Thread: r380 strength on paper vs reality

Most will say the Auto,s are crap as well . Both will handle the power if driven sensible but who drives like nana with all that power on tap anyway .
Honestly both the auto and R380 die behind a rover engine diesel or petrol .
Ive had a lt77 in a rangie with a injected 4.4 and that lasted for years
The end of the day its your call good luck with the choice

Originally Posted by brend0n

I know there are heaps of topics regarding this but need to clarify

on paper this combination works.
last Holden 5Lt (stock VT commodore) 304nm

R380 are supposedly rated to 380nm, so on paper this combination would work fine.

however there doesn't seem to be many/any people running this combination. Is it because of all the suggestion that its not a strong box or most people prefer an auto?

If driven normally, on paper at least, this seems to be a workable option? or am i missing something

As indicated above, if your driving style is smooth an R380 will last for 100s of thousands of Ks, a much stronger and more reliable box than the LT77. If you want to do wheel spins at traffic lights and go like a mad thing at every obstacle off road, the box will die in short order.

With the sort of power the Holden donk has you don't need to go mad, mostly you can use the torque of the engine to idle over things.

The down side of the R380 is the low oil volume to dissipate heat, so off road an external cooler and added volume will increase the reliability of the transmission. Remember in Europe the disco R380 don't have the external cooler but they are usually fitted in Oz and South Africa etc. You can always increase the size (therefore the oil volume) of the cooler, which allows the oil to do its job.

Not all R380s were created equal
The earlier R380s were rated at 380nm but the later suffix L has had significant upgrades and from what I understand Ashcroft rate them at about 440nm.
I may be wrong but thats what I have read in the past maybe Dave or Ian can correct my statement if they read the post.

Plenty of people seem to trash 5th gear when towing suffix L or otherwise.

I don't know about Ashcroft rating the late suffix R380 higher than 380 Nm, but they do have good information about the problem with the early R380 and later improvements.

On paper they are much stronger than the LT77, and I would be very confident that apart from the mainshaft problem with the early R380, that would be the case.

Gearbox strength is affected by many factors and wear reduces strength of gearboxes.

Lubrication also affects the strength of gearboxes. Lubrication is one of the factors used in determination of gear ratings in the AGMA (American Gear Manufacturers Association) and SI gear rating standards.

I put quite a few km's on a R380 in a late Disco I, and they were not hard km's at all. What I found is they run very hot and the oil deteriorates, needing changing at quite short intervals.

I changed to fully synthetic Castrol Syntrans from early on, but still needed lowish oil change intervals. The Disco didn't have an oil cooler, which would have helped.

When bearings develop wear (possibly due to poor lubrication), the tooth loads are not distributed uniformly across the width of the teeth and thus the strength is greatly reduced.

Wear of gear teeth also increases the dynamic loads (the cause of noise from gearboxes) and thus reduces the strength.

They are a small gearbox, and the saying about asking a boy to do a man's work rings load.

I would think a good, late suffix R380 with an oil cooler and synthetic transmission fluid, would stand up to a 5 litre Holden engine. I wouldn't entertain one behind my Isuzu 4BD1T however, that would be a recipe for failure.

I broke the layshaft in a suffix L (late one), but having said that I don't really have any concerns about there strength. (I think all the damage I did occurred while in Reverse too although it failed while in 5th)

If you want to be sure get a td5 era r380 and upgrade it with the modified rear housing and larger bearings from Ashcroft, along with the oil coolers already mentioned.

I don't think you would break it then unless you were really trying too.

Given that an R380 is supposed to be stronger than an LT77 and I haven't broken my LT77 yet, they must be pretty good. My LT77 has (I suspect) been rebuilt at some stage (prior to my ownership). It has survived about 8 years of my use, 4 of those behind a 3.9. I drive it hard, but I don't shock load it or tow heavy loads at slow speeds in 5th gear.

When talking about the LT77, you need to be careful. There is a huge strength difference between early ones and late ones. You need to make sure you look at the suffixes first.

I'm not convinced a late model LT77 and much difference in "strength" than an R380.

I looked at the R380 to fit to the Isuzu in my county and I contacted ashcroft with a few questions about the upgrades they sell
I looked at the quaife gear set and its rated alot better than the standard R380 stuff and I think if I had money to burn I would give this set up a shot
But being poor and having the ability I have now crafted my own adaption of fitting an Isuzu truck box which is way stronger and has better ratios for what I am doing

If its strength your after have a look at what we made fit into my brothers 110 county in his build thread cal415's 110 county build up thread in members rides

The Nissan box to LT230 is a good set up and has plenty of strength to take 500KW and prob 800NM as I would say that the county gets near them numbers by my seat of the pants O meter