wildly spinning his tires, until his diffs implode?

So....looking to hear from you...anyone blown up their ring and pinion, if so, what gearing and HOW did it happen?

 

[FJ40Jim]

You ask 2 questions:
Yes, 5.29's are weaker than 4.88's.

Simple facts. Fewer teeth on pinion=more stress on each tooth.
Smaller diameter pinion=more load at gear face.

FWIW, numerically higher ratios are almost always weaker.

Who's broken them?
I dunno, I haven't seen too many broken 5.29's in Minis/80's.

 

[Cube Dweller]

David, I've been researching this too and all I could find between mud and pirate is anecdotal ramblings. Someone here posted a link to Zuk's page(I don't know Zuk, but he seems to build quite a few Toy 3rd's) and his theory is the preload on the carrier bearing is typically set too low and this allows the ring gear to deflect under load, causing damage. It would be interesting to see this modeled as I would think that once you hit a certain preload the slop is taken out of the carrier bearing and any deflection is a result of the material property (modulus of elasticity) and geometry.

For my runner elocker hi-pinion I sent the R&P to Bobby Long. I didn't actually ask him what he does in addition to the cryo treating. My guess is that if he redoes the heat treating, he's dropping the hardness to increase the toughness (better for shock loading). This would reduce the life of the gears, which I'm not concerned about since it's going into a part time 4wd rig, so the front dif will see relatively little use. In an 80, it might matter.

FWIW, I chose 4.88's with 35's. My runner will have dual cases and a 3.0 v-6. My rationale was I dislike wrenching in the dirt and blowing a front third on the Rubicon would really suck, and I don't have an extra $1000 to pony up for a spare front 3rd.

Edit: One of the other considerations for me was that my rear dif was already 4.88's from when I ran 33's. I'm getting ready to do an SAS, so it was buy one R&P at 4.88 or two at 5.29. Plus install.

One man's opinion.

 

[Walking Eagle]

Someone posted a link some time ago to a site that delved in detail why 5.29 were actually stronger. Most of the comparisions they were making, sure made sense, though I never sat down to deeply analize it, and it certainly went against most of what you read in the rags that larger is weeker.

 

[DirtyHarry]

Here is Zuk's page:

http://www.gearinstalls.com/410suck.htm

Between the cushioning of the automatic transmission, the fact that most of us are still running 4.10s in our 80s, and the scarcity of 80s that are actually wheeled HARD, I don't think that you are going to find enough feedback in this forum to reach any sort of real conclusion.

 

[Nay]

I think this is the wrong comparison...you are working off of empirical data from two R&P sets laying on a bench, which is, IMHO, irrelvant.

There are two issues:

1) Is a 5.29 R&P properly installed now the weak point over birfs or axle shafts?
2) How is said R&P being used?


The point of lower gears offroad is to allow a higher crawl ratio, which means less need for the engine to supply the necessary torque. Let's take a more polarized example:

We are both running 35's, but I have decided to stay at stock 4.10's for a variety of reasons. You have gone to 5.29's because highway gearing means nothing to you since your rig is a trail rig. I have a much stronger setup, right?

Maybe not. In practice, with all else being equal including the driver, you should have a much easier time crawling up obstacles than I will. I am probably going to have to "bump" with throttle more than you will, and that's when stuff breaks. In other words, I am much more likely to shock load my setup than you are. My R&P may hold, but because I am undergeared, I may blow the fuse in my system, which is probably a birf, maybe an axle shaft. You on the other hand may crawl through everything, have a nice meal and a beer, and drive home.

My point is this: undergearing somewhat on 4.88's (say for 37" tires) in order to have a "stronger" R&P is probably a mistake, unless you are gaining crawl ratio through a t-case swap or some other means (although that means more torque run through the R&P anyway). If you are running trails where there is a serious risk of blowing the R&P, then it is not realistic to believe that undergearing is an advantage in any way.

Nay

 

[locrwln1]

I had an 88 3.0 4runner with dual cases. I did the SAS and added a '83 and then and '85 housing (story for another time). I used a 80 hi-pinion front third with 5.29's with an ARB, turning 35's. I had Longfields and stock inners. I wheeled that thing all over. I did Rubicon, Fordyce, Moab, Johnson Valley and any other trail that I could find. I never had any problems or breakage on the front axle. I bound up the front tires on more than one occasion, no problems. So I also tend to agree that with poor setup, anything can break, but a proper setup goes a long way.

