Fixing the Diesel (Rubicon) Suspension

[meckanik]

This has probably been addressed a few different ways but I thought I would share my approach. If you have a Diesel Rubicon (other trims are probably similar) you know how soft the front suspension in. IMO it is under sprung and under damped. The front end wallowed and smacked the bumpstops on a regular basis just driving around town as well as porpoising on some concrete road expansion joints. I'm a somewhat aggressive driver and found the performance to be borderline dangerous (even at the slower speeds I was forced to drive at).

I performed a lift/level of the truck suspension at the same time; a lift is probably not necessary to reduce contact with the bumpstops, but as they are lower than the gas engine, it can only help. I moved to 35" tires while addressing the suspension shortcomings so I added a Teraflex 1.5" spacer lift (# 1155300) in the front and a Daystar 0.75" spacer lift (# KJ09192) in the rear.

To address the front suspension issues I used Clayton Jeep Wrangler JK/JL 1.5" & Jeep Gladiator JT 0.5" Lift Front Coil Springs (# COR-1509150) along with Bilstein B8 5100 Shocks (# 33-304847).

For reference after the spacers and springs (stock 33" tires) I netted:
Front Height Increase: 1.75"
Rear Height Increase: 0.5"

According to Clayton, the front coils may net up to 0.5" of lift, YMMV.

I can say the truck should have come like this from the factory; it looks better and drives exceptionally well for a 6K pound truck. There were areas where I would have to slow from 35-43MPH to <10MPH to cross (train tracks for example) that would otherwise slam the truck into the front bumpstops. I've tested all of them at increasing speeds and I'm not hitting the stops any more.

The front end doesn't wallow, and is more planted and stable. It's a pleasure to drive now even with a (synthetic) Badlands Apex 12K winch mounted in the factory steel bumper (Grimmspeed mount).

Edit: I think the rear suspension is probably under-sprung and under-damped as well as the truck still porpoises a bit but feels like the mostly the rear moving.

Pics of the truck (post-lift) on Nitto Trail Grappler MT 35x11.50 tires.

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[NOTJeepBeerSleep]

even my sport diesel was too soft from the factory. mopar 2 inch fixed it for me. really a shame they fucked the dog like they did.

 

[meckanik]

even my sport diesel was too soft from the factory. mopar 2 inch fixed it for me. really a shame they fucked the dog like they did.

For sure, how was it released in that state? Hard to believe any meaningful testing was ever performed during development.

I’ve heard the Mopar 2” lift was a good solution as well, mine was more of a super low cost approach.

 

[NOTJeepBeerSleep]

Yeah I traded a max tow gasser for the diesel. Was really bittersweet until the lift. The jeep rides tits with the lift. I really wanted a lifted truck in the first place so no big deal but if I wanted to keep it stock I would have been way more pissed than I was.

 

[BriGuy]

Appreciate the detailed write up including part numbers!

Did you get the new shocks because they were necessary due to the added ride height from the springs and leveling kit up front or just because they were stiffer/superior in some way?

I just got a 21 JT diesel and it's already got 35s but has the front end rake and I'd like to remove that and eventually when these tires wear out go to 37s.

But also not looking to break the bank to get a little higher and ride better, if I can.

Thanks again.

 

[meckanik]

Appreciate the detailed write up including part numbers!

Did you get the new shocks because they were necessary due to the added ride height from the springs and leveling kit up front or just because they were stiffer/superior in some way?

I just got a 21 JT diesel and it's already got 35s but has the front end rake and I'd like to remove that and eventually when these tires wear out go to 37s.

But also not looking to break the bank to get a little higher and ride better, if I can.

Thanks again.

I replaced the shocks specifically because the information I was able to find indicated that the Bilstein shocks had greater damping ability (I.e. valved stiffer) than the stock Fox shocks.

I felt the stock suspension was both under sprung and under damped. The Bilstein shocks were about a 1/2 inch longer than stock FYI, I believe they are spec’d for stock to +1.5” of lift.

I’ve done more driving and am really liking the change; I had gotten to the point where I wasn’t looking forward to driving the truck.
Having to ‘grandma’ the truck over any minor obstacle on road was getting boring.

I can hit speed bumps without lifting the throttle now, not possible without slamming into the bump stops in the stock config.

As always, YMMV.

 

[BriGuy]

Thanks! I ordered ALL the stuff listed and it'll be here next week. Looking forward to installing as well. Can't wait for that rake to be gone and also to not bottom out

I almost lost my mind the first time I hit this small dip on a back road and the front end bottomed out with a nice hard SMACK...yikes.

 

[BriGuy]

Chiming back in to this thread to say thanks for the excellent research and parts list you provided. I put on these exact components this weekend and it's made a great difference in both ride and looks of the Jeep.

For sure this also provides enough room if someone wants to put 37s on someday as well.

Total cost for me was around $750 and well worth it!

Here are the before and after of mine.

 

[meckanik]

Chiming back in to this thread to say thanks for the excellent research and parts list you provided. I put on these exact components this weekend and it's made a great difference in both ride and looks of the Jeep.

For sure this also provides enough room if someone wants to put 37s on someday as well.

Total cost for me was around $750 and well worth it!

Here are the before and after of mine.

That's awesome, your truck looks much better and I'm glad you're enjoying the handling change.

On a side note, after driving mine more I'm seeing some slight porpoising which feels like the rear of the vehicle is just a bit under-valved. I think some slightly stiffer shocks in the back will help so I ordered matching Bilsteins for the rear.

I will update the first post once they are installed and I get some time on them.

 

[BriGuy]

Oh, I forgot to add that I did put on 4 shocks as part of this. For the little extra $ it seemed worthwhile.

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