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 LittleRalph
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| posted on March 10th, 2003 at 09:09 PM |
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Changing Final Drive Ratio
I read a post recently where someone was after lower ratio gearing for a Manx with big rear wheels and final drive ratios were mentioned.
I have the opposite problem. I have a stock 1300 with 14" wheels and tyres. (I think they run about the same outside diameter as the original
15".) My run to work and back each day is about 90% freeway at 100 km/h. I don't have a tacho so don't know the exact revs but it
sounds like it doesn't want to go much further.
How much hassle is it to increase the final drive ratio in the box or am I better to just get a 1600 box and slip it in?
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1303Steve
A.k.a.: Steve Carter
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| posted on March 10th, 2003 at 09:44 PM |
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Hi
The cheapest solution would be to use taller wheels & tyres, the other solution would be to change gear ratios, either fit super bug or L bug
internals into your box or you could buy an overdrive 4th which leave you with a huge gap between 3-4 or just buy earplugs or a good stereo.
1302Steve
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Woozy
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| posted on March 10th, 2003 at 10:35 PM |
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Also remember that whatever you do the 1300 isnt going to like sitting any more than 100 kmh for real long either.
How hard is it to get late model gears into a early box (60 ish) I run my baja mostly on road and would like to have a little more top end as she tops
out (full revs aprox 5k in 4th) at what i guess is around 140 kmh tho the speedo only goes to 80mph.
My current gearbox is on its last legs so i will be looking for a better solution soon
:vader
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I belive i shall have a beer !
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aussiebug
A.k.a.: Rob Boardman
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| posted on March 11th, 2003 at 01:25 PM |
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The 1300 box has a 0.89 4th and 4.375 final drive for about 3400rpm at 60mph (100kmh).
The engine might SOUND busy but it's quite happy up to 4500rpm all day long so you are NOT taxing it by running at 100kmh all day long (the VW
Owners Manuals all say that top and cruising speed are the same - meaning that the engine can stand running at full speed continuously)
The 1500/early 1600 boxes use a 0.89 4th and 4.125 final drive for about 3200rpm at 60mph (100kmh). This final drive changes every ratio in the box,
so acceleration with the 1300 might suffer and you might have to use the lower gears more.
These final drives are a straight swap, but not necessarily a handiman job, unless you know what you are doing with gearboxes.
The later gearboxes (73 upwards) have a 0.93 4th and 3.875 final drive (about 3050rpm at 60mph - 100kmh) and these are not a straight swap (but can be
done with more extensive work).
Steve suggests bigger diameter tyres and this WILL work to drop the rpm a little, but if you put larger tyres on the front the speedo will under-read
and the cops will LOVE for for the revenue you provide :-)
The normal diameter of 165/15 tyres is about 24 inches - so if your 14" rims have tyres with less than 24 inches Dia then your engine will be
revving higher at any speed than normal, and also your speed will be overreading - telling you that you are going faster than you really are.
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OvalGlen
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| posted on March 11th, 2003 at 07:46 PM |
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What sort of wheels are you running?
is the reason for not up-sizing wheels , they are expensive ?.
I run 15 inch rims with 205 75series (80 series if I could get them ) and this gives an impressive rear wheel diameter.
I run the 1500 VW gearbox and gives in the order of 2000 rpm per 40 mph.
Down side is 50 and 60 km/h is usually 3rd.
I used standard VW centres with commodore rims.
I had the rim offset so that the wheel outside is just a fraction wider than standard.
I have noticed in the past that increasing rear wheel track tends to over stress rear wheel bearings and leads to premature replacement.
Regards,Glenn>
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LittleRalph
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| posted on March 11th, 2003 at 08:57 PM |
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Sounds like I stick with the same box and "get a good stereo".
I just measured the wheels and they are 24" diameter. They came with the car and are nice "wire spoke" look alloys that match the
colour of the car. They stay. (Brand new tyres as well)
If the revs are OK for the engine at that speed then I'll leave all alone. Sounds like way to much trouble for some minor gains at top end and
then potential probs at other speeds.
Thanks.
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type82e
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| posted on March 12th, 2003 at 09:34 PM |
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the biggest tires you could fit on your 14" rims is 205/75/14 or 195R14 which would be about a 27" tire which is a significant reduction in
revs.
a normal vw tire is 26" so it has smaller than normal tires on it at the moment.
marcel
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56astro
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| posted on March 13th, 2003 at 01:38 PM |
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As a side-line comment, before I had my L-bug box rebuilt with a 0.82 4th gear, I was looking at the 3.44 ring & pinion from Custom Speed Parts.
Would have made all gears taller, just what I was after.
Then I saw the price. OUCH!
I think my early beetle manual tells me that tyre height is 25".
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68AutoBug
A.k.a.: Lee Noonan
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 posted on March 13th, 2003 at 04:28 PM |
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Change Your Wheels NOT your gearbox
[size=4]Changing gearboxes is a bit of a Hassle IMHO, but actually pulling a gearbox apart... You need to know what You are doing.... like a mechanic
!! "As VW used to say in their adds in the single port engine days - The Maximum Speed is Cruising speed " I don't believe I ever
read or heard that after the twin Port Engines arrived on the Scene!! Anyway, I'm going out to measure My chromed wide wheels with 14"
tyres and My 165 x 15" tyres on standard VW Rims. Standard Beetle tyres used to be 155 x 15" when Radial tryes became common... Now I
mostly see 165 x 15" tyres. they used to be on type 3 rims which are slightly wider..than beetle rims.. Changing Rims {wheels} is much easier
than gearboxes... and then there are ALL the different size & profile of tyres to consider these days.. [/size] :bounce:bounce:bounce:bounce
- [size=4]Helping keep Air Cooled VWs on the road - location: SCONE in the Upper Hunter Valley - Northern NSW 320 kms NNW of SYDNEY--- [/size]
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70AutoStik
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| posted on March 13th, 2003 at 08:34 PM |
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Have to agree there, if you don't have the equipment and know-how, your box will be noisy and rather short-lived when you get it back together...
The Ring&Pinions are fairly interchangeable between models of gearbox (but there are two different types of pinion,) and if you can find a
VW-savvy tranny place it would be the easiest to change. However, Berg made a good point about lowering the final drive ratio in an air-cooled
vehicle - it will take the same amount of power to maintain a particular speed, but the fan will be turning slower, providing less cooling. Many have
made such changes and are happy with the result (usually with larger engines to make up for the torque lost with the lower ratio,) however, but you
should consider that VWs were known for being an economical car in their day and I suspect the VW engineers chose the lowest ratio they could get away
with (e.g. Autos and 1300s had the higher ratio.)
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LittleRalph
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| posted on March 13th, 2003 at 10:12 PM |
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I'm well convinced. The gbox stays as is.
I'll investigate the larger tyre sizes etc. As I said before, the ones that came with the car were brand spanking new. They also seem to handle
well and have been good in all the wet we've had so I'll stick with them if I can.
I don't really have much time to play with things at present even if they did need changing so I'll keep running it as is and "see how
she feels" over the next few weeks. Then if I do need to do something I'll have all these options to consider.
Thanks again.
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