A YJ Wrangler or MJ Commanche axle will also work for a spring under parts base. The spring width is different from the XJ (so the pads must be rewelded anyway) but the u-bolt and shock mount hardware makes the job easier. The D44 can handle a pavement ripper.
A combination of a short boomerang shackle and XJ main leaf with MJ second through forth leafs makes a good spring pack (with forward half stiffness to counter spring wrap induced wheel hop), leave out the overloads. The drop is ~3.5-4.5 inches. You have to make your own anti-sway bar link.
You can also simply remove rear leaves in the stock spring over pack, but the XJ owner's I have talked to prefer a long #2 add-a-leaf and the factory 2-3 leaf for a four leaf pack (dropping the two bottom leafs). The aal keeps the pack stiff for wheel hop prevention and firm static ride handling. Tha factory anti-sway bar link works in this configuration.
Front coils can be replaced with stock TJ coils for ~1.5-inch drop. Each stock coil loop cut is a ~2-inch drop. There is probably fifty pair of stock coils in list member garages available for the asking (cut a variety for spares and tuning).
Spring mods will put the axle on the factory stops.
Rear bumpstops can be cut with a hacksaw, or replaced with short stops. CJ front stops (~1-inch tall) are a near bolt on.
The 3-inch tall upper front stops can be removed completely and replaced with a very short (~1-inch) a-arm stop from a 70's F-body Chevy (Camaro/Nova). Rancho sells poly replacements for both ends that bolt-in.
A 4X4 needs to watch trackbar clearance on the diff cover (some hit, some miss). The UCA's & axle need carefull attention to the bumpstops to prevent hitting the oil pan & header.
Be aware the stops must function, as you will be on the stops often.
Tall rim & wide aspect ratio tires need fender clearance (just like big lug off-road rhinohides) so consider fenderwell bending of the leading and trailing edges. The serious fabricators pull the flares and cut to the double backed metal and then start the bending. Both flares may be raised ~1.5 inches if you really want to make compression room.
Adjust the steering stops to cut tire to control arm rub.
Good shocks are critical. You will want to place careful attention to length. Stud to eye conversion is almost required on the front to get a good match (let me know if you find another way).
High pressure gas shocks (Bilstein, Rancho RSX, or other) will help the ride. The low pressure gas shocks (the construction of almost every other shock) are not as good for road racing. The age related dead spot common in cellular gas type of shock construction works against you with the limited travel.
Watch the slip yoke plunge slack if you make an extreme drop.
Adjustable anti-sway bars (relocatable end links) can help tune the ride (what little ride there is). Think about poly bushings.
This is also one place where unmodified Rancho lower control arms work -- minimal travel and stiff bushing control of the axle (and boring the bushings to accept a larger diameter stock internal bushing sleeve helps even more -- or use Bill A's rubber bushing conversion).
Steering box brace is recommended if you really push the corners.
Think about a belly pan fairing for some ground effects and a slight rake. The high speed XJ also needs some rear end drag or rear roof lip spoiler to move the center of pressure back behind the CG (Stock XJ's are amazingly well balanced weight wise).
Have a lot of fun. The Archer brothers campaigned a few MJ's back in the mid/late 80's in the SCCA truck circuit (before NASCAR sponsored a truck series). Even with a straight axle (2WD) against Typhoon style IFS Blazers they were very competitive. There was a lot of development (at the time) by AMC and Walker Evans for the SCCA and MT/SCORE Stadium race series.
Happy Trails!
By Ed Stevens
, and the author of this tech article disclaim any and all liability associated with any "do it yourself" vehicle modifications and/or repairs.
Content © 1999- 2002 North American XJ Association
A combination of a short boomerang shackle and XJ main leaf with MJ second through forth leafs makes a good spring pack (with forward half stiffness to counter spring wrap induced wheel hop), leave out the overloads. The drop is ~3.5-4.5 inches. You have to make your own anti-sway bar link.
You can also simply remove rear leaves in the stock spring over pack, but the XJ owner's I have talked to prefer a long #2 add-a-leaf and the factory 2-3 leaf for a four leaf pack (dropping the two bottom leafs). The aal keeps the pack stiff for wheel hop prevention and firm static ride handling. Tha factory anti-sway bar link works in this configuration.
Front coils can be replaced with stock TJ coils for ~1.5-inch drop. Each stock coil loop cut is a ~2-inch drop. There is probably fifty pair of stock coils in list member garages available for the asking (cut a variety for spares and tuning).
Spring mods will put the axle on the factory stops.
Rear bumpstops can be cut with a hacksaw, or replaced with short stops. CJ front stops (~1-inch tall) are a near bolt on.
The 3-inch tall upper front stops can be removed completely and replaced with a very short (~1-inch) a-arm stop from a 70's F-body Chevy (Camaro/Nova). Rancho sells poly replacements for both ends that bolt-in.
A 4X4 needs to watch trackbar clearance on the diff cover (some hit, some miss). The UCA's & axle need carefull attention to the bumpstops to prevent hitting the oil pan & header.
Be aware the stops must function, as you will be on the stops often.
Tall rim & wide aspect ratio tires need fender clearance (just like big lug off-road rhinohides) so consider fenderwell bending of the leading and trailing edges. The serious fabricators pull the flares and cut to the double backed metal and then start the bending. Both flares may be raised ~1.5 inches if you really want to make compression room.
Adjust the steering stops to cut tire to control arm rub.
Good shocks are critical. You will want to place careful attention to length. Stud to eye conversion is almost required on the front to get a good match (let me know if you find another way).
High pressure gas shocks (Bilstein, Rancho RSX, or other) will help the ride. The low pressure gas shocks (the construction of almost every other shock) are not as good for road racing. The age related dead spot common in cellular gas type of shock construction works against you with the limited travel.
Watch the slip yoke plunge slack if you make an extreme drop.
Adjustable anti-sway bars (relocatable end links) can help tune the ride (what little ride there is). Think about poly bushings.
This is also one place where unmodified Rancho lower control arms work -- minimal travel and stiff bushing control of the axle (and boring the bushings to accept a larger diameter stock internal bushing sleeve helps even more -- or use Bill A's rubber bushing conversion).
Steering box brace is recommended if you really push the corners.
Think about a belly pan fairing for some ground effects and a slight rake. The high speed XJ also needs some rear end drag or rear roof lip spoiler to move the center of pressure back behind the CG (Stock XJ's are amazingly well balanced weight wise).
Have a lot of fun. The Archer brothers campaigned a few MJ's back in the mid/late 80's in the SCCA truck circuit (before NASCAR sponsored a truck series). Even with a straight axle (2WD) against Typhoon style IFS Blazers they were very competitive. There was a lot of development (at the time) by AMC and Walker Evans for the SCCA and MT/SCORE Stadium race series.
Happy Trails!
By Ed Stevens
, and the author of this tech article disclaim any and all liability associated with any "do it yourself" vehicle modifications and/or repairs. Content © 1999- 2002 North American XJ Association