Rally mods

Okay, new guy here, 1st post. In fact I don't even own an XJ yet, currently shopping. (Do own a fully modded TJ tho)

I've been rallycrossing an Evo and have decided to sell it and build a competition XJ. Since I know very little about these cars, maybe some of you can help bring me up to speed. I choose the XJ because I saw one running stock class at a major race and was impressed. And it's cheap. And I can build it much more durable than the Evo, Sube set which means I can keep my foot down where they lift.

Will be in Mod-4 class which means I can do most anything as long as I meet safety rules. Which is my first challenge. Lifted vehicles are not allowed, including lift just due to larger tires. You can agree or not, but them's the rules. I want to build the truck in stages because I prefer driving to building.

So Stage 1. Lower about an inch so I can fit some decent tires to an otherwise stock rig. I might technically not even need to lower, but I will just to please the "safety police". Trucks and SUV's have a bad rep because of how often they roll in competition. I'll be running 26" tires on 15's and 16's because I have a garage full of dirt tires that size from my Evo. Other threads have mentioned TJ 4-cyl springs and also Eibachs. Not so many good ideas for the rear, except custom leafs. Bilstein 46mm HD shocks. Attention to bumpstops and limit straps and good to go. Will probably gut it mercilessly at this point (trailered racecar, no street). All the interior, bumpers and whatever else I don't need. Any idea of how light I can get it doing this? The Evo was a porker at 3600 lbs.

I've lots of ideas for Stage 2 and beyond, but I want to hear what you guys think. And I'll be keeping an eye out for suitable used parts but have nothing immediately in mind. I'm especially interested in hearing from XJ desert racers, JeepSpeed etc, because eventually mine will look like theirs except lower.

Thanks, Bill

A few years ago there was a kid from Maine on the forum who had a stock XJ and raced it in a rally series up there with some simple engine mods and what i believe was completely stock suspension. I think it's a great idea but unfortunately i can't offer you much advice.

There's a guy on here who rallies an MJ. I think his threads are in the street and performance section.

Thanks for the links -- everything is interesting at this point. But for those who don't know, rallycross is a totally different animal than stage rally. Think of it as autocross on dirt.

In shopping for a candidate, are there any year or model changes I should be aware of? I gather the High Output engine started in 91 so shouldn't go older than that. Did later models get bigger or heavier?

They are al the same as far as dimensions. 97-01 is when the body style was updated.

Many people like the 99, it has the best head, high pinion front axle, and it has the high flow intake.

Also the 00-01XJ have the precat's in the exhaust system which generate a bunch of heat under the hood. I doubt that would be desireable for any kind of racing.

I'd aim for a 95 or a 99, in either case with the chrysler rearend not the dana 35.

You can argue lift a bit on XJs since some of them came stock with the UpCountry suspension. For racing you are going to want to keep your COG fairly low anyways, but the UpCountry suspension was about an inch taller than regular stock XJs. People have fit 37s on 2" of lift (so about 6.5" of overall lift, I guess) and 30s fit on a stock height rig with a bit of trimming for uptravel, which would give you about the same overall lift as an UpCountry XJ.

My leaning (if they actually get out a tape measure) would be to get an UpCountry XJ so your VIN says it has UpCountry (and thus the lift is stock), then lower it an inch using regular stock springs and put 30s on it.

For what you're saying, rally on dirt, I don't see a reason you'd need big tires and a lift anyways, since you'll be competing against mostly smaller lower vehicles you will have a clearance advantage right off the bat.

Set the swaybars up how you want them, get shocks that'll make it ride right across the type of bumps you expect at a speed you expect, get good grippy tires, some stock skidplates just in case, maybe a V8 ZJ tie rod for insurance, lockers if you feel like it, and have a blast.

There was a change from fiberglass to steel rear hatch at some point and also the door got more reinforcements in 94 I think?

