Replacing stock TJ coil springs

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rickbyrne
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Replacing stock TJ coil springs

Post by rickbyrne » Thu Nov 02, 2017 11:01 am

I'm wanting to replace the stock 97' coil springs on my Sahara TJ. Can I replace with 2.5" lift coil springs from Skyjacker without needing to add anything else? Already have some Skyjacker shocks rated for 1-3" lifts installed.

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wdln
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Re: Replacing stock TJ coil springs

Post by wdln » Thu Nov 02, 2017 4:24 pm

Oddly, I just did this exact thing last weekend on a stock '05 TJ. I'll tell you what my experience was and you can decide for yourself.

We put in a 2.5" Rough Country lift which consisted of replacement springs and longer shocks. The salesman who worked with my buddy (the Jeep's owner) said they were not sure if we would need track bar relocation brackets, so he bought them just to be sure. We got the springs and shocks put on and both axles were visibly laterally misaligned because of the now-too-short track bar, so we put the relocation brackets on and the axle/wheel position looked much better. These required some drilling and the rear was somewhat difficult to install. The stock front sway bar links were also difficult to get reconnected with the extra lift. This process took us (4 guys) about 8-9 hours but we did have one wheel that sheared off 4 of the 5 lugs when we took it off.

I took before and after measurements, and the front ended up netting 4.5 inches of lift and the rear had 2.5 inches. The Jeep appeared to be sitting level. Although it only had 65k miles, I assume the stock front springs must have been worn and squished down. Or, do stock TJ's have a forward rake where the front end is lower and this also levels it out? Not sure. Measurements at the fender well and the bumper both showed a 4.5" effective lift (tires stayed the same).

Everything looked good until the test drive. There was rear driveline vibration between 20 and 45mph, then it would subside above that. Steering was twitchy too. I suggested a transfer case drop using small sections of pipe to drop the skid plate. This fixed the rear vibration issues but the (manual) shifter was then hitting the plastic trim in the "down" gears (2, 4, and R). Removed it, and the boot, and it was fine. On the next drive, there was bad death wobble. We were able to replicate it over and over... you'd hit a bump and the front would start oscillating. I checked toe-in and it was way off... 1.5 inches (should be 1/8"). My crude estimation of the caster angle was around 3 degrees; it's supposed to be 5-6. I couldn't adjust the caster, but I did get the toe-in pretty close. That didn't help the death wobble. There are lots of different things that can cause it.

I was out of time, parts and ideas at that point so the owner ended up taking it to a shop. They welded the track bar brackets in place, put in longer sway bar links, and performed an alignment, although I'm not sure they could fix the caster angle without adjustable control arms so that may be the same. The owner said the death wobble seems to be gone but he has yet to get it up to true highway speed. He also has yet to solve the shifter issue; I think we're going to try to bend it so it will fit around the trim and have the handle be in a better position for the driver.

So to sum up, what the sales guy said was that we MIGHT need track bar relocation brackets along with the springs and shocks in the kit, but in reality there was a bunch of other stuff that needed modification or replacement. A mild lift on an older Jeep that drives fine in stock form might bring out all issues with weak and worn parts of the suspension and cause drivability problems.
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Re: Replacing stock TJ coil springs

Post by Fraser » Fri Nov 03, 2017 9:45 am

Dave - kudos on quite possibly the most complete answer on here. For what it's worth, my guess is your buddy's TJ has some other worn front end component contributing to the death wobble. It doesn't take much wear to cause issues.
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Re: Replacing stock TJ coil springs

Post by rickbyrne » Sun Nov 05, 2017 6:32 am

That was an extremely helpful response and leads me away from making a quick decision. Going to do some more research this winter. Also sounds like you’ve got some great support around you.

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Re: Replacing stock TJ coil springs

Post by wdln » Thu Nov 09, 2017 1:31 pm

Glad I could help. Or more accurately, I'm glad my friend's misery could be of service. :D

Just to follow up, I found out today that the death wobble is back after all the other work that was done. The shop he took it to is now recommending a whole new sway bar (not just links) and new tires as well.
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Re: Replacing stock TJ coil springs

Post by Duke Winch » Fri Nov 10, 2017 11:46 am

Can't speak for Skyjacker but have had good success with Rubicon Express. As Dave eluded, it's more complicated than just installing longer springs and shocks. You need the ability to adjust both front and rear track bars along with front caster and rear pinion angles.

(I'm not sure why the shop would want to replace the sway bar mentioned in Dave's post)

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