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VB 308 T5 - diff ratios?

TrickVB

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Building a VB with a mild (around 320hp) with a V8 T5. Have a disk 10 bolt but has 2.60 gears (out of car in do nic). tyres are 245/45/17. How bad will it be with a 2.60. Its a cruiser on the highway, not a traffic light dragger. I know I can change to 2.78 but if I want 3.08 or higher I have to change the carrier etc. Will it labour with such a set up (a dog to drive) and should I cut my loses and do something elese with the diff?
 

immortality

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Try it and see as that will cost you the least and then spend money if you don't like it. I don't think it'll be great but if it's just a cruiser it may not matter.
 

gtrboyy

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Change it....even 3.08 gears will suck at low revs if it has a decent cam.

3.36(?) or 3.55 will be fine that way can actually use 5th gear.

Better yet look up revs it will be doing with online calculator where you punch in diff ratio,tyre sizes with gear ratio & work out what will work with your setup.
 

MuckUte

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I would say give it a go. Depending on which T5 you use they have different ratios.

I had a T5 in a WB ute with a stock 304 with 3.08 diff and 1st didn't get used much.
 

Vin999

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Building a VB with a mild (around 320hp) with a V8 T5. Have a disk 10 bolt but has 2.60 gears (out of car in do nic). tyres are 245/45/17. How bad will it be with a 2.60. Its a cruiser on the highway, not a traffic light dragger. I know I can change to 2.78 but if I want 3.08 or higher I have to change the carrier etc. Will it labour with such a set up (a dog to drive) and should I cut my loses and do something elese with the diff?
Some good points posted already, especially the "change it".

A 2.60 snail, 2.78 turtle, 3.08 would be more suited all round considering 4spd plus o/d box, especially as highway cruiser with 5th for fuel economy. Most diff ratio’s are chosen basically on 1st n last gear you’re running in car g/box apart from other drivetrain/engine sheet. Lower ratio diffs use /have higher 1st gear ratio boxes and no o/d.

I had before conversion 6cyl, 8bolt 2.78 with 3spd traumatic auto, also used for standard 253 engine.
Now running 304 with 700 4spd auto and I have VK Salisbury 10bolt 3.55 LSD and its brilliant in city traffic without o/drive and great with pick up as highway cruiser with overdrive.
Uses slightly more fuel due to higher revs/ratio but still economical and factory feel if you don’t plant the old lead foot.
I originally wanted to use 3.36 slight improvement in pickup and acceleration all round to a common 3.08 BUT couldn't find one, I was lucky to find the rarer 3.55 10bolt lsd and happier I did in the end apart from knowing, eventually to many spins and the lsd spider gears will croak.

Since your building engine, Look for a standard VB/VK 3.08/3.36/3.55 10bolt LSD Salsbury as your best option depending on what you find.
If you decide to change to the VK on B/W 28 spline diff is worth the spend for a V8. B/W 25 spline is a bit weak for V8 even if you drive like a grandpa.
 

Lacksballs

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The taller diff ratios were all about reducing the RPMs at cruise (maximising fuel economy), so with a T5 you can be a lot more aggressive with your final drive selection as you have an over drive top gear to minimise RPM @ say 100kph. Go 3.55 or 3.73 and you can have the best of both worlds, great accelaretion & good cruise (fuel ecomony).

If you think about a M21 4 speed with a STD V8 3.08:1 RAR on say a 205/70/15 tyre in top gear @ 100kph it will be 2500rpm, with 3.55:1 with a T5 in 5th (0.73:1) @ 2000rpm it will be 100kph. (APPROXIMATELY).

There are plenty of online calculators you can use:

Here is how mine worked out, I went for the std 3.23:1 RAR from the 6 cylinder donor vehicle.

Screen Shot 2017-03-10 at 10.18.55 am.png
 
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