Underdrive unit?

[TeriAnn]

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What has your experience been with your high ratio transfer case?
In 1st gear my truck is moving along at about 10 MPH.

I'm the wrong person to ask.

Engine = Ford 5.0L with EFI
gearbox = NP435 (first gear = 4.9:1, yours about 3.6:1)
Transfercase = Series high ratio
Diffs = 4.75:1

The engine has more torque coming off idle than the stock 2.25L does at peak and my first gear ratio is a lot lower then the LR gearboxes.

On the other hand with 33.3 inch dia tyres the engine turns under 2600 RPM at 65 MPH

My guess is your best bet for driving happiness is a stock Series transfercase and a Roverdrive.

[ArlowCT]

My guess is your best bet for driving happiness is a stock Series transfercase and a Roverdrive.

I have driven trucks with the high ratio box and trucks with and without over drives and I would agree with Teriann. Stock case with the roverdrive is the perfect setup for a stock to almost stock engine. I like splitting gears and being in the "perfect" gear at all times. This I felt was impossible with the high ratio box. Plus it's just cool driving a truck with 30 different gear combinations!

[TeriAnn]

I have driven trucks with the high ratio box and trucks with and without over drives and I would agree with Teriann. Stock case with the roverdrive is the perfect setup for a stock to almost stock engine. I like splitting gears and being in the "perfect" gear at all times. This I felt was impossible with the high ratio box.

I have come to believe that Ashcroft offers that box for people with serious engine swap upgrades and not for the 2.25L or 2.5L petrol folks. There are lots of Rover V8 swaps into Series rigs in the UK, making the high ratio box the perfect accessory. The high ratio box is also popular with North Americans doing engine swaps. Advance Adapters offers a family of adapters to go between popular US top loader gearboxes and the Series transfercase (Call and ask for Matt). These adapters make it easy to build an American V8 to American top loader gearbox to high ratio Series transfercase combination.

Unless you get an old Santana or new Heystee Automotive overdrive, an overdrive is just not up to the power of an American V8. Timm Cooper's Monster V8 powered Series I has a Santana overdrive in it. Anything that can stand up to Timm's driving has got to be very strong and reliable.

Back in ancient times when I had a 2.25L engine in my Dormobile and an overdrive, third over was my best friend in the mountains. But with the 5.0 V8 in there, I have yet to drive a paved mountain road where I needed to gear down because the engine was running out of oomph.