02-06-2005, 01:29 PM
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Best rear end for GTV daily driver with TS engine??
Hello all. What's the opinion here on the best rear end for a 115 GTV road use car? I've heard the 4.10 should allow good road use and driveablility. Is a 3.73 (auto spider) too low a gearing? I'd like to be able to cruise the highways, but still use the powerband of the engine. I'm not going to race the car though. Keep in mind I'll be running this rear end with a Twin Spark engine (148 bhp). Thanks
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74 Berlina (first car--miss her)
94 164 LS (gone too)
83 Spider (alas, gone)
74 GTV (still have conjugal visits at least)
1987 Milano Verde (now in good hands)
Last edited by Storsav; 02-09-2005 at 01:00 PM.
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02-06-2005, 05:10 PM
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you can use an auto spider axle, or berlina auto or whatever, but use an older gearbox with the short 5th gear. used on well, basically standing pedal 1300 engines... like a single carb Giulia 1300 version. also make sure to have about 150 hp. You will love it. A german pal has that. I run a TS in my berlina with the original Berlina 9/41 axle and original gearbag. the german fellow does 150 km/h at less than 3000 revs! Cool!
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02-08-2005, 04:07 PM
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i just put a 4.56 lsd in my '69 gtv. i haven't really run it much, so i don't know
what i think of it at highway speeds. if i put a ts engine in it, what is the expected
experience in terms of revs/noise? any opinions?
john
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02-09-2005, 10:24 AM
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don't know...
here we use the term 9/41, or 10/43 denominating the number of teeth on crown and pinion repectively. Anyway, my berlina has the stock axle ratio, runs a 160 hp TS engine and does 120 kmh at 3200 revs, quiet, and effortlessly!
So: Fine!!!!
Rik
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02-09-2005, 12:31 PM
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I think the automatic spider had a 3.90. It will hard to come by and most expensive. I would use the 4.10 as it would be easy to obtain. The 1300 5th gear is a .85 or .86 but it would raise your revs probably by 500 to 750 depending on many factors and is not a cheap option. If your objective is to obtain a higher speed with lower revs, make sure you also use the correct size tire. The late model spiders use 185/70-14 which is a 24.20" tall. Any reduction in tire diameter will effectively raise the revs of the motor.
Hope this helps.
Zal
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02-09-2005, 12:49 PM
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Well, I will disagree with the rest of the board on this topic. I like the stock 4.56 ratio in my '74 GTV. Granted, I don't drive it on long trips. With 205/55-15 tires, I think it goes about 20mph per 1000 rpm. Alfas are designed to rev, so 4000 rpm at 80 works pretty well.
On the other hand, my Giulietta has the same rear end ratio, but only a 4-speed. 80mph is 5000 rpm or more. That gets old pretty quick!
Erik Wood
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02-09-2005, 12:59 PM
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I'm looking ot run 15's and a 4.10 probably. The Auto spider is a 3.73, which seemed pretty low to me, though I'm not an expert. I like to cruise though. 90 mph at 3500 rpm would be nice. I'm guessing with a 4.10 and 15's and the 148 hp TS engine, I'll be doing 80mph at 3000 rpm. Sound right?
__________________
74 Berlina (first car--miss her)
94 164 LS (gone too)
83 Spider (alas, gone)
74 GTV (still have conjugal visits at least)
1987 Milano Verde (now in good hands)
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02-09-2005, 03:31 PM
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 Quote:
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Originally Posted by Storsav
I'm looking ot run 15's and a 4.10 probably. The Auto spider is a 3.73, which seemed pretty low to me, though I'm not an expert. I like to cruise though. 90 mph at 3500 rpm would be nice. I'm guessing with a 4.10 and 15's and the 148 hp TS engine, I'll be doing 80mph at 3000 rpm. Sound right?
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You can calculate a car's speed as a function of engine revs if you know the rev/mile value for the tire you're running and the overall gear ratio of the car (assuming no losses due to tire slipage on the road surface). A 205/55-15 Yokohama ES-100 has a rev/mile value of 865 accourding to the Tire Rack specifications sheet (Tire Rack have these numbers for all sorts of tire on their website; I assume the number does not account for deformation of the tire by the road surface). If you run the normal Alfa/GTV box (0.79 5th) and a 4.10 rear end, your rear wheels go around once for every 3.24 engine revs in 5th. So, to turn the tire through 865 revs, 1 mile, takes 2802 engine revs. To go 1 mi/min (60 mph) the engine must turn 2802 rev/min (rpm). From here it's a straight proportion. To go 80 mph takes 80/60 * 2802 = 3736 rpm.
One thing to keep in mind when comparing these calculations with Alfa speedo and tach reading is that the Alfa's mechanical gages are not usually very accurate. If you really want to know how fast you're going, try using a handheld GPS unit. To check rpms, I like digital rev counters.
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Bruce Colby
Competition Director, AROSC
'65 Sprint GT (TS race)
'69 1750 GTV (TS street)
'71 Jr. Z (special occasions)
'89 E30 (the dark side)
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'69 1750 Spider (sold  )
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02-09-2005, 04:37 PM
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Did I miss something here? What car did you end up getting? Do tell (include the appropriate pics as well  )!!!
