Spec 92-96 Jeep Gr Cherokee 4.0L/90-06 CJ/DJ/Wrangler 4.0L Steel Flywheel
The SPEC SJ40S is a billet steel flywheel for manual-transmission Jeeps with the 4.0L inline six: the YJ and TJ Wrangler, the Cherokee and Grand Cherokee, and the Comanche and Wagoneer. Jeep owners usually look for it when the old flywheel is cracked, hot-spotted or too thin to resurface, when takeoff chatters on a new clutch, or when a SPEC performance clutch is going in for big tires, low gears and hard trail use.
The flywheel bolts to the back of the 4.0L crankshaft and gives the clutch disc its friction face. It also carries the starter ring gear and stores rotating mass, which matters off road: a heavier flywheel helps the engine pull through rocks at idle without stalling. SPEC lists the SJ40S at 25 lb, a full steel part rather than a lightweight race piece, so it suits crawling, towing and daily driving. SPEC's 4.0L clutch kits for these Jeeps run from the SD651 Stage 1 at 401 ft-lb through SD652, SD653H, SD653, SD653F and SD654 up to the SD655 Stage 5 at 768 ft-lb, and SPEC lists this as the steel flywheel on those application pages. A new flat surface also gives any new disc the best chance to bed in evenly.
Rule out the hydraulics first. A low reservoir or a leaking master or slave cylinder makes the clutch drag or slip and a flywheel will not fix it. If the rpm climbs in a high gear while the Jeep does not accelerate, the disc is slipping; our slipping diagnosis guide covers the test, and the clutch chatter guide covers takeoff shudder. Once the transmission is out, use the resurface versus replace guide to judge the old part.
Our title reads 1992-1996 Grand Cherokee 4.0L and 1990-2006 CJ/DJ/Wrangler 4.0L. SPEC's own list for SJ40S is more specific: Cherokee and Grand Cherokee 4.0L from 1990 to 2005, Comanche, Wagoneer and Grand Wagoneer 4.0L in 1993, YJ Wrangler 4.0L from 1990 to 1993, and TJ and YJ Wrangler 4.0L from 1994 to 2006. SPEC does not list CJ or DJ models, so treat that part of the title as the catalog grouping, not a fit. It is for manual-transmission 4.0L Jeeps only; automatics use a flexplate. These Jeeps used the AX15 and later the NV3550 and NSG370 manual gearboxes, and our AX15 versus NSG370 guide helps identify yours. If you are unsure, send us the year and VIN before ordering.
Support the transfer case and transmission together on a jack, then check the rear main seal while the crank flange is exposed. Replace the crankshaft pilot bearing every time, using a puller such as the OEMTools pilot bearing puller. Clean the crank flange, install the flywheel with clean or new bolts and the thread locker and torque from SPEC's instructions, tightening in a cross pattern. Wipe the friction face with brake cleaner, center the disc with an alignment tool and torque the pressure plate evenly. A tired hydraulic system is worth replacing during the job; we carry the TJ master and slave cylinder and the YJ AX15 hydraulic set. Bleed with the fluid shown on the reservoir cap and follow the clutch maker's break-in.
| Brand | SPEC |
| Part number | SJ40S |
| Fits | Spec 92-96 Jeep Gr Cherokee 4.0L/90-06 CJ/DJ/Wrangler 4.0L Steel Flywheel |
| Vehicle fitment | Jeep Gr Cherokee 4.0L/90-06 Cj/Dj/Wrangler (1992-1996) |
| Type | Flywheels |
| Condition | New |
| Ships | Same business day (in stock), from the USA |
| Warranty | 1-year |
SPEC does not list any CJ or DJ model for SJ40S. Its fitment covers 4.0L Cherokee, Grand Cherokee, Comanche, Wagoneer and YJ/TJ Wrangler.
SPEC lists SJ40S for TJ and YJ Wrangler 4.0L from 1994 to 2006. Send us your VIN and we will confirm against your build before shipping.
No. SPEC lists the SJ40S at 25 lb in steel, a good fit for crawling and towing where flywheel mass helps.
SPEC's 4.0L Jeep kits run from the SD651 Stage 1 at 401 ft-lb to the SD655 Stage 5 at 768 ft-lb. Most trail Jeeps stay at Stage 1 or 2 for easy engagement.
Replace the pilot bearing and release bearing, check the rear main seal, and replace a leaking clutch master or slave cylinder while the transmission is out.