I would look for wheel spacers for sure. I've done a lot of dirt logging road running in an XJ with my beater jeeps and the only thing I would want is more width for stability. I think you're onto it with lowering the jeep a little. they usually sit pretty low due to old age already. once the rear springs get old they break pretty easily from my experience.

you're going to want a steel gas tank skid if youre sitting lower and hitting some jumps.

i broke a motor mount while ripping around the fields one time, but other than that, nothing else!

some XJs had ABS and some didn't. all of them had drums in the back, and the upgrade to rear discs with grand cherokee parts is pretty simple.

good point on the motor mounts... get a set of brown dog motor mounts, a good quality transmission mount, and an aftermarket transmission crossmember. The stock crossmember is basically pressed sheetmetal and they are easily bent, "customized", and otherwise mangled.

Out of all the stock xjs I've driven (2 90 autos, 1 90 5spd, 92 auto, 95 5 spd, 97 5spd) the 95 5 speed seamed to be the fastest. If your going on a budget here is my idea (keep in mind I have NO rally experiance but just going on your thoughts):
A 95 xj 5 speed
Swap out the axles for ones out of a 98ish auto for the 3.55 gears (you will get better take off, dunno if you will need the little you might loose in deep 5th), better ujoints and 29spl 8.25.
You could do an easy rear disc brake set up with either liberty or grand brakes
Run 235's/26" tires with wider rims (cut the fenders if you have to, that's less weight anyway right?)
Grab stock front and gas tank skids
Do a v8 zj tie rod (I've bent stock tie rods with stock tires)
I would then spend all the money you saved on good shocks and maybe giving both axles some truss/support since I imagine some jumps are inevitable
Maybe do a racing clutch too

Like I said no rally experience just know how to build a cheap Cherokee lol

edit: as far as engine work I know someone built an xj on here for the Lemons race. Check to see what they did for cheap engine and drive train stuff.

You guys have a pretty good idea of what I'm after. However regards gearing, it's much more important to have a single gear to run in, than low launch gears. For that I'll need a gear that will top out right at 60mph, which of course will also depend on tires. I'll have to look up the ratios and do the math. Having the right gear is more important than stick or automatic. Of course I could change out the R&P's but that gets pricey compared to just buying the right package to start with.

It's commonly thought that smaller tires work the dirt better than big. I don't know if I agree. But the very best competition tires are rally gravel tires and by FIA regulation they're not allowed to be bigger than 26". Could you do just as well with 30" or 31" extreme traction 10-plys? I think so.

I've got an extra set of Rubicon Moabs sitting around. I'd probably want to run quality spacers with those to get a wider track. Moabs have kind of a narrow offset. A little wide for my rally tires too, but it's what I have.

Do you plan on just sticking in local and regional events, or do you plan on taking a crack at Nat's?

Also, what region are you racing in? This will be important for setting suspension, gearing, etc.

What surface are you most likely going to be racing on? Hardpack clay, sandy, tarmac, gravel, loam, etc?

Are the rules for Mod about as free as the same classes in Solo2? This could be fun!

edit - also what is your driving style?

i plan on setting up a MJ for tarmac eventually.. so i've given this a lot of thought.

get a pre 96, OBDI. lighter, easier to mess with.

TJ coils will drop you, but keep you at the same rate. so, i'd cut a coil off the stock XJ spring to lower it and stiffen it up a tad. for the rear, flip the perches, go spring under. shocks, you'll want stiff as well, but you want top match the rate or the springs too... i'd try and get a set on the stiffer side... maybe koni adjustables, or bilstein 5150s, 255/70 valving. they make 6.5" travel ones now, so those "might" work with stock height XJs or a tad lower. swaybars are tough with dirt.. i'd roll with the stock ones and get a feel for it and see if you want bigger ones front or back to get you more sideways/less sideways.

i didnt catch if youre running 2wd or 4wd.. not that it matters much. but i'd get some STIFF aftermarket arms. catch a rock or rut the wrong way in a rallyx and you XXXX up your car bad.. something like ironman 4x4 fixed uppers and lowers with poly bushings. he can make you stock size replacements i'd reckon, he's pretty popular around here. trackbar? you'll want something a bit beefier, maybe a JKS or even something from ironman again. you're lower so you need to make sure it'll clear the diff.

wheels/tires... get a set of light alloys thatll work with the rally tires you have, might as well use em. the small tires will get you going quick. auto or manual? manual 3.73 gears and auto 4.10s will keep you in power no matter the gear. 2.5 I4 or 4.0 I6 btw?

I've been doing this a while. I ran both Colorado Nationals. Tennessee was too far a tow from California.

