Boom Chains - JLG sky trak mmv Service Manual

Boom
4.3.6

Boom Chains

This vehicle uses double extend chains to extend the
boom and a single retract chain to retract the boom. The
extend and retract chains are constructed of 3/4" pitch
links with 6 x 6 leaf lacing.
IMPORTANT: DO NOT attempt to service or repair a
chain. Replace a stretched or damaged chain with a new
part. When replacing a chain, also replace both clevis'
and chain-to-clevis attaching pins with new parts.
a. Boom Chain Tension Check
1 000
MS21902
1. Park the vehicle on level ground. Place the travel
select lever in the [N] NEUTRAL position, place the
neutral lock lever in the [N] NEUTRAL LOCK position,
engage the parking brake switch and raise the boom
to a horizontal (level) position.
2. Fully extend the boom, then retract it 2" (51 mm)
(one inch per section). Shut the engine OFF.
3. Measure the sag (1) in the top extend chains
between the bottom of the chains and the top of the
intermediate boom (2) at their closest point.
Acceptable boom chain sag is between 1.5-2.5"
(38-64 mm). If the measurement is less than 1.5"
(38 mm), the boom chains may need to be adjusted.
Before making any adjustment to the extend chains,
check the following measurement at the rear of the
boom.
4.26
MT1750
4. Start the engine, retract the boom completely and
turn the vehicle OFF.
5. Go to the rear of the vehicle, open the rear door.
6. Check the measurement (3) from the rear of the
intermediate boom to the rear of the inner boom.
This measurement should be in range of 8.5-9"
(216-229 mm).
Note: If the intermediate boom to inner boom measure-
ment is less than 8.5" (216 mm); the boom may require
extensive adjustment and/or repair. Contact the JLG Ser-
vice Department or the nearest JLG Authorized Service
Center (ASC).
1
Model MMV Rev. 12/04
2
OA0491