b00128806

I’ve read about the 9/16 grade 8 bolt upgrade a long time ago and I refused to believe that “0.011” inch would make a difference in handling. Also, engineers are very detailed in specifying fasteners bolts.

Well I just did it and I take that back, EVERY STOCK/MODIFIED JEEP SHOULD DO THIS UPGRADE.

My Jeep never handled well (stock setup), and I’ve driven a lot of front solid axle vehicles. Steering was very “darty” and required constant 2 hand adjustment. On rough roads the handling was horrific. The best way to describe the handling is it felt like the jeep did not have shocks. The up/down felt like the suspension bottoms every time. Also, there is a lot of side-to-side lateral movement of the axle whenever I hit any road imperfection on one wheel. This would jerk the steering wheel to one side if it was the front axle and push the tail of the jeep to one side if it was the back axle. Any speed above 60mph would just feel very unstable (white knuckle uncomfortable), too much vibration coupled of the darty steering and the lateral movement on potholes and I was never able to drive the jeep comfortably on the highway.

I’ve made some modifications to try to remedy this:

- Bilstein Steering stabilizer.

- Bilstein 4600 shocks (stock height).

- 275/65R18 (slightly wider tire but same height).

- Tightened the steering gear box.

The stabilizer bar helped with the steering on mild road imperfections. The shocks also helped since they are valved slightly stiffer than stock. But I could never really get rid of the lateral axle movement on rough roads or the vibrations at highway speeds. Whatever gains I made were wiped out by going to a heavier tire as I moved to an LT from a P.

I chalked that up to the fact I opted for the tow package which came with stiffer springs and the jeep was rarely loaded (Jeep does handle much better loaded). Or maybe my jeep was built on a Friday before the long weekend.

Finally, decided to do the bolt upgrade. I couldn’t get any of the kits online shipped to me, so I printed the parts list from the synergy kit 8050, I went to the local hardware store. The list calls for fine thread UNF, but I couldn’t find any. I ended up buying the bolts with coarse thread (UNC). The only difference is the clamp loading on the fine thread is ~11% higher so you should absolutely buy the fine thread. I adjusted my torque value to 115 lbs.ft for the grade 8 plated new bolts. The fine thread torque value is 129lbs.ft for the plated grade 8 which is closer to the M14 fine thread stock bolts 125lbs.ft. I also opted for the nylon locknuts since they can handle vibrations better.

I figured I’ll start with the easiest ones to change and work my way to see the impact each would have.

- - Front lower control arms

This was very straight forward. Taking the stock bolts out to see how loose it sits in the sleeve and yeah, the 0.011 inch is significant. There were some thread score marks in the sleeve but not too significant. I did these first and went to test drive. I wanted to remove any possible placebo effect so went on a 2-hour drive looking to hit every road imperfection I can find. I hit some pretty significant potholes. The steering wheel jerk on potholes was gone also no more “dartiness” in steering, the jeep tracked much better and felt like its more buttoned up. On acceleration the jeep was dead straight with 1 hand on the wheel. One thing I noticed is the significant reduction of drive line vibrations. I picked up speed on the same roads because the jeep feels so much more stable. The steering no longer wanders, this was instantly noticeable. The front axle lateral was all but eliminated except for very large potholes. I figured this will be truly eliminated for changing the front trackbar. The stability on gravel roads is improved by about 1000%.

Don’t make the mistake of thinking this turned into an IPS, this is still solid axle. But for a solid axle front this is DARN DECENT handling I was thinking to myself I can live with just this day to day. I have barely begun. This was just the front lower control arms. I’m not much of an expert on alignment but I can see why lifted jeeps always change the lower control arm first if they are on a budget.

- - Back lower control arms.

I changed them out and went for a test drive. One thing to note is my passenger side control arm was harder to align the bolt through, it was off by a good 1/8th of an inch. I don’t know why or what it means but I just wanted to test it. Same thing 2-hour road abuse. First thing I noticed is, I can finally feel my shocks working, you feel that slow up/down wave go through the suspension when you hit a road imperfection "the boaty" feel but totally controlled. The bottoming out feeling was reduced to nothing but still there on monster pothole, we got a lot of the filling loosening ones. The ride felt so controlled and tight. Definite improvement in cornering speed with the back control arm bolts swapped.

So, with both front and back lower control arms swapped out the biggest difference is highway driving. I was going 80 miles an hour with 1 hand on the steering wheel. This I have not done with the Jeep since I bought it. The straight-line highway driving is night and day different. I'm happy i got my 1 handed driving back.

I just stopped after that to get ready for the track bars next. I want to get used to the way it drives now so I can better test the difference. I’ll re-post once I’ve done the upper control arms and the track bars.

I’m just speechless. I can’t believe I lived with the garbage handling for 7 years. I can’t believe Jeep would put this purposefully. Every bolt is pretty much the full thread metric style. I sure would like to hear an explanation from @Jeepcares as to why these bolts where specified. This can not be a mistake, these bolts are also used in the JLs.

Kudos to all the guys that posted this for years. This is the best $90 modification I’ve done to the jeep. I just figured it wouldn’t be spent fixing Jeep design shortcoming.

Mark Doiron

I just had the axles on my Jeep replaced (Dyna 44 on front, Dyna 62 on rear--62 is a 60 with a couple small changes). I had never done the bolt kit upgrade; my OEM hardware was working just fine at over 280,000 miles. However, since my mechanic was pulling the axles loosening all of that hardware anyway (along with new control arms except for the front uppers), I figured may as well add the bolt kit to make his work a bit easier. The calcium chloride used on roads in Alaska and Canada I've driven is infamous for causing corrosion.

Sixty4x4

Some good info there but not sure how those bolts could make a difference as mine had no slop and any tighter andI would be hammering them into place. I have the 2.5" lift and other good stuff there and mine rides without the issues you describe. IEdrives with 1 hand at any speed.

PS: can one still drive to the dunes from the start of the ice road?

b00128806

cant figure out why 9/16th bolt would tighten handling so much. The slop in the bushing sleeve is definitely there.it might have gotten worst with time but jeep always drove sloppy. Im suspecting the 1/8th of an inch offset on the passenger side might have something to do with it but I'm no alignment expert. I initially thought one of these bolts might be loose, but it took some serious effort to break all the ones I replaced.

Im still not sure how this worked out at all.

b00128806

quick update

-- front and back upper control arms

i changed out the upper front and back control arms as well. These where a b**** to change especially the ones with the welded nuts. No noticeable difference in handling at all. I don't know why but the lower control arm bolt change out made the biggest difference.

-- front and back track bars

Changing these made the jeep track better on smooth roads. The lateral jerk when hitting ruts in the road is reduced. The jeep follows ruts in the road less on the straight aways. Still not as much of an impact that the lower control arms bolt change out made.

over all changing the front bolts made the biggest difference and changing the lower control arm bolts made the biggest difference.

note on the UNC vs UNF. I was worried that the coarse thread bolts would loosen with time. But the nylon nut seems to do the trick. Checked the bolts where where all still tight to spec.