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Engine RPM vs Speed. Taller Gearing?

Printed From: The Brick-yard
Category: T3 Section
Forum Name: T3 Tech help
Forum Description: Forum for T3 specific problems.
Printed Date: 30 Oct 20 at 20:17
Software Version: Web Wiz Forums 12.01 -

Topic: Engine RPM vs Speed. Taller Gearing?
Posted By: retroloz
Subject: Engine RPM vs Speed. Taller Gearing?
Date Posted: 14 Oct 19 at 17:23
Hi all, quick bit of info:

1988 T3 with AGG engine conversion (was a KY 1.7 Diesel)

3H gearbox 5 speed

Stage 2 Uprated clutch

Rear tyre size is 245/45/18 4% over stock tyre size

At 60mph Im just a tad over 3000rpm

All is going well with the engine but Im just trying to get some ideas together to see whats possible.

My mpg is shocking really, I can almost see the fuel go down after a couple of trips to town, town being 7 miles away. I reckon its in the low 20s if 20 at all.

Been trying to find info about either swapping the final drive or changing out the 5th gear to help with the economy.

4th and 5th are so close with only a little drop in RPM when I change from 4th to 5th and I can even blip up some shallow hills without changing down.

I recently visited the Aidan Talbot website but the front page says he has been away since Monday 16th April 2018.

Also on the brick-yard website the 5th gear seems to be a common size, so I dont want to replace that with the same or even lower one.

Ive checked my gearbox code on the Rjes site and its at the top in light green and is quite accurate to my reading, but my tacho guage might not be that accurate so my rpm spec is just and estimate really.

Anyway its a long shot seeing if anyone has had a similar issue and or even swapped out gear sets or final drives.

Or is this as good as Im going to get and should I just pay the fuel bill. I want to make the van a motorway cruiser as Ive got plenty of power with my 8v AGG unit which I love.

Also I dont want to go the flipped passat route, I want to keep it as simple and standard as possible.

I know its alot to take in and I'm not expecting miracles anyway thanks for having a read.

1983 mk1 Golf
1988 VW T3 GTI
2002 VW Golf MK4" rel="nofollow -

Posted By: ob1
Date Posted: 19 Oct 19 at 10:13
cheapest option is just fit the tallest rear tires you can squeeze in..  I had 215 75 16 in under my arches which helped bring 70mph to around 3.2k rpm ish...     else it's at least 1.5k on a gearbox rebuild and that's a fair amount of fuel! 

Posted By: retroloz
Date Posted: 22 Oct 19 at 13:11
Yea, I know its been covered alot over the years, just seeing what people are doing recenlty.

I am looking to drop back down to 16inch wheels for a bit of comfort and tyre choice and price.

Looks like I will forget about the gearbox for now then.

Also I am not currently carrying a spare wheel so wanted to get a whole set of steel wheels.

Didnt quite want to end up like this>>> but it looks cool

1983 mk1 Golf
1988 VW T3 GTI
2002 VW Golf MK4" rel="nofollow -

Posted By: retroloz
Date Posted: 23 Oct 19 at 10:55
^^^^^^^^ not my syncro by the way ^^^^^^^^^^

1983 mk1 Golf
1988 VW T3 GTI
2002 VW Golf MK4" rel="nofollow -

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