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#15
by
burn_your_money
on 31 Jan, 2007 19:02
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One thing I don't get: the gasser trannys have taller gears than the diesels. Why?
I think it is because they rev higher and make more power up top
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#16
by
Northboundtrain
on 01 Feb, 2007 22:40
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[quote="burn_your_mooney]I think it is because they rev higher and make more power up top[/quote]
What?
Gas engines rev higher and make peak torque at a higher rpm, so the gears should be shorter on gas engines. Doesn't make sense to me at all.
I'm kind of curious why VW did this.
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#17
by
jtanguay
on 02 Feb, 2007 00:22
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well if you look at a 52hp motor vs a 100 hp motor, the 100 hp motor can have taller gears and still accelerate quite quickly... put that same tranny in a 52hp motor and... slow accel.
those big yellow school buses have really low gearing... bad for highway mileage but they can really zoom up to 50km/h where they normally cruise around town... get it now?
its not really until the turbo diesels which achieve more torque at lower rpm's that vw installed some really nice tall tranny's...
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#18
by
Northboundtrain
on 02 Feb, 2007 08:00
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Yeah I get it. But it makes you wonder what VW was thinking if they made an engine so underpowered that they put in trannys that required reving to nearly 4 grand just to go down the highway. Kind of defeats the purpose of the diesel engine.
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#19
by
jtanguay
on 02 Feb, 2007 09:17
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Yeah I get it. But it makes you wonder what VW was thinking if they made an engine so underpowered that they put in trannys that required reving to nearly 4 grand just to go down the highway. Kind of defeats the purpose of the diesel engine.
tell me about it... my current tranny has to be a swap in from a different type of motor, as even andy2 was saying the gearing is too tall... 3200 rpm gets me to about 100km/h or 60 mph... it just plain SUCKS... back my fuel!!! argh :lol:
but i never have to downshift.. my old jetta i had to on a couple of long steep stretches... but my old jetta also did 160km/h @ 3800 rpm...
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#20
by
VWCaddy
on 04 Feb, 2007 16:30
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One thing many of the NA diesel transaxles have is a very tall 5th gear. So that makes up for the final drive, giving a 2.77:1 ratio in 5th on the FN transaxle for example. I have a 2.57:1 ratio with my rebuilt FN (3.67 final drive and 0.71 5th gear).
You get the lower overall gearing in 1st to get going, since all the 020s seem to have the same 1st gear ratio (3.45). Ideally you would also like a 6 speed tranny for the diesel, since they can't rev as high, nicer to have more gears spaced closer. Also have to consider that the US speed limit was 55 for much of the time that the early diesels were designed for this market. I know my old '81 did really well @ 55, but when the speed limits went up to 65 it struggled a lot more and MPG fell.
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#21
by
craiggroombridge
on 04 Feb, 2007 17:48
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but i never have to downshift.. my old jetta i had to on a couple of long steep stretches... but my old jetta also did 160km/h @ 3800 rpm...
and what was this jetta my 86 gasser goes 160 at 5000 rpm tell me where do i find this 160 at 3800 (german autobaun) trans
Craig
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#22
by
jtanguay
on 04 Feb, 2007 19:29
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hehe i can't quite claim 3800 because the car didn't really have a tachometer... i was mainly going by engine sound... the car still had plenty left and let me tell you... the turbo in that thing ripped! it did 120km/h with ease... 100km/h was hard to hold because the turbo would start to kick in and start doing around 110km/h and if i didnt watch it, it would creep up to 120km/h where it loved to cruise at.
mechanical lifter is definitely more powerful.
and the turbo must have been a garrett T3... very laggy though... wouldn't come on till 3k rpm or so. (again im just judging by engine sound... but i am a pretty good judge of engine sound/noise)
i believe it was either an ACL or ACN. ACL came with 100mm axle flanges... it was a '86 Jetta GL no a/c... no PS... i loved it!!!!!! get popey arms pretty quick lol... less to break IMO
the sheet says that the ACL or ACN will do 160km/h @ 4000rpm so I wasn't terribly off
i recently bought a nice CHE trans with the 0.71 5th gear fitted... now that tranny will do 100mph / 160km/h @ 3800
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#23
by
Northboundtrain
on 04 Feb, 2007 20:28
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So can anyone turn me onto a good tranny rebuilder? I have an old 5 speed that came out of a A1/MK1. Will I be able to send it in as a core for an ACN?
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#24
by
VWCaddy
on 04 Feb, 2007 21:51
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German Transaxle in Bend Oregon is decent:
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http://www.gtainc.biz/(looks like they may be having some web server problems right now)
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#25
by
Northboundtrain
on 10 Feb, 2007 07:48
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#26
by
janb
on 12 Feb, 2007 14:42
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you can usually be ok with a used gas tranny, as they willl outlast (gas) engine ~ 3 to 1, and the 'cruiser' trannies are less likely to be hammered (not GLI / GTI) You can switch 100mm flanges to 90mm, or use the 100mm shafts. I built a spring compression tool from threaded rod that enables the flange swamp pretty easy. A starter bolt and some shims will work.
Your stock Diesel trannie is in big demand with gas racers, they will usually trade you 2 gas trannies for one diesel with your huge Ring gear. Vortex is a good spot to get trannies, or a local 'u-pull-it', or buy a dead gasser and part it out
The reason VW put this gearing in the '91 and '92 was to meet emission requirements (and they cut out the fuel enrichment on the TD. ) Mine seem to get better mileage running high RPM... but its not good on the ears.