Cold weather performance of rear springs?

This is the first winter I've owned my XJ (99 Sport model with the upcountry package.) And it rides super rough. Even the frost heaves in the road send the rear end up into the body like I'm landing a Dukes of Hazzard jump.

The shocks are some sort of aftermarket Monroe that's painted silver. They seem relatively new.

The springs back there look done to me. Someone told me they're supposed to be flat like that though in the Sport model. In the spring/summer/fall the jeep rode fine though. How much beating should I put up with in the cabin? My friend has a lower mile 99 SE model and his rides like a Buick compared to mine.

I should also add that I have a dual 10" subwoofer box back there that weighs about 100 pounds.

I deflated the rear tires to 32psi down from 38 because I couldn't take it. It still rides nearly as rough.

On the passenger side, the long bump stop is missing. The rubber part came free from the mount due to rust it appears.

My next question could probably be answered in a search, but is it OK to put regular, non sport model springs in it? I don't need the jeep to corner like a sports car. I want it to ride comfortably around town and on the highway and occasionally drive me across an Iowan field to a farm pond. Will it sit goofy with U shaped springs back there?

Here's a recent photo of the current stance. I can fit about four fingers between the rear tire and the fender on one side and about three fingers on the other side. I've got 235/75/15 snow tires on there right now.




I'm just curious if the springs get to the point where they NEED to be changed. It feels like I've got things welded solid back there at times.

I couldn't find the icon to edit my first post, sorry..

Here's some photos I just took to show the driver vs passenger side height as well as the passenger side spring situation.

Driver side looks about like any other XJ I see driving around town


Passenger side looks lower than it should be to me


This is the spring on the passenger side. It almost looks flat if not bent upwards slightly. The bumpstop corrosion is seen as well.

Looks like you just need new springs to me, also replace those bumpstops and you won't feel like you're bouncing off the planet anymore. My rig was in the same condition as yours till I replaced the springs, still haven't replaced the bumpstops, need to figure out what height I need to keep my new tires out of the wheel wells before I buy anything.

luketrash said:

....it rides super rough. ..

Click to expand...

That would be your shocks. And maybe your tire pressure. 30 psi is OK, 38 psi is way to high.

A flat spring rides smoother than an arched spring. Your UpCountry springs are sagged. Keep in mind if you buy replacement springs, that the UpCountry springs are 1 inch taller than stock springs and you will need to buy new UpCountry springs or a replacement spring that is taller than stock.

I see springs that add 1.5" to stock height. Are those the ones I should be looking for? I'll have to search through here.. Somewhere there's a good writeup on part numbers. That or just call some of these jeep supply catalog companies and ask them for opinions. I wouldn't be that disappointed if the back end ended up givng the jeep some rake if it was slightly too high, but I don't want to go overboard.

The shocks are Monroe Reflex I believe.. In the silver colored housing.

Check your shocks.

Drive it for about 10 minutes, feel how warm they are.
cold=worn out, warm= normal, hot= seized. iirc

you may also have a cracked spring

as a side note, i installed some monroe sensa-tracs (supposedly ride smoother than the more 'truck' oriented reflex shocks you have) to replace my blown out stock shocks. the stock shocks rode like a caddy, but it leaned hard in turns and just doing something like driving off a curb at an angle would rock the entire body pretty hard. Once i put in the new shocks, the bumps became MUCH more apparent, much less lean in turns ect ect. So i think a lot of your ride comfort is coming from your rear shocks.

also my rear springs are in the same shape as yours, and looking at the bushings for the spring/rear shackles/control arms, they are all original and very cracked/hard dry looking. I hope to reclaim some ride comfort back by replacing these but i'm not holding my breath. I think it should help though, the old ones just seem like they are so hard and compressed that new rubber would almost HAVE to help. If anyone has an input on this please speak up.

remember too, in the winter, shocks run stiffer, and all the rubber is stiffer. So it generally rides a bit rougher in winter, i've found this w/ most cars.

I should mention that the temperature here hasn't been over 10F in a couple weeks. The high temperature Friday is -4.

My truck rode better lifted because it wasnt sitting so close to the bumpstops. If you use your truck lightly, it might be ok to run blocks to try to get rideheight back to where it belongs.

Also, your winterforce tires are mounted backwards. Theyre directional

luketrash said:

... 99 Sport model with the upcountry package....

My friend has a lower mile 99 SE model and his rides like a Buick compared to mine.
... is it OK to put regular, non sport model springs in it? I don't need the jeep to corner like a sports car.

I deflated the rear tires to 32psi down from 38 because I couldn't take it. It still rides nearly as rough.

Click to expand...

Up Country package consists of 1 inch taller springs and NO rear sway bar. I don't know if the springs are firmer though.
"Sport" model is just a trim level. On my '96 it's between my SE and Limited or whatever is "highest".
2X on letting a bit more air out of the tires. When I got my A/T tires installed they put in 38 pounds, just a terrible ride. Now I'm down to 28, much better ride and handling and they wear evenly. But, A/T tires do ride harder than "street" tires.

Take note though, he is running winter tires right now, that even in low temps, will ride ultra soft.

I think priority number 1 is getting that bump stop replaced. They add some slight progressive damping when the axle hits them, although they could have designed them better. In frost heave season you will hit the stops occasionally no matter what shape everything is in, and without that stop there, it will hammer you to death. Second job is to check the shocks. Don't judge by looks. Third would be to do something about the spring sag, perhaps adding a leaf.

Thanks for the suggestions!

Yeah, the tires I have on there right now are Firestone Winterforce. They've got fairly soft sidewalls and the tread is obviously softer than AT tires. As cold as it is here, everything is pretty hard right now though.

Since I'm only driving it in town, I might let more air out to see if that helps. I'm running really worn Bridgestone Dueler AT tires at 45 pounds in the summer and it rode fine then (well fine as in not bottoming harshly.)

And yes, I am lacking a rear sway bar and have a steel plate covering the fuel tank as well as a drawbar back there. Since I have the skid plate up front and a transmission cooler I figured I had the upcountry package or a tow package of some sort. My jeep does not have a cruise control installed. And it does have a limted slip Dana 35 back there. If I'm remembering right, that combo pointed to the upcountry package.

Replace that bump-stop and then add the two main leafs from a set of discarded stock packs to your existing packs.

If it ends up you're looking just a shade high in back, toss in another pair of isolators up front.

If you're still ridin' a bit rough, look at replacing those shocks.

Gonna' look great with those 235s', too...

I think it may be a combination of sagged out springs joyncing you off the bump stop/ bottoming out the shock, new springs should help, replace the bump stop. shocks could still be good just bottoming out

I wondered about that as well. It's hard to see in the photo, but the rear end doesn't appear to ever physically hit where the bumpstop is. It might be the shock itself bottoming (which I'm sure is horrible for them.)

Once we get some warmth back here I'll get cracking. I can start my regimen of PB blasting everything now and it should be ready by April

She's sittin rather low for Upcountry. Our '96 actually looks lifted, but it's not, just stock Upcountry, which was 1" lift. Do you still have the stock, upside-down shocks on it? On our other three Down-Country xjs, we have SensaTracs, they're firm, but I wouldn't call them harsh. Yeah, any shock will stiffen up in cold weather, but I'll bet yours have a lot of miles on them, and they're shot. Some shocks turn into limp noodles when they're gone, but some stiffen up pretty bad. My money's on needing shocks, and my vote is SensaTrac for on-road driving. And with good shocks, you maybe won't be hitting bump stops so often.