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Engine Specific Info and Questions => IDI Engine => Topic started by: jlpst94 on July 24, 2013, 03:34:00 pm

Title: Tallest 5th gear possible
Post by: jlpst94 on July 24, 2013, 03:34:00 pm
I'm currently running an EcoDiesel tranny with an AVX code.  I looked it up and it's got a .75 5th gear ratio which is one of the taller 020 5th gears.   It's still revving too high on the highways for me.  Is it possible to swap in a newer TDI tranny or any other tranny?  Anyone have any options for this.  I'd love to be at 2500rpm cruising at 65-70.   
Title: Re: Tallest 5th gear possible
Post by: jlpst94 on July 24, 2013, 03:50:59 pm
I guess I shouldn't just ask for the tallest 5th gear because of the different final drives.  What are my options to get lower rpms on the highway?  The EcoDiesel tranny runs around 3500 at 70mph and I'd love to get it lower
Title: Re: Tallest 5th gear possible
Post by: 8v-of-fury on July 24, 2013, 06:14:08 pm
Pretty much al the other .75 and .71 transmissions (020) cruise 100 (60mph) at 2500-ish.

The AVX has a 4.25 F/D and it shows. Be a good trans for a screamer 16v lol!
Title: Re: Tallest 5th gear possible
Post by: theman53 on July 24, 2013, 07:34:33 pm
http://www.scirocco.org/gears/
Title: Re: Tallest 5th gear possible
Post by: CrazyAndy on July 24, 2013, 07:49:34 pm
Just get an FF out of a cabriolet and be done with it.
Title: Re: Tallest 5th gear possible
Post by: EcoTX on July 24, 2013, 11:29:32 pm
Lots of time, effort, and money for a few hundred measly RPM I say, just live with it.

The last tank in my ECOdiesel was 645.3 miles on 14.213 gallons.
That's 85% highway / 15% city.
Still managing mid 40's running 70-75MPH up there around 3500 RPM after all those years and miles.

Car just rolled over 392,000 miles, original engine, original headgasket, original turbo, etc.
I did burn up 5th gear in the original AVX tranny awhile back, but promptly replaced it with another AVX because it is a great transmission and great match for the 1.6TD with the K14.
Those Germans matched that tranny to that engine for a reason...and if you've never driven the combo you can't really say much.
Title: Re: Tallest 5th gear possible
Post by: 8v-of-fury on July 25, 2013, 04:43:21 am
This is true sir..

Our 1.6TD and 4S trans loves to be above 3000RPM on the highway.. and we squeeze nearly 50 out of it every tank.
Title: Re: Tallest 5th gear possible
Post by: Gizmoman on July 25, 2013, 05:43:43 am
Possibly install some sound deadening or turn the volume up on the pod?
Title: Re: Tallest 5th gear possible
Post by: jlpst94 on July 25, 2013, 10:30:53 am
I guess it is a lot of work but I'd like to get a tranny ready for my next build or if this car fails.  Maybe the cabrio tranny is the one to get.  Thanks guys 
I do get around 50mpg so I shouldn't complain.  Maybe a louder stereo is the fix
Title: Re: Tallest 5th gear possible
Post by: bbob203 on July 25, 2013, 10:39:27 am
I installed a modified passat b3/b4 inner boot on my mk2 and it killed a lot of sound. its a heavy rubber boot that goes under the outer cosmetic boot.
Title: Re: Tallest 5th gear possible
Post by: libbydiesel on July 25, 2013, 03:22:51 pm
An 020 swap is an easy afternoon...
Title: Re: Tallest 5th gear possible
Post by: 8v-of-fury on July 25, 2013, 03:35:17 pm
An 020 swap is an easy afternoon...

'ay, but for a few hundred RPM?
Title: Re: Tallest 5th gear possible
Post by: 745 turbogreasel on July 25, 2013, 05:44:27 pm
Yep
Title: Re: Tallest 5th gear possible
Post by: libbydiesel on July 25, 2013, 09:11:42 pm
Absolutely.  If I had an AVX in an ECO I would most certainly swap it out along with the injection pump and the soda straw exhaust...
Title: Re: Tallest 5th gear possible
Post by: mzak88 on July 25, 2013, 10:06:51 pm
I swapped a tdi o2a ctn into my 3. Changed fifth gear from .74:1 out for a 0.658:1 set. Combined with my ctn's 3.164:1 R&P, 110km/h (70ish), is achieved at 2100.
Title: Re: Tallest 5th gear possible
Post by: bbob203 on July 26, 2013, 05:22:38 pm
Absolutely.  If I had an AVX in an ECO I would most certainly swap it out along with the injection pump and the soda straw exhaust...