In Cali, there are two sanctioning bodies, SCCA and California Rally Series. They hate each others rules, so I have separate wheels & tires for each. You're kinda wrong about where you live being important for setup. I run events all over the western states and you get to see it all. Maybe if you never left town...

Mod rules are more open than Solo. In fact in CRS there virtually are no rules except you gotta be production-based and stay safe enough to keep the event insurance company happy. Rally car guys don't like offroad truck guys because they come out all caged and don't really care what happens. But rollovers (even "safe" rollovers) run the risk of our losing our sanctions. I've seen multiple serious race trucks flop it in the first corner. It's a different sport.

I'm a long-time autocrosser. Been to nationals 30 years and won many of them. So my dirt style is patterned after my autox style. You go with what you know. That means tight, late apexes and car control vs whoopee drifting. Which by the way works fine for many people. But I usually beat them.

BLine is a forum user here and he rally-x's his '96 Cherokee. Send him a pm if you want to and he could answer any questions you might have.

WAM174 said:

I've been doing this a while. I ran both Colorado Nationals. Tennessee was too far a tow from California.

In Cali, there are two sanctioning bodies, SCCA and California Rally Series. They hate each others rules, so I have separate wheels & tires for each. You're kinda wrong about where you live being important for setup. I run events all over the western states and you get to see it all. Maybe if you never left town...

Mod rules are more open than Solo. In fact in CRS there virtually are no rules except you gotta be production-based and stay safe enough to keep the event insurance company happy. Rally car guys don't like offroad truck guys because they come out all caged and don't really care what happens. But rollovers (even "safe" rollovers) run the risk of our losing our sanctions. I've seen multiple serious race trucks flop it in the first corner. It's a different sport.

I'm a long-time autocrosser. Been to nationals 30 years and won many of them. So my dirt style is patterned after my autox style. You go with what you know. That means tight, late apexes and car control vs whoopee drifting. Which by the way works fine for many people. But I usually beat them.

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I was unaware of your experience, and I figured you didn't know it all already... and people wonder why I don't miss auto-x.

So, that being said, what exactly are you wanting to know?

Here's a couple of threads that might have some useful info for you:

Lowering (long, old, more current posts in the last few pages, and snippets from the other 2 threads)
http://www.naxja.org/forum/showthread.php?t=8655&page=19

GRMS $2010 challenge XJ
http://www.jeepsunlimited.com/forums/showthread.php?p=4646132#post4646132

24 Hours of Lemons XJ
http://www.naxja.org/forum/showthread.php?t=1015631

There's another guy around here who was, I think, also doing some rally cross. -edit, no I think that was just in his sig. Search and you can probably find it- there aren't that many guys on here doing it.

Odd ball idea, but have you considered a 4-cyl XJ? Sounds like you're going for all-out handling. The only major down-side of the 4.0 is it's weight. They weigh more then most V-8s, and worse yet, because of the length of the motor, a big part of that weight is ahead of the front axle.

Build up a 2.5, bump the compression, more aggressive cam, bigger TB, injectors, a decent exhaust,... probably can't get up to the 177- to 196HP the various 4.0s put out without blowing serious coin, but 160 is probably doable, and 160 HP with a couple hundred pounds cut off the nose might be quicker on a tight course.

Whatever you decide on, look for a NP-242 select-trac transfer case. The full-time 4wd system with the center differential should handle better then the part-time system.

Corprin said:

So, that being said, what exactly are you wanting to know?

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You guys have been doing fine. I needed to know if certain years/models were a better choice than others. And the tips on motor and transmission mounts are spot on -- that's exactly the type of failures typical in RallyX. Many a car has gone home with the engine held in with ratchet straps.

I guess one thing not yet clear is how to lower the rear only an inch. Obviously I can write Deaver a big check. Or I might get away with doing nothing if I stay with the smaller tires. I'm finding the stock diameters range from 27" in '91 to 28" in '01. So with 26's I'm automatically lowered.

Can we say with any certainty what the normal transmission and axle ratios are in 91+ XJ's? Maybe there's a good table that lists them all? Since I want to do 60mph at maybe 5000 rpm (5500? what's a good/safe max?), that would be the same as 30mph at 2500rpm. That match up to anyone's car?