1981 GTV6 - replace transaxle with a Platinum unit? - Alfa Romeo Bulletin Board & Forums
 
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post #1 of 12 (permalink) Old 02-27-2015, 11:04 PM Thread Starter
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1981 GTV6 - replace transaxle with a Platinum unit?

Hello everyone,

I have a conundrum I am hoping you can help me resolve.

I have a 1981 GTV6 that has a fairly bad transmission. 1st gear syncro is completely gone, 2nd and 3rd gear syncros are in bad shape. Just today I replaced the Swepco gear oil I had in it with Red Line, which made a decent difference - gear shifts are a little smoother, however I still need to shift pretty slowly if I don't want to grind the dog teeth gears.

So I've been looking around for a Milano Platinum transaxle, which seems to be the go to transaxle as, from what I have read, it seems to have better gear ratios, keeps the same final drive as the GTV6, and of course has the famous 25% LSD. I have found one at a decent price in very good condition that does not need refurbishing. But I need to give my transaxle in exchange.

Now I have a small doubt about the gear ratios. Being a 1981 model, my gear ratios should be the following:

1981 GTV6 Gear Ratios

First 3.500
Second 1.956
Third 1.345
Fourth 1.026
Fifth 0.780
Final Drive 4.10

Compared to the Milano Patinum ones:

Milano Patinum Gear Ratios

First 2.875
Second 1.720
Third 1.226
Fourth 0.946
Fifth 0.780
Final Drive 4.10

The doubt that I have is that I will lose some acceleration. The engine in my car is a stock 2.5L with no modifications whatsoever. It's a good strong engine with 140k miles, that I think has never been rebuilt.

Will the taller Milano Platinum gear ratios be a too much for my engine? Will it have much less acceleration? Will I have trouble driving quickly up steep hills?

I know the work involved in installing a Milano transaxle in a GTV6, and that doesn't bother me, however I am a bit fearful I will not like the characteristics of the Milano gear ratio setup.

What do you guys think? I am curious to hear about the experiences others have had with a similar swap.

Thank you for reading and for any comments you may have.

Cheers,
Igor
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post #2 of 12 (permalink) Old 03-01-2015, 04:05 AM
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I would think it would be fine, I believe that the later GTV6's came with the same 4.10 that the Milano Silver/Gold's used although you should verify that. That one is the same as the Platinum just without the LSD.

Kevin

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post #3 of 12 (permalink) Old 03-01-2015, 07:43 AM
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All GTV6 (except for 82/early 83: 3.42) and Milano (except Verde: 3.55) had the same 4.10 diff.

Remember that the slightly heavier Milano used the same 2.5 engine and it has no problem with ratios.

The 3.5 first gear is shorter than the Alfetta. It's a silly gear. The Milano ratios will be an improvement. A usable first gear, closer spacing between 2nd and 3rd, same cruise RPM.

You will have zero problems with the Milano ratios. But some advice should be heeded here: the Plat limited slip, unless properly rebuilt and checked, is probably not functioning well. The only way to verify a limited slip is to open the box and check. Also, it was not uncommon for Plat gearboxes to have issues early on, and some Alfa dealerships replaced them under warranty - but remarkably many were replaced with standard non LSD boxes.

This is definitely an example of wise money considering the work involved to remove DeDion etc. I've chased around transaxles before with "known good" and other used units. Know what? Every used gearbox is "good" except when they're not(!). Better to spend a few hundred more and get it checked out and resealed (Permatex gray).

A properly set up LSD significantly changes the capability of the car (in a good way).

Rob
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post #4 of 12 (permalink) Old 03-01-2015, 03:50 PM
Richard Jemison
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Gearing

The later gear ratios were all a compromize to improve fuel economy ratings.
Performance is the looser with these gearsets. That and the isostatic shifter makes the trans less desirable.

Richard Jemison
RJR Racing

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post #5 of 12 (permalink) Old 03-01-2015, 04:04 PM
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I'm going to disagree there: the isostatic linkage - in good condition - is a pretty nice piece of kit and has good shift feel. Might not be easy to retrofit it into an '81 GTV6, though.

