A Rubicon build story

[Maverick23]

Some WAR PAI NT

[Maverick23]

That should have said "WAR PAINT" 

 

The sun came out … maybe this is a better picture?

 

 

 

Edited February 11, 2019 by Maverick23

[Chrisby]

And there was all of us thinking you might have got it muddy !

[Maverick23]

A NEW FACE !!

 

 

 

Rigid Industries TRUCKLITES courtesy of BUZZ (thanks Alex )

"Classic" Angry Grill from eBay (UK Supplier) and painted locally

New black "Jeep" badge as a finishing touch

 

 

[Maverick23]

STAGE 5 (possibly) – 3.5” LIFT KIT

 

This update is long overdue.

 

The Jeep paid a visit to Alex (BUZZ Special Vehicles) late last year and he installed a JKS 3.5” JSPEC lift kit – including Fox 2.0 ATS (steering damper); Fox dampers with reservoirs; correction brackets; front & rear adjustable track bars; Plus Yukon Drive shaft (front YDS022) – to cope with extra angles involved. Not required to change the rear drive shaft … but I am tempted to upgrade that at some point 

 

A couple of gremlins:

1.     My fault. I ordered adjustable lower control arms, as I thought the caster might need adjusting. However, they were slightly longer and only adjusted to get even longer … so they crushed the rear springs!! Naivety on my part … would be useful if fitting a full long arm kit. DOH! And NO!

2.     The new adjustable track bar fouled on my AEV diff cover … which was a big surprise to me and Alex. Luckily the existing Teraflex track bar was still in good condition, so went back on … all good.

 

Thanks as always to Alex & his team. Not many pictures …

 

 

 

[Maverick23]

37” TYRES (at last)

 

BFG KM3 37/12.5/R17

 

Pic 1
 

Will they fit !?!

Pic 2 &3

I guess they did …

 

Pic 4, 5 & 6

 

Now fully settled … out in the sunshine ... clean AND the right way up !!

 

 

It has been a few years in the making … but really pleased with the final result. I chose the lift kit and drive shaft a long time ago, then waited and waited for BFG to bring out 37” KO2’s to the UK. Last year they actually made it onto the UK website … then in early this year they disappeared again. BFG finally confirmed they were a “no go”.

So frustrated and annoyed. Alex said “just get the KM3’s … you won’t notice the difference”. My own KO2’s were showing their age a bit (6 years old) … so I bit the bullet and got mud terrains. And ofcourse, Alex was right. Such an amazing advance by BFG to produce a
n MT tyre that is quiet and civilised on the road. Happy Jeeper 

 

PS no idea what happened to the pics ... they were all the right way up in my album ... now all over the place 

 

[TimC]

37s at last eh Kerry! Looking really good . Just the V8 conversion to go now

[Maverick23]

2 hours ago, TimC said:

37s at last eh Kerry! Looking really good . Just the V8 conversion to go now

Thanks Tim 

 

Yep, just the V8 and it’s all done

[frosty]

what axle ratio's do you have , i put 4.88's in mine, i am on 35's, toying with 37's as the ratio's can handle it. 

[Maverick23]

3 hours ago, frosty said:

what axle ratio's do you have , i put 4.88's in mine, i am on 35's, toying with 37's as the ratio's can handle it. 

Hi Frosty

 

Following advice from Alex … I am still on the original Rubicon 4.10.

 

While I was on metric 35” tyres, I really didn’t notice much difference. Now on imperial 37” … the tyres have changed the gearing. However, it is actually running less rpm at cruising speeds - was 2,500 for 70mph, now 2,300 - which I quite like. I tend not to drive it as a race car, so if it has lost a bit of initial acceleration, I really haven’t noticed. MPG maybe from 20 down to 19.5.
 

NB real tyre size is now 35.5” (was 33.5” before) … that needs to be taken into account. My own thought would be to maybe move to 4.56 … but not 4.88 after my experience. ALSO my existing gearing would probably suit the installation of  a more powerful engine - V8 anyone

 

All the best for whatever you decide to do … bigger tyres appear to be the only way to raise the fixed axles … and they look great

[V]

I have been running 4.56 with 33" tyres for 21 years with the same 29 year old original automatic transmission in one XJ and 4.88 with 35" tyres for 16 years with the same 21 year old original automatic transmission in the other. I don't have 4:1 transfer cases, so I like that the lower final drive also improves my low ratio gearing off road. I also have engine braking under manual shift control for hill descents. Both Jeeps have better acceleration than they were stock even with all of the mods.

