GTV6 gearing - Alfa Romeo Forum
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(Post Link) post #1 of 8 Old 05-06-06 Thread Starter
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Help GTV6 gearing

Hi there, I have a GTV6 converted with 3.0 litre engine and twin spark 75 gearbox with lsd. She is running on 164 15 inch alloys with 205/ 50/15 tyres. Because the car has no speedo (was built for Alfa Championship and this was considered surplus to requirements!! weight saving gone mad!) I can't be too sure what speed I'm doing. However, when I picked the car up last week, follwing my mate on motorway he signalled he was doing 70mph and stuck to that speed for several miles.
At this point my rev counter was reading 4900!!!!!!!!!!!!!!
Red line shows at 6000!!. Does this sound right?
I know it lowers the gearing with the twinspark 'box but I didn't expect it to be that low.

Any thoughts??
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Re: GTV6 gearing

Your tyre/wheel combo isn't too far out, so the gearing should be about 22mph/1000rpm in fifth for the TS box. Check your rev counter against a timing gun or similar.
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Re: GTV6 gearing

I have the standard motor still in the GTV6 but I have the TS LSD Gearbox in my beast.
Post some photos of the beast....
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Re: GTV6 gearing

[QUOTE=Barbalatte]I have the standard motor still in the GTV6 but I have the TS LSD Gearbox in my beast.
Post some photos of the beast....[/QUOTE

Which is it ? The engine i mean you said it had the 3.0 then you stated it still has the original motor. Also you did not state which gear you were in i presume 5th.

my gtv with standard box i think with 3.0 does about 3500 rpm at 110ks which is close to 70 i think, someone may have played with your diff
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(Post Link) post #5 of 8 Old 06-06-06 Thread Starter
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Re: GTV6 gearing

I believe it is a 3.0 litre from a 75. Yes I was in fifth gear.
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Re: GTV6 gearing

Sounds like theres something odd there!

I've got my alfa 75 owners handbook in front of me which gives me the roadspeeds per 1000rpm in fifth gear.

1600cc =30.7km/h(19.18mph)
1800cc =32.5km/h(20.31mph)
2000cc =32.5km/h(20.31mph)
2500cc =34 km/h(21.25mph)

I'm afraid the figures are for the first generation of alfa 75 so do not cover the twin spark or three litre but shows that youre car is much lower geared than even the 1600 so something is amiss.Youre car equates to 14.28mph @ 1000rpm.

Hope this helps anyway.
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Re: GTV6 gearing

Hmm, my 3.0 GTV6 does around 145 mph at 7,200 revs in fifth (not on the road obviously, it's not registered) and the 2.5 does around 3,000 revs at 60-65 (it's been a while but the resto is nearly finished). The 3.0 75 is geared around 3,000 revs to 75 mph or so and the TS has the same gear ratios but a different final drive and is a popular mod with quick shift linkage on the V6s for more speed. The figs you got do suggest something amiss somewhere, or some seriously low gearing!!
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Idea Re: GTV6 gearing

Captkirkham, do you have an idea if the 4900 seems realistic or not? Surely you have an idea if the engine is actually spinning at that speed or not? (I'm not trying to criticise you BTW)

My first thoughts are that there is a mismatch in the rev counter componentry, and that there is a mix between the gubbins for a 4 and 6 cylinder engine. My thinking is that with that size of tyre, 70 MPH should be around the 3300rpm mark which is close to 4900/6*4 or simply 4900/1.5. This thinking would indicate that the rev counter is actually for a 4 cylinder car.

BTW, the 75 TS should be geared 20.9 per 1000 in 5th with 195/60R14 tyres which are slightly larger than the 205/50R15 size you have.

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