Ted
__________________
Current:
74 GTV
Former :
88 Milano Verde
78 Alfetta Sedan
87 Milano Verde
70 GT Jr. 1300
[URL=http://www.flickr.com/groups/scuderiano/]Scuderia Non Originale Flickr Group[/URL]
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02-09-2005, 08:38 PM
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Bruce darnit you're confounding me!! Does HP not figure into the equation? I would think that the more ponies pushing the wheels, the less rpms necessary to propel the car??? This is why I'm an English teacher.
Ted, Bruce is practically donating his 72 GTV shell and parts to me and I'm purchasing his Twin Spark engine to do the install. The car's in rough shape, but I wanted my car, my way. It will be a total restoration, happily so. I'll post pics as soon as I've actually picked up the car, and payed Bruce his well-deserved money. I toyed with the Verde idea for a while, but I gotta have my GTV. Thanks Bruce!
__________________
74 Berlina (first car--miss her)
94 164 LS (gone too)
83 Spider (alas, gone)
74 GTV (still have conjugal visits at least)
1987 Milano Verde (now in good hands)
Last edited by Storsav; 02-09-2005 at 08:40 PM.
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02-10-2005, 06:51 AM
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The only way power (HP & torque) enters the equation is by allowing the lump (car) to reach the rpm (top speed). If you don’t have enough power to pull 6000 rpm in 5 th gear you won’t reach the equivalent speed. More power will also allow you to accelerate quicker which is one reason I’m thinking of changing.
The other reason I’m thinking of changing from 4.56 to 4.1 is a very un Alfa one. Currently, I can barely get 200 miles on a tank of gas. This gets expensive and inconvenient to have to stop so often on a trip.
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Ken Lee
Oakville, ON
1974 GTV 2000 - Ruby (I'm never selling this one, honest!)
1973 GTV 2000 - Rowdy (or this one I hope)
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02-10-2005, 07:54 AM
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No worries about the Verde, the right person is out there. Best you got what you really wanted (speaking from experience....see Verde for sale and GTV in garage )! Congrats!
I hope you get detailed photos of the process done, I'd love to see them.
Ted
__________________
Current:
74 GTV
Former :
88 Milano Verde
78 Alfetta Sedan
87 Milano Verde
70 GT Jr. 1300
[URL=http://www.flickr.com/groups/scuderiano/]Scuderia Non Originale Flickr Group[/URL]
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02-10-2005, 10:02 AM
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Quote:
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Originally Posted by GTV4EVR
The only way power (HP & torque) enters the equation is by allowing the lump (car) to reach the rpm (top speed). If you don’t have enough power to pull 6000 rpm in 5 th gear you won’t reach the equivalent speed. More power will also allow you to accelerate quicker which is one reason I’m thinking of changing.
The other reason I’m thinking of changing from 4.56 to 4.1 is a very un Alfa one. Currently, I can barely get 200 miles on a tank of gas. This gets expensive and inconvenient to have to stop so often on a trip.
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I've done several of these rearend swaps and have some good mileage data from my '69 GTV which may interest you. With a 1750 (stock), it averaged 26.6 mpg on the highway and 19.1 around town. I changed the rearend to a 4.10 and the mileage want up to 28.9 on the highway and 20.1 around town. The rearend ratios are about 11% different so, if all else remaines the same, the mileage should go up 11% with the swap. On the highway, it went up about 9.6% which is pretty close. Around town it only went up about 5%. I think what happened around town is that I drove in 3rd with the 4.10 when I would have been in 4th with the 4.56.
__________________
Bruce Colby
Competition Director, AROSC
'65 Sprint GT (TS race)
'69 1750 GTV (TS street)
'71 Jr. Z (special occasions)
'89 E30 (the dark side)
----------------------------
'69 1750 Spider (sold )
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02-10-2005, 11:05 AM
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Bruce,
Thanks for the confirmation, it looks like it may be a worthwhile swap. As an aside, did the US 1750s come with a 4.56? I bought my first 1969 1750 new in Montreal and my second one was first sold in The Hague and they were both 4.10 non LSD cars. My current mileage is nowhere near that good. My odometer is off by 10%, and I'm still not getting much over 200 miles to a tank. I'll see what the mileage looks like after the rebuild this spring and go from there. It would also be good to have a first gear that can be used to at least get out of the intersection before having to shift ;-)
__________________
Ken Lee
Oakville, ON
1974 GTV 2000 - Ruby (I'm never selling this one, honest!)
1973 GTV 2000 - Rowdy (or this one I hope)
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02-10-2005, 11:26 AM
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Quote:
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Originally Posted by GTV4EVR
Bruce,
Thanks for the confirmation, it looks like it may be a worthwhile swap. As an aside, did the US 1750s come with a 4.56? I bought my first 1969 1750 new in Montreal and my second one was first sold in The Hague and they were both 4.10 non LSD cars. My current mileage is nowhere near that good. My odometer is off by 10%, and I'm still not getting much over 200 miles to a tank. I'll see what the mileage looks like after the rebuild this spring and go from there. It would also be good to have a first gear that can be used to at least get out of the intersection before having to shift ;-)
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Second, as far as I know all the US spec 1750s were 4.56s. In fact I think all the GTVs up through '74 and spiders from the same timeframe were as well. I think Berlinas always had 4.10s but Supers had 4.56s, at least in the US. Maybe someone has some better data on this and they could post it for us to see.
__________________
Bruce Colby
Competition Director, AROSC
'65 Sprint GT (TS race)
'69 1750 GTV (TS street)
'71 Jr. Z (special occasions)
'89 E30 (the dark side)
----------------------------
'69 1750 Spider (sold )
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