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Discussion Starter #1 (Edited)
Hey folks,

I'm looking over some plans for Frankenrover 3.0. Looking to make it lower, wider, lighter, more purpose built crawler.

First up - gear ratio's

300 Tdi (tweaked) - R380 - 1.4 LT230 - 39" tires (also Ashcroft underdrive for the crawly stuff)

Need a good axle ratio for decent on road performance (ie able to drive 65-70 on the highway).

Thoughts on axle ratio? Some axles I have access too have 4.56's but I think I'll be lugging it a bit from a stop in first gear with those.

PS - at some point in the future I will have the Mogs currently in Frankenrover for sale (Narrowed 404's and front diff flipped to passenger by Exaxt) - high steer arms - full hydro front - 5 walker evans beadlocks in mog pattern (one new). Hit me up if you have some interest.
 

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I have no experience with similar setups, but I think you're going to struggle with the limited power and RPM range of the 300 TDI and 39" tires.

Obviously you can do the math to figure out your RPM's at 70 mph with different gears, but that won't tell you how acceleration in 1st gear is going to be.

I'm basing this off most people saying that 300 tdi's struggle at highway speeds even with 33 inch tires. All of my vehicles with large tires that still had balls of the line were geared down enough that they turned close to 3,000 rpm at 70, except for my 7.3L diesel which was a torque monster.
 

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Discussion Starter #3
Mostly want a usable 1st gear in high range and low range. If the top speed is >60 I'm good.
 

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I am running 5.38 and 38" tires with a 1:1 t-case and 3.06 1st gear auto trans.
It goes pretty good off the line, but it is rev happy at 65mph.
 

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Those last two posts, are those results with a 300Tdi engine?

As per the second post, the low power from a 300Tdi (I had one with turbo and injection pump upgrade for many years) is an issue with speed from a vehicle with a large frontal area and poor aerodynamics.
 

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yes stock 300tdi r380 1.2 lt230. 4.37 axle ratio with 36 inch tires. has the same rover get up and go as my stock disco v8. i know thats not saying much but its a good way to visualize it.
 

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I'd get Jesse Haines to build me a set of portals...MUCH lighter than the Mogs but you get the benefit you have been enjoying...value for money is there too in regards to gearing...

I think whatever diff ratio you choose, your issue will remain your first gear will be an issue...maybe Dave from Ashcroft can build a specific "lower" 1st for the R380 (I'd buy one)...let's say a nice 4-5 to 1 ratio...then you can get the high speed from the diffs (higher gearing and under drive for crawling), but at least you have the "up and go" from this new 1st gear...

Jesse H has been able to move the lower shock mounts to a VERY low point on the H1 portal boxes he builds, therefore creating a lower stance overall with the travel you would need...also, he uses either a Toyota 8" or a Ford 9" 3rd member...the latter has a boat-load of ratio options for you to choose from. You can push the diff to one side completely in order to clear any chassis/drivetrain items and further build low...

8 lug outers can give you loads of wheel options too (off the shelf) and therefore you can build the axles with a wider WMS and therefore have less offset wheels to get good steering geometry and less stress on your steering components...

Finally, and you probably know all this previous stuff and that a 3 link would help keep things lower than clearing a 4 link (especially up front)...

Always loved FR1.0, 2.0 and now looking forward to 3.0!
 

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Discussion Starter #11
I'm going as low as possible with the build so portals are out of the equation. Might even notch the front frame for a bit more clearance. The rear frame will be completely gone and replaced with tube. I'm looking for extreme off camber stability (I have always hated severe off camber stuff). The breakover will be low - but the drivetrain is completely covered by the frame and a smooth flat belly pan will help.

I was up in Moab a few weeks ago discussing the build with Jeff at Dirt Squirrel Fab. He and I have some interesting plans for the build. Sort of an old school tray back Defender meets new school buggy/truggy with some old SG buggy themed styling (always loved that rig - Greg always had the aesthetics perfectly dialed in).

I think I should be good on gearing overall, with the Ashcroft underdrive to play with.

Frankenrover 3.5 might have a new engine choice or engine mods, but 3.0 will stick with the Tdi.

More to come. Thanks for the input folks.
 

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Good stuff! Agree on the SG aesthetics...I just test-drove my truggy this past weekend...at 102" outside of tire width, and relatively LOW height despite the 54s, I hear you on the off camber stuff...

I too went all tube both in front of the cab and behind...check all the ready to install kits from the UK for the challenge trucks...can help with some inspiration what to do (or not to do).

Nadim
 

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Discussion Starter #16 (Edited)
Some updates :)
 

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