Monster MST9112 Swivel Extension Set Review

Monster MST9112 Swivel Extension Set Featured Image
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Final Thoughts

Quit cobbling together extensions to haphazardly do your work. Get the Monster MST9112 swivel extension set that comes in a complete kit.

User Review
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We all dread either crawling under a vehicle or going under the lift to remove those hard to reach fasteners. In particular, transmission bellhousing bolts. The Monster MST9112 swivel extension set eases the frustration of removing said fasteners. No more cobbling together all your extensions and that flimsy universal. These built-in extension and universal sockets are 17 inches in total length.

It’s not just transmission bolts that this 3/8” extension kit will help with, as we’re sure every technician out there has something in mind at this moment. This set doesn’t even require a ratchet, hence it comes with a T-handle for quick use. Also, the handy blow-molded case enables safe and convenient travel.

While this Monster MST9112 universal set is not impact rated, they also have the Monster Impact Swivel Extension Sockets.

Monster MST9112 Swivel Extension Set Features


The Monster 3/8” MST9112 swivel extensions are made from chrome vanadium for strength and durability. In addition, the chrome finish makes for easy cleanup. Spline style sockets allow them to be used with most fasteners, not just 6 or 12-point. Large engraved markings make it easy to read the size of each socket, so you get it right the first time.

Monster MST9112 Chrome Vanadium

Monster Swivel ExtensionThe included T-handle is 8-inches in length to provide needed leverage. This T-handle includes a push-button detent on the end to allow the handle to be passed through the large hole in each extension. Once centered in the extension head, a spring-loaded ball in the extension head locks into a groove in the T-handle. Of course, the typical 3/8” ratchet can be used with these as well. This kit doesn’t include a ratchet, but the case does provide a place to store a 3/8” ratchet.

Each universal swivel in the Monster MST9112 set includes two Torx screws, instead of pins. We like this, so the user can tighten these joints, as they tend to get loosy-goosy over time. Pins would not allow you to do so. Out of the box, these joints hold their angle well, however still easy to move. This enables the user to reach the fastener with the socket, without the need to reach the fastener with a hand.

Testing and Projects

Monster MST9112 - Oil StainsIf there is such thing as a good time for a transmission leak, it was now. We have a project car here at STR headquarters, a 1971 Oldsmobile 442. After completing bodywork on the rear quarters, we moved the 442, only to find two (2) oil marks on the concrete. Ugh!! The red tint quickly told us tranny front seal, rather than rear main of the Olds rocket. Well, better now than after it’s finished.

We pulled out the Monster MST9112 swivel extension set to give them a test. The KTool International KTI63099 3 Ton Aluminum Jack also came in handy to get the 442 on jack stands. Using the included T-handle with the swivel extensions worked OK, although everyone agreed that using a standard 3/8″ ratchet was better and made more sense.

Monster MST9112 with Monster Ratchet

The lower two bolts on the either side of the Turbo-Hydro-400 were able to be removed with only the 17″ swivel extension. Add, of course, the T-handle or 3/8″ drive ratchet. For the upper bolts, we just added another 3/8″ x 12″ extension to make the process…a little more enjoyable. Impacts were not needed for this job, so the non-impact rated extensions are no issue. At the same time, it is good to know that Monster has an answer for this too. Monster’s swivel extensions have held up well during our testing, and we don’t have a problem recommending them.

Monster MST9112 Tranny Removal

Monster MST9112 Swivel Extension Set Specifications

  • Drive Size: 3/8 in.
  • Length: 17 in.
  • Included Sizes: 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, and 19mm. Also includes T-handle
  • Socket Design: Spline
  • SAE or Metric: Metric
  • Material: Chrome Vanadium
  • Warranty: Lifetime


Final Thoughts

Monster MST9112 with T-handleAnytime we come across tools that help technicians do their job better and faster, we’re a fan. Without a doubt, the Monster universal extension set does just this. With 17 inches from tip to tip, the Monster MST9112 swivel extension set makes easy work for reaching stubborn fasteners. The universal extensions performed very well for us in the testing we did here in the shop. This included removing the transmission bolts in our ’71 Olds 442 project car. Including 12 pieces, from 8mm to 19mm, without skipping any sizes, makes a nice and complete kit. The included lifetime warranty provides assurance of not having to purchase again. Technicians and mechanics will find many uses, in addition to transmissions, for this Monster kit.

Click the link to find out more information about the Monster MST9112 Universal Extension Set.

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