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Engine Specific Info and Questions => IDI Engine => Topic started by: Monoaural on November 02, 2012, 05:13:46 pm
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Found a transmission out of an 79 diesel. Code FF, but I found that is not the same a later FF, and revs ~200rpm higher than my stock GP.
I commute 120 miles a day, but would like a five speed for a bit better acceleration. Worried that I will lose some MPGs, at the expense of better acceleration. Also worried about adding some roughness at 55-60mph that I cruise at. Keep it stock with the lower geared 4spd?
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Found a transmission out of an 79 diesel. Code FF, but I found that is not the same a later FF, and revs ~200rpm higher than my stock GP.
I commute 120 miles a day, but would like a five speed for a bit better acceleration. Worried that I will lose some MPGs, at the expense of better acceleration. Also worried about adding some roughness at 55-60mph that I cruise at. Keep it stock with the lower geared 4spd?
i would just leave the GP in there..
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So the GP trans is the 3 + E one that means you are running this combo GP (3+E from '81) 3.89 3.45 1.75 1.06 0.71 RP first number, High of .71 for E mode.
Switch it to the FF of non mid 81 vintage and you go here, FN, FF, FH (most to 7/80) 3.89 3.45 1.94 1.29 0.97 0.76 If you are moving at 55 to 60 for most of the trip you will add RPM to the engine and thus give up the "tall" gear. That won't buy you mileage if on the flat and level.
If you are like me I need that drop down to 0.97 once in awhile to pull hills at 55-60 without winding the engine to its limit.
You have probably explored this: http://scirocco.org/gears/ to figure out the RPM differences at the top end but how about the next gear down? That might help you decide.
I would opt for the 5 spd over the 4 but then I always one for more is better kind of thing.
DAS
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So the GP trans is the 3 + E one that means you are running this combo GP (3+E from '81) 3.89 3.45 1.75 1.06 0.71 RP first number, High of .71 for E mode.
Switch it to the FF of non mid 81 vintage and you go here, FN, FF, FH (most to 7/80) 3.89 3.45 1.94 1.29 0.97 0.76 If you are moving at 55 to 60 for most of the trip you will add RPM to the engine and thus give up the "tall" gear. That won't buy you mileage if on the flat and level.
If you are like me I need that drop down to 0.97 once in awhile to pull hills at 55-60 without winding the engine to its limit.
You have probably explored this: http://scirocco.org/gears/ to figure out the RPM differences at the top end but how about the next gear down? That might help you decide.
I would opt for the 5 spd over the 4 but then I always one for more is better kind of thing.
DAS
the only thing about the GP and 4A trannies, is that they have a HUGE jump between 3rd and 5th, er, i mean, 4th gear..
driving a 4A/GP is like driving a 5 spd, with a blown up 4th gear..
GP/4A would be BOOBS with a gear in between 3rd and 4th..
so, you are losing speed going up the hill in 4th, then you shift 3rd, rev up to about 5500, and still dont have any power, because you are past where the governor starts cutting fuel..
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so, you are losing speed going up the hill in 4th, then you shift 3rd, rev up to about 5500, and still dont have any power, because you are past where the governor starts cutting fuel..
Gov mod time... ;)
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i would just leave the GP in there..
*2
i didn't gain too much with a post 5/79 FF over the GP; seemed like i was always shifting with the 5 speed and the GP is actually better on hills up to 55mph or so.
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Gov Mod it is.
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I loved my GP so much, I left it sitting in the dirt the day I left the farm.
Sure wish I would have grabbed reverse out of it. And, the flanges.
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FF. Even if it isn't the highest geared FF, the flexibility of the other gear for hauling a loaded car up a hill is more than worth it. Later FF can cruise at 65 mph in 4th all day (similar gearing as the GC that my car has, except FF has an added 5th for comfort and economy). In the end, unless you're driving at the economy sweet spot for a 1.6, which I've heard is around 3400 rpm, (85mph on a GP vs. 80mph on an early FF with 185-65-14), the taller top gear ratio isn't going to help too much, and may hinder comfort and economy.
But if you're anything like me, you'll take everyone's advice, disregard it, and do whatever you feel like because you're free to make your own mistakes. That's the magic of the internetz.
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FF. Even if it isn't the highest geared FF, the flexibility of the other gear for hauling a loaded car up a hill is more than worth it. Later FF can cruise at 65 mph in 4th all day (similar gearing as the GC that my car has, except FF has an added 5th for comfort and economy). In the end, unless you're driving at the economy sweet spot for a 1.6, which I've heard is around 3400 rpm, (85mph on a GP vs. 80mph on an early FF with 185-65-14), the taller top gear ratio isn't going to help too much, and may hinder comfort and economy.
But if you're anything like me, you'll take everyone's advice, disregard it, and do whatever you feel like because you're free to make your own mistakes. That's the magic of the internetz.
That high, really? :o I would be interested in reading that information; I would've thought it's more like in the low to mid 2000s, at peak torque. But then again, maybe it's the aerodynamic drag from pushing all that air at 85mph, and not the high revs, that's detrimental to fuel economy ???
As for the transmission, I guess it would depend on what motor it's paired with. If you're turbocharged, I'd leave the GP in there. If not, I'd go with the FF.
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Guys, keep it simple.
If you have the option a 5 speed is always better. If you want a 4 speed then you can skip 4th gear every shift. The FF is one of the better trans VW ever offered gear wise. All around it is great, for me personally I would like it better with a 3.67 ring a pinion, but as is it is a great trans. I drove the 4 speed in my old 84 flat red bunny and it was horrible...but I live where there are tons of changes in elevation and there were no good spots for gearing in that trans.
It comes down to personal preference and your personal preference should be the 5 speed if you have both trans laying there.
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You need more torque from your engine. So you can then take any 020 and have your way with it on the hills ;)
I can pull hills at near idle in 5th on my ACN :D!
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Clearly you ain't got squat for hills there.
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Clearly you ain't got squat for hills there.
Not mountains, but I do have well over 150ft/lbs of torque at 1900 soo it helps a little ;)