[bouttell]

Hi all,

my name's Luke, first time posting on this forum. Recently bought a '87 Sierra 1.3l manual. I'm looking at upgrading to a g16b to get a bit more power out as I'll be doing a fair bit of highway driving. The current gearbox is making some pretty funky sounds in 3rd and 5th and I've found a Vitara G16B with a manual gearbox.

Could someone confirm whether or not the Vitara 5sp gearbox is an upgrade over the Sierra 5sp box? I did a bit of a search but couldn't find a straight answer.

I did find I'm going to need to make a gearbox cross member, shorten the jack shaft and open up the tunnel. Are there any other key changes I need to be aware of? And can anyone elaborate on how much the tunnel needs to be opened up by?

Also if anyone has handy the differences in gear ratios it would be appreciated.

[Gwagensteve]

Gear ratios are the same/close enough. Gearbox is stronger but most importantly uses a much better clutch.

[rexhunta]

it needs about 30-40mm per side of the tunnel to be opened, I had a look at doing the SJ51 the other day.

[ZUZUKI]

Obviously with the box out & on a hoist makes it easier, but with careful belting using a lump hammer, quite an even and respectable result can be had - the tunnel (like all Sierra panels) is quite thin.
If you set the engine low in the bay (helps for bonnet clearance as well) it's an easier fit.
The gear stick will need to come out about 1/2 way down the ramp of the tunnel & the original hole plated over.
Lots of Sierra boxes feel a bit ropy and not just in the bush, where the average Vitara box is still a good thing.
Rgs, Michael