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Rough ride after shocks and springs

c_woodruff91

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Putting "rough" in quotes because I've seen the FAQ on this, and it doesn't quite address what I mean. Rough might be the wrong word.

A few weeks ago I did shocks and springs on my TJ. TLDR: It sits about 3" higher in the rear, with no reciprocal lift in the front (will explain below). No change to tires or tire pressure. However, it now feels like there is significant drag, and also like I am constantly driving on a brick road. This is what I mean by rough: not maxing out the shocks too early, but lots of drag and vibration, especially under torque. I haven't felt comfortable taking it above 35mph.

Now for the context. First, I don't know what I'm doing, which will become abundantly clear. Second, I don't know exactly which moving parts will be relevant to the above issue, so I'll explain everything. Forgive the essay.

Springs I ordered OME springs, part numbers 2942 (rear) and 2933 (front). The front ones never arrived, hence the front springs haven't changed (yet), hence the above comment about lift in the rear but not the front. The rear springs I was replacing were stock, with a 1.25" spacer. The new OME's were advertised as TJ springs, but sat a full 3" taller than the stock ones, excluding spacer, so a net difference of +1.75". I didn't bother to reinstall the spacer since I was already getting that much of an increase. I did have to unbolt the rear track bar at the frame bracket to get this done (and it was a PITA to get back in).

Shocks I ordered Fox 2.0 shocks, part numbers 985-24-085 (rear) and 985-24-084 (front); advertised as being for TJs with a 0 - 2" lift. (I've got 2" spacers in the front, and again, previously had 1.25" in the rear.) Front shocks fit fine, end of story. The rear shocks were a full 4" SHORTER than the ones I pulled off, at full extension. Plus, I hadn't accounted for the additional lift from the new springs. So I returned these and bought part number 985-24-086 for a 2.5" - 3.5" lift. These still sat a little shy of 1" shorter than the old shocks. I was aggravated enough to just install them and see, though, and they don't appear to be overextended at ride height, even with the lift from the new springs.

Net effect:
* Rear springs replaced, and rear spring spacers removed
* Front springs untouched
* All 4 shocks replaced, but not two matching pairs
* Feels like I'm driving on bricks; errant vibration, lots of drag

"Replace the front springs, dummy" ? :) Thanks in advance.
 

rasband

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Did you verify that the rears were 2942 and not the HD 2949?
Doesn't matter, the springs won't make the ride "rough". All that means is the rear might sit slightly higher between the two springs.

Did you cycle your axles and set bump stops? It seems like your shocks aren't right for your setup or your bump stops aren't set right. I had an old set of fox shocks that rode nicely, but most folks with the newer sets don't like them.
 
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LONGJP2

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The issue is "rough" riding, not the obvious height difference since they've not put in the front springs they don't have yet.
The rear springs I was replacing were stock, with a 1.25" spacer. The new OME's were advertised as TJ springs, but sat a full 3" taller than the stock ones, excluding spacer, so a net difference of +1.75". I didn't bother to reinstall the spacer since I was already getting that much of an increase.
And taller springs. Hence my original question about receiving the correct ones.
 
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c_woodruff91

c_woodruff91

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Thanks for all the replies.

@LONGJP2 - Yeah, they were 2942s, just double checked the box. Is it expected that those would sit so much higher than stock? Pics here. No tape measure, but delta was 3".

@rasband "Did you cycle your axles and set bump stops?" — Nope. In fact, the bump stops aren't back in yet. Haven't been able to find the right length bolt to re-attach the cup, since the ones I pulled off were longer than stock, so to accommodate the spacers. Just to confirm though, this feels like sh*t going 30 on side streets, I'm not hitting any major bumps. Also, not sure what "cycle your axles" means... so gonna have to look into that one. Thanks.

@InOmaha Honestly yeah, feels like driveline vibration, just not sure the relationship between that and what I did.
 

InOmaha

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I have an unlimited and did the same lift. I got close to 4" with a body lift, but no vibrations. Did you do a track bar relication bracket or adjustable trackbar in the back?

I have more room to play with but I'm going to put on adjustable control arms to play with the pinion angle because any excess angle causes more wear and reduces efficiency. I'm an enguneer that looks for efficiency improvements so things bug me.

If you have a regular TJ, you may need a SYE and a new drive shaft. Try a MML first, a transfer case drop until you can figure it out second.
 
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c_woodruff91

c_woodruff91

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Nah I didn't do anything with the track bar. I didn't think I'd need to, because I didn't intend to get significantly more lift. (The rear was sagging, so I figured I'd get some but not 3"). But I apparently don't know what to look for to find springs that are more-or-less OEM specs, as evidenced by this experience with the OME 2942s.

Now that I'm writing this all out, I'm wondering if the whole problem in the first place was a mismatch between shock length and spring height by whoever did the original leveling kit. The shocks did need to be replaced, but also I would bottom out occasionally and the passenger rear bump stop was completely gone. Given that the Fox 985-24-085 pair I started with was so much shorter than the shocks I pulled off, I wonder if the original shocks were too big in the first place, which would then have been riding too close to minimum extension based on the original spring height.

Does that make sense? If so, I wonder if it's best to go back to Fox 985-24-085, plus original springs and spacers. No additional lift, but potentially more appropriate shock + spring height match. One problem at a time.
 
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c_woodruff91

c_woodruff91

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Just took a look at the old shocks and pretty sure the model number is 658696. If I Google:
jeep tj rear shock "658696"

I get a bunch of results for a Rough Country 4" lift kit. If those are really the same shocks, then that's clearly wrong for stock springs with 1.25" spacer lift. Also, track bar looks stock, no existing relocation bracket.

Old shocks measure 25.5" at full extension. Old springs measure 12.5", plus 1.25" spacer = 13.75"
 
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Mike_H

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You can't judge what the rear is going to do until you put the front springs in. Forget about the shocks for a minute. once you get your ride height established, then go looking for the correct length shock.

I do know of one other guy that ended up with more lift from the OME springs than what was expected. It was a while ago and he had to replace the springs.

The resistance and vibration you're feeling is probably the rear driveshaft binding
 
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c_woodruff91

c_woodruff91

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I wound up going back to the original springs. The shocks were the real impetus for the project, just thought I'd do springs while I was in there. Get something with a higher rating and maybe alleviate some sag in the rear. Never meant to add 3".

All in all, replaced 4 shocks, steering stabilizer, and rear jounce cups and bump stops. It rides pretty damn well now.

Still stumped about why all this stuff is advertised the way that it is. OME 2942s for sale. ;-)
 
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jjvw

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I wound up going back to the original springs. The shocks were the real impetus for the project, just thought I'd do springs while I was in there. Get something with a higher rating and maybe alleviate some sag in the rear. Never meant to add 3".

All in all, replaced 4 shocks, steering stabilizer, and rear jounce cups and bump stops. It rides pretty damn well now.

Still stumped about why all this stuff is advertised the way that it is. OME 2942s for sale. ;-)
What was the change in ride height?
 

freedom_in_4low

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If you look at the spring rate table that floats around here, OMEs are pretty high, so it wouldn't surprise me at all to get more lift than advertised when installed on a lighter rig. Maybe it's the Australian thing... Their style of preparation looks heavier than ours.
 

jjvw

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If you look at the spring rate table that floats around here, OMEs are pretty high, so it wouldn't surprise me at all to get more lift than advertised when installed on a lighter rig. Maybe it's the Australian thing... Their style of preparation looks heavier than ours.
Australians carry a lot of crap with them.
 
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