 

The final drive ratio is largely down to the preference of the driver but there is a simple test that will determine if you are putting the transmission, manual or automatic under strain. For a manual in high ratio it should be able to pull 5th in a 5-speed box and 6th in a 6-speed box at around 50-60mph and sustain it to 70mph. If it can't, then your gearing is too high for the vehicle's weight and power. On an automatic, it's a bit harder to detect, but the torque converter should be able to lock-up at every realistic opportunity to do so. If not, the transmission will run hotter because it is slipping the torque converter excessively. If adequately cooled the transmission fluid will avoid being burnt, otherwise the heat from continual slippage can lead to accelerated internal wear of the transmission. I guess that on flat level motorway if the auto transmission cannot sustain cruise control at 50, 60 or 70mph without shifting down, that might be a reasonable indicator. I have only run 33" tyres on 3.55 gears for a few weeks and I remember that cruise was almost unusable while I was waiting for my gears to arrive.

 

Jeeps sold in the USA are often equipped with the weirdest stock final drive ratios compared to European models. There are many more Jeeps on the road globally running high ratios with big tyres than the ratios I would choose for my Jeep. If it works for you, and you are happy with how your Jeep drives, that's all that matters.

 

[Maverick23]

Thanks for your knowledgeable input V. 
 

I have seen the theoretical gearing tables … for my 35.5” tyres I should probably be on 4.88. But even in discussions with Yukon, they thought 4.56 would be fine with my 3.6L Rubicon. There are stories in USA of re-gears being reversed after fitting more powerful engines … like the unicorn V8. 
 

My Jeep seems to run just fine and cruises along happily even above the legal limit … briefly while overtaking ofcourse

[V]

1 hour ago, Maverick23 said:

There are stories in USA of re-gears being reversed after fitting more powerful engines … like the unicorn V8

That's understandable. If your engine has enough power to pull a higher final drive ratio your Jeep will benefit from having more teeth on the pinion gears making them less likely to fail. I think 4.88 has one less tooth than 4.56, it doesn't sound much but the pinion gear gets bigger for each extra tooth. If you take a look at a 5.38 pinion you could easily mistake it for a drill bit, they are tiny.

[frosty]

On 20/07/2022 at 02:41, V said:

I have been running 4.56 with 33" tyres for 21 years with the same 29 year old original automatic transmission in one XJ and 4.88 with 35" tyres for 16 years with the same 21 year old original automatic transmission in the other. I don't have 4:1 transfer cases, so I like that the lower final drive also improves my low ratio gearing off road. I also have engine braking under manual shift control for hill descents. Both Jeeps have better acceleration than they were stock even with all of the mods.

 

The final drive ratio is largely down to the preference of the driver but there is a simple test that will determine if you are putting the transmission, manual or automatic under strain. For a manual in high ratio it should be able to pull 5th in a 5-speed box and 6th in a 6-speed box at around 50-60mph and sustain it to 70mph. If it can't, then your gearing is too high for the vehicle's weight and power. On an automatic, it's a bit harder to detect, but the torque converter should be able to lock-up at every realistic opportunity to do so. If not, the transmission will run hotter because it is slipping the torque converter excessively. If adequately cooled the transmission fluid will avoid being burnt, otherwise the heat from continual slippage can lead to accelerated internal wear of the transmission. I guess that on flat level motorway if the auto transmission cannot sustain cruise control at 50, 60 or 70mph without shifting down, that might be a reasonable indicator. I have only run 33" tyres on 3.55 gears for a few weeks and I remember that cruise was almost unusable while I was waiting for my gears to arrive.

 

Jeeps sold in the USA are often equipped with the weirdest stock final drive ratios compared to European models. There are many more Jeeps on the road globally running high ratios with big tyres than the ratios I would choose for my Jeep. If it works for you, and you are happy with how your Jeep drives, that's all that matters.

 

good article Vince, as per usual. i changed my gearing at the same time as having my diff's rebuilt, and the axle cases strengthened ( inside and out), i was having problems with my auto box overheating and destroying the oil, i had added a second gearbox cooler, which did help, but changing the ratio'e solved the root cause of the problem, also as you said, it makes very steep descents more controllable.  as you have said, it depends on what you use your jeep for, mine has always been for extreem off road use, i have other cars, and jeeps for daily use.