When, and why should you fit a tail shaft spacer?

A 4WD is made up of a huge number of components that work together to give you a vehicle that can be taken where normal vehicles cannot. It only takes a few modifications or changes to upset these components though, as we very quickly found out with our Dmax tail shaft.

We had it for a few months, and in the process of the Dmax build we identified the need for a GVM upgrade. This was done by ARB in Canning Vale, and it increased our maximum GVM to 3220kg, which was fantastic.

Dmax GVM upgrade
Our 3220kg Dmax GVM Upgrade

However, not long after we started to have a minor weep, and then a leaking transfer case on our Dmax, which was frankly a pain in the backside. I looked at a number of different reasons for this, and spent a fair bit of time working with Isuzu and ARB.

Originally Isuzu replaced the seal out of good faith, but said that it was due to the lift kit and the angle of the differential. You could clearly see that the tail shaft was sticking out further from the transfer case, so there was really no leg to stand on.

A leaking transfer case
An annoying transfer case oil seal leak

However, after going through a number of seals, I was getting pretty tired of things, and got back in contact with ARB. They agreed to install a tail shaft spacer, and I went to the workshop and helped put it in.

The gap on my tail shaft was allowing enough space for dirt and grime to get in, and I’m positive that the dirt was sticking to the shaft, and slowly making the seals leak. That, and the bush that supports the tail shaft inside the transfer case would have less meat to support it, so it was a losing situation on both ends.

Ironman actually make a tail shaft spacer for this, that is designed to ‘stop oil weeps’, and ARB were good enough to purchase it, and install it.

During the install, we made sure that in the event of significant spring compression there would ne no chance of the tail shaft going too far into the transfer case, and this was pretty clear. As the springs go up, the differential moves backwards meaning there really isn’t a huge amount of movement in the tail shaft anyway.

The tail shaft spacer of around 10mm was fitted, and a new seal was put in not long after, and we have had no issues since. Now, some of you might notice the nuts are around the wrong way in the below photo, and that is intentional, and as per the fitting instructions from Ironman. 

You actually can’t install them the other way around as the extra flange on these nuts fouls on the steel, and causes a problem.

Tail Shaft Spacer
The 10mm Ironman Tail Shaft Spacer

However, there is one caveat here in regards to the transfer case seals, and that’s the actual seal location. Isuzu have made a bit of an engineering mess up when designing their transfer case, and it allows the tail shaft seal to be installed further than where its actually meant to sit.

We’ve written about this before, but when you replace the transfer case seal you can knock it in about 6 – 7mm before it comes to the end of the housing, which is what most people would do. 

If you do this though, you’ll end up with a leak almost straight away as the manual specifies 3 – 3.8mm gap. I’ve heard of a lot of dealerships and mechanics getting caught by this, and a part of me wonders if the seal was put in the right location to begin with perhaps I’d never have gotten a tail shaft spacer.

That said, it does put the tail shaft back where it was, and protects it from dust ingress better so I’m happy with it.

Dmax transfer case
Watch how far you knock the seal in!

If you are going to install a lift kit, pay attention to the position your tail shaft is sitting in, and then measure it again when the lift kit is in. If its moved out a lot, you’d be wise to consider fitting a tail shaft spacer!

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