Technical Stilo JTD/Multijet 5-speed to 6-speed gearbox upgrade?

[Dee H]

Hello,

I own a 2005 Stilo multijet with the 192.A.8000 engine (120 hp). It has the 5-speed GETRAG gearbox.

The 1.9 16v multijet 192.A.5000 (140 hp) has a 6-speed gearbox. Can I upgrade my 120hp 192.A.8000 with that 6-speed gearbox? I would assume it's possible since the engine block is essentially the same. Can anyone confirm that?

I believe this kind of swap is possible on Alfa 147s. Is the same true for the Stilo?

 

[Ralf S.]

What's the objective? Have you checked the ratios?

Sometimes a 6-speed box only has a slightly higher 6th than the 5-speed box 5th gear it replaces - it's just the intermediate gears which are more closely spaced in the 6-speeder. If you just wanted a longer top gear, then the improvement might not be as big as you think.

Otherwise, I'd expect it should fit... but I dunno. Interesting project though..

Ralf S.

 

[Dee H]

Hi Ralf,

Thanks for your reply. I confess I had not checked the ratios yet. I just looked it up in elearn (see attachment) and it does seem that the final gear ratio is pretty close between the 5-speed and the 6-speed. So it looks like you're right in thinking there might not be that much to gain economy wise..

The reason I was considering the swap is that I'm looking into buying a second diesel Stilo and the one I have my eye on (a 115 bhp JTD) looks to be in great condition (cosmetically) but according to the owner it has recently developed a problem of not wanting to go into 1st, 3rd, and 5th gear. So I was thinking that, should the box need to be replaced (it could also be a clutch or cable issue), then I could try and fit the 6-speed. I mean, why not give that a try, right? The experience I have with the 6-speed gearbox in my 1.4 16v (95bhp) Grande Punto is that the 6th gear makes a big difference in RPM and fuel consumption at motorway speeds. Heck, I even use it in town when driving down long lanes at 50 kph.

But then you make a good point in saying that the 6th gear is not always longer, sometimes the gears are just closer together. And that seems to be the case here.

However, if it turns out that I need a replacement box then I might as well try and put a 6-speed on. Do you think the axles will be a different length, 5-speed versus 6-speed? I would assume they're the same, to keep production costs down. Differential should be the same on both boxes, right? And the distance between the diff and the hub/knuckle determines axle length so I'm inclined to think they're the same length for both gearboxes. That would just leave the shifter assembly to swap over.

 

[Ralf S.]

In that case.. yes, sounds like a plan.

The 120bhp has the same gear linkages and driveshaft part numbers, so assuming that the bell-housing fits to the engine itself, the rest of it looks like you can use your existing 115bhp components. I imagine the 120 does not have the 6-speed box however.

The 16V engines are a different kettle of fish. The 136 (Belgium), 140 and 150 engines have different part numbers than the same component on the 115, so they're likely to be more problematic... although not necessarily impossible to adapt. There's no hard and fast rule.. the 136 and 150 are the same in some respects but different in others to the 140, while the 140 and 150 might share parts that don't fit the 136 .. the only common feature is that none of them share parts with the 115.

Obviously the parts might work +/- some 140/150 parts from whoever sells you the gearbox but you might have to swap too many parts to make it worth your while, unless it's just a hobby and it doesn't matter if you can't make it work. The best example is the front wishbone arms.. the later cars are stamped rather than cast items and they can only fit to the earlier cars if you also fit the front sub-frame. It's possible... but maybe not the simple swap you imagined.

Unless someone has done it and knows differently, obviously..

Meanwhile... pop the gear cables off the ball/knobs on the gearbox selector and make sure they both move freely. The rubber gaitor will be long since perished and the cables point slightly uphill, so collect "splash" which can drain into the cable. Stick some grease down the cables (lithium is best since it won't dry out and turn stodgy) and see if the inner cables move freely.

The cable ends can be unbolted if they're worn and the socket doesn't stay on the "ball"... so you could buy cables from a breaker (or new cables) and just remove the ends and fit them to yours.. It's a lot easier than replacing the entire cable if the rest of it is good.

Ralf S.