 

[Tapage]

In my " Tencha " HJ-60 I put in the balance 4.88 or keep my 4.56 and regear my t-case with Low gears ..

I choose the T-case option .. so in 80 series you haven't this option .. But I seen some 4.88 brokes .. not in teeth .. So I haven't any kind of evidence to say are more weak .. coz all that I have seen are broke ousite on the pinion splines ..

 

[Mickldo]

Over here in OZ the 4wd comp guys traditionally don't like the Toyota hi-pinion diff, most run Nissan GQs for their stronger drivetrain. A few of the Toyota die-hards figured out that it is the standard carrier that is the weak link. The large hole to access the star gears weakens the carrier allowing it to distort and flexing the crownwheel. Those running open centres and lockright lockers were breaking r & p but those running aftermarket carriers such as air lockers weren't.

 

[Junk]

Christo's yellow thong isn't exactly your traditional style 80 though.

 

[Tapage]

Those running open centres and lockright lockers were breaking r & p but those running aftermarket carriers such as air lockers weren't.

I thought when you install a Detroit locker or ARB you get a plus ( off course the locker ) with the carrier .. and strongest 3rd member ..

 

[ginericLC]

Another thing is a lot of the 5.29 breakage is from folks with semi floating axles that grind the teeth to get the C clips back in. Just something to think about when you are comparing rumors on gears.

 

[locrwln1]

I thought when you install a Detroit locker or ARB you get a plus ( off course the locker ) with the carrier .. and strongest 3rd member ..

With the ARB...yes, not so much with the Detroit. A lot of guys that have had a Detroit in the front and then break a birf or inner axle have had the shock load take the Detroit out as well. The ARB tends to be able to absorb the shock load without any damage.

Jack

 

[CreeperSleeper]

Also to consider is the quality of gear set you are running. I.E.- Toyota gears are probably stronger than no-name gears.

 

[Tapage]

Another thing is a lot of the 5.29 breakage is from folks with semi floating axles that grind the teeth to get the C clips back in. Just something to think about when you are comparing rumors on gears.

are not posible to fit 5.29's in a semi floating axle .. you must need Full floating axle ..

 

[Junk]

Also to consider is the quality of gear set you are running. I.E.- Toyota gears are probably stronger than no-name gears.

I seriously doubt Toyota is making their own gears.

 

[BenMara]

are not posible to fit 5.29's in a semi floating axle .. you must need Full floating axle ..

back from the dead ^^^^is the above TRUE??

 

[therealratfink]

Nope, Its not true. Did it myself with ZERO grinding of the teeth. Even posted about it.


EDITED TO ADD LINK

https://forum.ih8mud.com/80-series-tech/175070-you-do-not-need-grind-5-29-sf-axle.html

 

[Cruiserpoor]

I think alot of it depends on the situation and the driver.. My cousin blew a front set of 4.88 yukons in his fj80 but he is abusive, and he had 7 adults in the cruiser backing out of one of the hot tubs in moab.. So take into acount the weight and traction factors.. I think you can break anything. Lockers, shafts, gears, hubs.. they will all break in the right situation, I dont think it is a matter of which is stronger. I am going to put 4.88's in my 80 and not think too much about it. If it breaks it breaks.. it comes with the territory. When you run bigger tires you put more stress on things that were not designed to have that much stress on them. You know what I am saying... If you are worried about things breaking then dont rally your stuff. I like to drive my cruiser hard, thats just my style. I have blown multiple pinions and birfs, you just have to deal with it or buy dynatrac 60's or get a buggie. But not me, Cruisers RULE!!!

 

[jonheld]

Nope, Its not true. Did it myself with ZERO grinding of the teeth. Even posted about it.

In the rear of mine the installer needed to slightly take down the inside of 1 tooth in order to get the center pin back in. It is outside of the pattern and was literally a few .001s. This is with 4.56 gears.

I had both 3rds out this past weekend so it's fresh in my noggin. They are very heavy, BTW.

I would imagine that a different ratio may or may not need to be shaved depending on the way the teeth line up. Perhaps someone who does R/P setups all day long could comment on this. Do different manufacturers ring gears have different thicknesses? I dunno about such things.