The Mahindra CJ340 rides on leaf springs at both ends, an arrangement inherited from the Willys CJ-3B and unchanged in principle since the 1940s. It is simple, immensely strong, entirely repairable by hand, and largely responsible for the CJ340's reputation for a firm ride. Nothing about it is sophisticated, which is exactly why it still works after thirty years of neglect.
What leaf springs do not do is fail suddenly. They sag slowly over decades, and because the change is gradual most owners never notice how far the vehicle has settled. A CJ340 sitting nose-down with the rear arches close to the tyres has usually lost its rear spring arch, and the consequences run well beyond appearance — steering geometry, brake balance under load, and driveshaft angles all shift with ride height.
How the suspension is put together
Semi-elliptic leaf springs locate the axles both vertically and longitudinally, which is the key point: on a leaf-sprung vehicle the springs are also the suspension links. There are no separate radius arms or trailing links to take drive and braking loads. Anything that lets a spring move — a worn bush, a stretched centre bolt, loose U-bolts — therefore changes axle location, not just ride quality.
Each spring is fixed at one end to a chassis hanger and at the other to a swinging shackle, which allows the spring to lengthen as it flattens under load. The shackle is the highest-wear point in the system and the first place to look for clonks.
A centre bolt through the spring pack locates the leaves relative to one another and locates the pack on the axle. U-bolts clamp the pack to the axle. If the centre bolt shears — not rare on a jeep that has worked — the axle shifts backwards or forwards on that side, and the vehicle will crab and steer oddly. It is worth checking specifically on any CJ340 that tracks strangely.
Dampers control oscillation only; they carry no vehicle weight. A CJ340 with dead dampers pitches and wallows but does not sit low. Conversely, new dampers do nothing whatsoever for a sagged spring, which is a common and expensive misunderstanding.
Diagnosing sag
Measure rather than judge by eye, because the settling is symmetrical enough to look normal. The practical measurement is from the axle tube up to a fixed point on the chassis, taken on both sides with the vehicle on level ground and unladen. Compare left to right first — a difference across an axle indicates one broken or tired spring and shows up as a vehicle that leans.
Comparing to factory ride height requires the figure from the workshop manual, which is worth obtaining before ordering springs. Absent that, photographs of known-original vehicles and the arch of the springs themselves are a reasonable guide: a spring pack that has gone flat or inverted has clearly lost its arch.
The consequences of sag are worth taking seriously on this vehicle. Reduced bump travel means the axle contacts the bump stops on ordinary bumps, which is both uncomfortable and hard on the chassis. Steering geometry changes as ride height drops. On the rear, a sagged spring alters the propshaft angle, which shortens universal joint life and can introduce vibration that gets misattributed to wheel balance.
A leaning CJ340 is not always the springs. Check for a broken main leaf, a sheared centre bolt, and collapsed body mounts before condemning the pack, since all three produce a lean and are cheaper to fix.
- Measure axle-to-chassis on both sides, unladen, on level ground
- A side-to-side difference means one broken or tired spring
- Both sides low means the pack has lost arch through age
- Check the centre bolt and U-bolts before buying springs
- Check body mounts — a collapsed mount mimics a sagged spring
Re-arching versus replacement
Two routes exist for tired springs, and the right choice depends more on your market than on the springs themselves.
Re-arching means heating and re-setting the existing leaves to restore the original curve. Any traditional spring works can do it, the price is usually modest, and it keeps the original components on the vehicle — relevant if you are preserving originality. The drawback is durability: a re-arched spring has already fatigued once and will generally settle again sooner than a new one, particularly if the vehicle works hard.
Replacement gives a known starting point and, on a CJ340, is often available because Mahindra springs remain in production for related models and because pattern parts exist. Where new Mahindra-specification springs are hard to find, a spring works can manufacture a pack to a sample or to measurements — this is routine work in the commercial vehicle trade and is how many owners in Europe and Australia solve the problem.
