Taller 4th gear?

[SL12572]

I'm looking at possibly changing my 4th gear to .77

I've heard mixed opinions about doing this. I'm primarily looking to get the engine rpms down a bit and slightly increase MPG. This will be initially on a stock syncro with a 2.1, but eventually on my turbo 2.1. Right now I'm running BFG AT 15" tires, but will be changing over to the biggest tire I can get to fit.

I've heard bad stories of changing to a taller 4th, which ended up useless, unless downhill or completely flat ground. Was this while using a .77?

Anyone with a taller 4th and a stock 2.1?


Thanks!

[16CVs]

I had GW do my Syncro trans . Actually I bought a rebuilt from them and gave them my core.
Part of their standard rebuild is a taller 4th gear . I have a 2.2 with a decoupler and 16 " wheels ,which have the same overall height of my 14's .
Since my gas gauge is in op ,I live off of my Mileage counter . My first tank after my trans change was 291 miles ,up from about 241 . now 10K miles later it is still somewhat consistent depending on how I drive ,but it hasn't been less than 260 per for sure .
Although it should be noted that my speedo runs about 10% high . So the mileage numbers may skew but the percentages are real.
I see no down side to a taller gear ,I drive a lot .generally about a tank every 3 days , I can use anything I can get .
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[Jake de Villiers]

[Jeff's Old Volks Home]

My Advice is at least to match the 3rd gear equally as tall or you'll have a huge hole between 3rd and 4th. So between 80 and 110kph what ever gear you're in, you'll be in the wrong gear. You'll be screaming in 3rd just to shift into 4th and not be in the sweet spot. I went back to stock gearing with my mildly tuned AAZ Syncro doka, with 215/70/16 General Grabber AT2 and she's just a hair above 3000rpm at 100kph. I'm happy with the combo.
Jeff

[morymob]

My '86 syncro has 88 final and i don't like at all, drops too easily on a hill, has new motor also and stock dia tires. If u can get/borrow 2 rear tires -27"-28" tall,drive and u will see about what u will end up with. My stock '88Westy will run off and leave it in hilly areas.

[dobryan]

I have a 0.77 fourth gear and about 10% larger than stock tires (third gear is also taller). But I am running a Subie 2.5. I like the combination.... but I have not driven in the Rockies yet....

70 MPH at 3400 rpm, and I can easily cruise in third at 60 mph up hills if I had too. So far no need to downshift going up grades in fourth East of the Mississippi.

Of course this gear/tire combo would be a dog with a stock engine.
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'87 Westy w/ 2002 Subaru EJ25 and Peloquin TBD

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[getset]

I too am contemplating this question. I recently bought a Syncro that needs an immediate transmission rebuild. My initial plan was to hold off until I did an Engine swap, but since it seems like an immediate problem, do I change gearing or not? At this time I am leaning to not changing the gearing. I had a syncro with a subie conversion and 215 75 r 15 tires on it. It seemed to be just about right in power to gearing ratio. I however am planning on a little more power this go around so I am torn. The power is less about speed, so I am inclined to keep the stock transmission gearing. Looking forward to hearing more opinions.
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87 Syncro sunroof w/ 2.5 Subaru.
2015 VW golf TDI

Bikes, KTM motorcycles, sailboats, and busted knuckles.

[crazyvwvanman]

Keep the stock gearing. Make any desired tire/wheel changes first. Do the engine swap and see how it drives with stock gearing for a while. If not to your liking THEN think about changing the gearing to what you hope will be better. After you do this you will actually have learned what effects just the gearing changes had. Doing a gearing change at the same time as an engine swap denies you the chance to learn the most about what you are doing. You might be shocked to learn how many Syncro guys made big gearing changes along with engine conversions only to pay again to undo some of the gearing changes. Others just live with their regrets until the tranny needs work again. The most common regret is TOO TALL of 4th and the next is TOO BIG OF A GAP between 3rd and 4th.

None of the gasoline to gasoline 4 cyl swaps require gearing changes. Yes, you can improve some aspects for better results under certain conditions but these involve tradeoffs too.


Mark

[joseph928]

Have a .77 fourth and 215-75-15 BFG AT -love it but I have a GW 2.3 that helps and I like rock crawling to much so have 6.17 RP so mountains are no problem! And yes I can't go 75, HA! 60-65 OK I came from an 1982 diesel , ha! I'm fast now! PS did 3rd gear to.
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[bluebus86]

I think the bottom line is these vans NEED a fifth gear for highway driving if you want to cruise at 70 mph.

[odin43]

i have a .77 in my syncro. im running a 2.3 audi thats been warmed up a bit and is running on eurovan digifant 2. i would guess its making in the 140-150 range for both hp and torque. i am running 16's with 215/75/16. that 4th gear sucks. dont do it unless you change 3rd and have plenty of power to pull it. the gap between 4th and 3rd is gigantic, which means you are constantly screaming or lugging on lots of the terrain in our neck of the woods. the upside is that it is great on the flats, downside is that it is useless on hills. luckily for me the audi 5 likes to spin and will run at 5500 rpm all day. pm me if you want to drive my van before you commit.
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86 syncro
02 passat w8

[BillM]

I did had a .77 installed in my old 91 hardtop. It made
driving on a road where the traffic was between 30-40mph
miserable. 3rd was low and 4th to high. I found myself
shifting back and forth way more than I wanted to. Even
a motor change from the stock 2.1 to a HO tiico it was
still to large of a gap from 3-4. I ended up regearing
3rd to help a bit as the inline liked higher rpms and
didn't mind taching second gear out. In the terrain I
drive second gear was used for a shorter time much like
first gear versus I tended to cruise more in third and fourth
depending on the speed limit/traffic.
I think the best option out there is the Subaru transmission
project. I think that would be a perfect match for my Zetec
Turbo. I like to drive 80 on the highway and would love
to knock the rpms down a bit with a fifth gear.
_________________
Bill M
87 Westy

[SL12572]

Thank you for all of the good advice. I think for now I'll keep the stock gearing, but put on some taller tires. Last thing I want to do is tear apart the transmission, to end up with a gear I can't use. A 4 speed is bad enough. I don't want to make it a 3 speed!

When David Clymer finishes the subaru transmission for the Syncro, I will be a happy camper.


Scott

[J Charlton]

If you look at http://www.t3-infos.de/images/T3-Getriebe.pdf and scroll to the 5 speeds, you'll see the number and variety of 5 speed gearboxes that VW put in vanagons worldwide - except N. America.
The 5th gear isn't geared much higher, if any, than the 4th in a 4 speed, but the existence of 2 gears between 2nd and final means that there are options to avoid engine screaming and/or lugging.
In fact, VW couldn't sell 4 speed gassers succesfully in Europe - 5 speed diesel TDs were the powertrains of choice - guess that's why we got the 4 speed gassers.
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