higher rear axle ratio

The Series 4 Spiders with automatic trans came with a 3.6 LSD rear. Sounds just about right and it's a plug n play.

Great! Thanks for the info. Do you know what years cover Series 4 spiders?

1990-1994 inclusive.

Your GTV most likely has a 4.56 ratio diff today. Going to a 3.6 will be a big difference. The late spiders with manual transmissions had 4.1 ratios, and that's usually the swap people make who want lower rpm's at freeway speeds.

Are you sure you want to drop it as much as 1 full point? Not that I'm questioning or challenging you, but why do you feel the ratio should be lowered by so much?

Yes it does have a 4.56 diff. I am running at 3700 rpm at freeway speeds. During normal driving I fell that I need a sixth gear. I am in the process of installing a turbo and fell that the extra torque produced will allow me to run at a lower RPM.

P.S. My GTV is a hobby and a platform for learning and so I am always glad for positive criticism and feedback.

Man, if you are pulling only 3700 rpm on the freeway, I need to slow down. I'm pretty much always between 4300 and 5K. I know the spedo lies, but perhaps its not off as much as I thought. (Well actuially it doesn't lie right now, it doesn't do anything.) I'm looking to do the 4.1 swap because I do run quite a bit on the freeway and I feel bad flogging the car. It should improve gas milage as well.

Will

I swapped for the 4.1 from the 4.56 in my '74 GTV and am really happy. I still sometimes wish for a 6th gear but not as often. RPM's dropped at least 500 at what I call freeway speeds - 75 mph or so. Keep in mind that the car will not be as quick as with the 4.56. Mileage can be as high as 30 mpg if my foot is not too heavy.

turbo_gtv said:

Yes it does have a 4.56 diff. I am running at 3700 rpm at freeway speeds. During normal driving I fell that I need a sixth gear. I am in the process of installing a turbo and fell that the extra torque produced will allow me to run at a lower RPM.

P.S. My GTV is a hobby and a platform for learning and so I am always glad for positive criticism and feedback.

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My 4.56 rear and stock TX gears (0.79 fifth) gives me almost exactly 20 mph per 1000 rpm. If yours is similar, at 3700 rpm you're doing 74 mph!. That's pretty fast cruisin'!



Robert

Sounds about right. It seems to like to cruise at 3500-3700 revs anyway especially on Rt. 17.

I have a good 4.1 that I would like to get rid of. I removed it from an 83 Spider earlier this year. The axle was quiet. The car was parted due to accident damage.
I am in Columbia SC. It must be picked up or I could deliver it within a few hours drive. I will not ship it.

Ed Prytherch

Southern California Traffic forces one to speed. I find that the average freeway speed is 70 MPH, even in the slow lane. I am just looking for some head room.

Does anyone in Southern California have a 3.6 gear set?

turbo_gtv said:

Southern California Traffic forces one to speed. I find that the average freeway speed is 70 MPH, even in the slow lane. I am just looking for some head room.

Does anyone in Southern California have a 3.6 gear set?

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Yeah no kidding. Last year when I went to my parents place for Christmas, I was on I5 for all of 2.5 miles, and for that 2.5 miles, I was wrung out at 5500 rpm in the slow lane getting passed by semis. Let me tell you the car wasn't happy. Thats probably the reason the original to the car exhaust self destructed just north of Fresno on the way home (ok, it was a little on the rusty side).

Will

Geez, do you have a 3-speed manual transmission or something? Seriously, at 5,500rpm you should be doing almost three digit (my Spider would be travelling at over 110 @ 5,500rpm but I swear that I have never tried it), even if you have a 4.56 diff. The semis in Colorado don't go that fast. I am positive that one (or both) of the meters on your GTV is way off.

BlpltGTV said:

I was wrung out at 5500 rpm in the slow lane getting passed by semis. Let me tell you the car wasn't happy.

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With a 4:56 rear end 5500 rpm in 5th gear is 110mph. Maybe the tach is way off!

"wrung out at 5500 rpm..."
Me thinks BlpltGTV was stuck in third gear!

BlpltGTV said:

Yeah no kidding. Last year when I went to my parents place for Christmas, I was on I5 for all of 2.5 miles, and for that 2.5 miles, I was wrung out at 5500 rpm in the slow lane getting passed by semis. Let me tell you the car wasn't happy.

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Speed limit here is 55 mph on our"major" roadways (we have 2) and , I don't care how fast you're going, fact is, someone's gunna pass you

On my Giulietta Spider with the current 4.56, 4000 calculates at 74 mph, and 3500 at 65 mph.

With the soon to be installed 4.1 the numbers are 82 mph and 72 mph.

So the rpm at cruising speeds is done at almost 500 rpm lower.

Also, it will make third and fourth more effective.

Sounds like a worthwhile modification IMO.

Oooops--forgot another big plus--the 4.1 has a lsd.