The eco exhaust is at least bigger than an na exhaust.
Title: Re: Tallest 5th gear possible
Post by: Jetmugg on July 26, 2013, 09:10:28 pm
Get taller tires.
Title: Re: Tallest 5th gear possible
Post by: Gizmoman on July 26, 2013, 10:08:27 pm
That's what I did on the van - works good but it raises all of 'em.
I have a K14 and getting the breadbox rolling up a hill from a dead stop is trickey.

I'm speaking from memory though - I'ts been in rebuild mode for over a year ;D
Title: Re: Tallest 5th gear possible
Post by: 92EcoDiesel Jetta on July 27, 2013, 10:08:32 am
Get taller tires.


Is the results the same as changing final drive at same rpm?
Title: Re: Tallest 5th gear possible
Post by: 8v-of-fury on July 27, 2013, 10:25:47 am
175/70/13 with 3.94 and .71 is 2500 @ 60 - with 3.67 and .71 is 2300

185/70/14 with 3.94 and .71 is 2300 @ 60 - with 3.67 and .71 is 2100

Title: Re: Tallest 5th gear possible
Post by: 92EcoDiesel Jetta on July 27, 2013, 11:09:03 am
Aerodynamics aside from bigger tires provided there is no interference in wheel wells, seems much easier than changing the diff to lower rpm.
Title: Re: Tallest 5th gear possible
Post by: libbydiesel on July 27, 2013, 11:36:50 am
There are more significant downsides to larger tires than aerodynamics, most notably the added rotating mass hurts fuel economy during acceleration (similar to added weight in the car) and makes the brakes less effective (similar to added weight in the car).  It's a better idea to get close with gearing and fine-tune with small changes in wheel/tire size.  When you consider the cost of used larger rims and new tires the cost is more than a good used trans.  Swapping a trans is a little more work than swapping 4 tires.  The trans you pull out can usually be sold for close to or the same as what you pay for the taller geared one - there are certainly folks who want the close ratios for added pep.  Used 13" rims and tires are hard to give away and go bad on the shelf.   
Title: Re: Tallest 5th gear possible
Post by: 92EcoDiesel Jetta on July 27, 2013, 02:42:36 pm
If rotating mass is an issue why are new cars going with bigger and bigger wheels? Why not go the other way?
Title: Re: Tallest 5th gear possible
Post by: libbydiesel on July 27, 2013, 03:24:40 pm
The short answer is that cars have gotten heavier to accommodate stricter safety requirements and given two sizes of the same model of tire with the same aspect ratio, the larger size will carry a higher load rating.  Heavier cars = bigger tires.  Newer cars also have much larger brakes to accommodate stopping both the heavier car and the bigger tires...
Title: Re: Tallest 5th gear possible
Post by: CrazyAndy on July 27, 2013, 06:43:33 pm
The short answer is that cars have gotten heavier to accommodate stricter safety requirements and given two sizes of the same model of tire with the same aspect ratio, the larger size will carry a higher load rating.  Heavier cars = bigger tires.  Newer cars also have much larger brakes to accommodate stopping both the heavier car and the bigger tires...

Also the trans final drive is selected with both engine power, vehicle weight and wheels' tire size taken into accommodation.  That's why the 2013 passat TDI rides at 70mph @ 2250 on a relatively flat beltway-style freeway and has good power.
Title: Re: Tallest 5th gear possible
Post by: 8v-of-fury on July 27, 2013, 07:50:57 pm
If rotating mass is an issue why are new cars going with bigger and bigger wheels? Why not go the other way?

Those bigger alloy wheels are probably still not that much heavier than our thick gauge steel rims.

I didn't notice any hit in mileage or performance when going from the 175/70/13 to the 185/65/14's on the mk2.