As was stated, the Milano Platinum has the same 2.5L and it moves well. With the 4.10 rear end I can't imagine needing shorter gearing on 1-3 on my Milano. As Rob pointed out, a 3.5 first gear with a 4.10 rear is just silly.

You'll be absolutely fine with the Platinum ratios.

Tom

1963 Giulia Spider (1750 engine)
1974 GTV
1991 Spider
Former: 1987 Milano Gold
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post #6 of 12 (permalink) Old 03-01-2015, 05:05 PM
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I have owned a pair of Verde's and now an early type GTV6 and I prefer the early, non-isostatic linkage. It feels a little tighter driving and it is an order of magnitude easier to disconnect for clutch/transaxle jobs.

Ed Prytherch
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post #7 of 12 (permalink) Old 03-04-2015, 10:25 AM Thread Starter
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Thank you all for your comments on this.

After driving the car with the new Redline 75-90 NS gear oil my transaxle shifts much more smoothly than before. This and also the concerns of modifying the car from it's original state (in the past I have modified a 944TS spending many thousands of $... and made the car worse...), made me decide to not replace my transaxle unit. I really like the way the car drives and handles and the gear ratios, and I don't want to "upgrade" something that will certainly severely change it's characteristics.

Just as a note these are the speeds I am hitting at red line:
1st - 27 MPH
2nd - will add
3rd - 75 MPH
4th and above too fast to test on the highway

Thank you all again for your input.

Cheers,
Igor
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post #8 of 12 (permalink) Old 03-04-2015, 10:52 AM
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I prefer the later isostatic shift linkages as well. The action on the early shift linkage has been described as stirring a baseball bat through a bucket of ice.
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post #9 of 12 (permalink) Old 03-04-2015, 11:01 AM
But Mad North-Northwest
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Yeah, if the new fluid helped no point in changing the transaxle.

Note that first gear on the V6 is only sort-of synchronized from neutral. There's this goofy spring-loaded bit on the piece that actuates the synchronizer lockout (34-36 below) and in practice it doesn't work very well. So while it's theoretically a slightly better setup than the Spider first gear, in my experience it's still typical to get a grind if you shift quickly from neutral into first. It's usually best to touch another gear to stop the spinning and prevent the grind before doing that.

RPM vs speed spec for your car in 5th gear is below. If you're reading different (and you probably are) it's either speedo or tach accuracy.
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Tom

1963 Giulia Spider (1750 engine)
1974 GTV
1991 Spider
Former: 1987 Milano Gold
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post #10 of 12 (permalink) Old 03-05-2015, 06:00 AM
Richard Jemison
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Gear ratios

Is this car one of the one`s blessed with a 3.42 R&P rather than the 4.10 R&P?

Regardless, changing from early GTV6 TA to Later involves totally different speedometer settings.

Richard Jemison
RJR Racing

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post #11 of 12 (permalink) Old 04-29-2015, 08:59 PM
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I just purchased a platinum transaxle for our late '85 GTV6. After reading some posts here Im still a little confused on the speedo setup. Can I just install the original (late 85) transaxle speedo pickup/sender into the platinum gearbox and be good? Or do I need the milano sender and amplifier from the car the transaxle came out of? Any advice would be appreciated.
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post #12 of 12 (permalink) Old 09-16-2019, 11:59 AM
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AvorioVeloce.
Hello, I just came across this old post and have the same issue - a GTV6 with a platinum transaxle and no speedo. Might I ask if and how you might have resolved this issue?

Many thanks,

Michael

"I just purchased a platinum transaxle for our late '85 GTV6. After reading some posts here Im still a little confused on the speedo setup. Can I just install the original (late 85) transaxle speedo pickup/sender into the platinum gearbox and be good? Or do I need the milano sender and amplifier from the car the transaxle came out of? Any advice would be appreciated."
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grind, lsd, platinum, syncro, transaxle

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