Adding leaves to stiffen a pack is a common bush fix and should be approached carefully. It raises the vehicle and increases load capacity, but it also stiffens the ride considerably and increases stress on mounts and chassis. On a jeep that already rides firmly, more leaves rarely improve anything except carrying capacity.
Whichever route you take, replace the U-bolts. They stretch in service, they are cheap, and a stretched U-bolt lets the pack move on the axle — which undoes the entire job.
Bushes and shackles
Shackle and spring-eye bushes are the highest-wear items and the usual source of clonking over bumps and vagueness in the steering. They are also among the cheapest parts on the vehicle, which makes them the sensible first job on any CJ340 that feels loose.
Diagnose with a lever. With the vehicle safely supported, lever between the spring eye and its hanger and watch for movement between the pin and the bush. Any visible play means the bush is finished. Check the shackle plates themselves for elongated holes, which is common on hard-worked vehicles and cannot be cured by fitting new bushes alone.
Rubber and polyurethane are both viable. Rubber is original in character, absorbs more noise and vibration, and lets the suspension articulate with less bind. Polyurethane lasts longer and holds location more precisely, at the cost of transmitting more noise into a vehicle that is already loud, and it requires periodic greasing to avoid squeaking. For a working CJ340 the extra harshness is rarely noticed; for one used on long road journeys, rubber is often the more comfortable choice.
Seized pins are the practical obstacle. Decades of corrosion frequently weld the pin to the bush sleeve, and heat plus a press is often the only route. Budget time for this rather than expecting a quick job, and buy new pins at the same time as bushes because removal frequently destroys them.
Setting up and living with it
Torque U-bolts evenly and in stages, working diagonally as you would wheel nuts, and re-torque them after the first few hundred kilometres — new springs settle and the clamp loosens. This single step prevents most repeat failures after a spring job. Confirm the correct figure in the workshop manual rather than guessing, since under-torqued U-bolts let the pack shift and over-torqued ones can crush the pack.
Grease the shackle pins if they have grease nipples, and add them if they do not. On a vehicle that works in mud and dust, regular greasing is the difference between bushes lasting years and lasting a season.
Expect a firm ride and do not try to engineer it away. The CJ340's suspension was designed for load carrying on poor surfaces with a short wheelbase, and the combination is inherently choppy on smooth tarmac. Correct spring arch, sound bushes and functioning dampers give you the ride the vehicle was designed to have — which is firm, controlled and entirely honest about the road surface.
Finally, check the chassis around the spring hangers whenever the suspension is apart. Hangers are welded to the chassis rails, they collect mud, and corrosion there is structural rather than cosmetic. It is far easier to inspect and treat with the springs out than to discover it during an inspection.
Frequently asked questions
How do I know if my CJ340 leaf springs are sagged?
Measure from the axle tube to a fixed point on the chassis, on both sides, unladen and on level ground. A difference between sides means one broken or tired spring. Both sides low means the packs have lost their arch. Check the centre bolt, U-bolts and body mounts before buying springs, because all three can mimic sag and are cheaper to fix.
Should I re-arch or replace CJ340 springs?
Re-arching is cheaper, keeps the original components and can be done by any traditional spring works, but the leaves have already fatigued once and will settle again sooner. Replacement gives a known starting point. Where Mahindra-specification springs are hard to source, a spring works can make a pack to your sample — routine work in the commercial vehicle trade. Replace the U-bolts either way.
Will new shock absorbers fix a saggy CJ340?
No. Dampers control oscillation but carry no vehicle weight, so they cannot affect ride height at all. A CJ340 with dead dampers wallows and pitches but sits at normal height; one with sagged springs sits low regardless of how new the dampers are. Diagnose the two separately.
Rubber or polyurethane bushes for a CJ340?
Rubber is original in character, quieter, and allows more articulation without bind. Polyurethane lasts longer and locates the axle more precisely but transmits more noise into an already loud vehicle and needs periodic greasing to stop it squeaking. For a working jeep the harshness goes unnoticed; for long road journeys rubber is usually more comfortable.
Keep yours on the road
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