What Gearbox will fit?

[3cav3]

I think the problem is the gearing, 5th gear doesn't bring the revs down low enough on the V6 in my opinion.

Could you squeeze in a later 6 speed box out of say an Astra etc.

[Robsey]

I presume you mean from an astra-h
(2003 to 2009)?

I think that is the M32 box?

The astra box is laid out brilliantly, but has one weakness - one of the bearings in the box is made from fudge, and can wear / fail quite quickly.

I have noted that the later engines can be mated up with an F17 gearbox...
And I have seen an Astra-H Z20LEL engine grafted onto a Cavalier, so I am sure the answer is yes.

As long as you have a big block (family 2) engine. 1.8, 2.0, 2.5, 3.0 and the 1.7 diesels.

Sadly that rules out 1.4 and 1.6 (but not C16NZ2 if I remember correctly).

Not sure, but it may need a little ingenuity on the engine mounts...

[3cav3]

Ive come to the conclusion that the berring you mention fails when it overheats after continuous use i.e motorway . My first Astra h the gearbox failed at 100000 miles and was replaced under warranty. My second one is still on its original box at 136000 miles and still going strong. it's used mainly on fast b roads and a roads with occasional motorway use.

[Robsey]

In real terms, a gearbox should easily exceed 150,000 miles.

My F18 has passed 275,000 miles on the original transmission fluid.

So 100,000 is very poor for a modern gearbox.
Unless you are a boy racer of course.

[3cav3]

The one that failed was done under the previous owner. I've heard they are prone at failing at very low mileage. I've had gearboxes still going strong at 400k+

[James McGrath]

I think the problem is the gearing, 5th gear doesn't bring the revs down low enough on the V6 in my opinion.

Could you squeeze in a later 6 speed box out of say an Astra etc.

The popular choice for the V6 is the F25/4 out of the Cavalier turbo. Not sure that that will actually be any better for getting the revs down, probably the opposite.

It's a personal preference thing really, I just think a really overdrive 5th would have suited the engine.
In 5th gear, this is what the engine revs at approximately:
50mph - 2000rpm
60mph - 2400rpm
70mph - 2800rpm

Some may say that is quite tame enough already, I'm just used to the crazy gearing of the 2.0i 8v Cavaliers where the engine just ticks over at 2000rpm at 60mph.

[Robsey]

Agreed -
The revving at 70 of the cavalier sounds a bit harsher than our 6 speed (M40 box) Vectra-C.
The Vectra purrs along at 70 mph at 2000 rpm.
All very chilled and refined.

I think the Cavalier is nearer to 3000 rpm on my C20NE with F18 gearbox.

Troy (BTCCTroy) keeps telling me to swap to an F16 with wide 5th gear.
But then, he also tells me to put a C20XE in too.
I am happy as I am until something in the box eventually goes pop.

[James McGrath]

I've got the F16 wide ratio box on my Diplomat with 15" wheels too.
Revs at a civilised 2300 at 70.