TransTrem is a guitar vibrato system developed by Steinberger in 1984. Its main feature is to maintain the pitch of each string at the proper tuning interval to the others when the vibrato ("Whammy bar") is used. This allows entire chords to have their pitch bent while remaining in tune, whereas a conventional vibrato system would cause the strings to go out of tune with each other. The system also allows transposition of the pitch of the guitar as a whole: the pitch of all the strings can be raised or lowered from the standard EADGBE tuning and locked into one of several preset positions. The Washburn Wonderbar from the 1980s attempted a similar approach (sans the locking feature) with far less success.
The TransTrem (or TT for short) requires custom double ball end strings to work properly. Each string is calibrated to a specific length: as little as 1/16" deviation from this specification adversely affects string tuning. As of 2009 D'Addario, La Bella, GHS and the Steinberger brand strings are the only ones offering calibrated double ball sets.
In 1987, HAZ Labs, a company that provided the electronics for Steinberger (with the exception being the pickups, which were from EMG, Inc.), built roughly two-hundred TransTrem units for the bass. This mechanism did not gain much popularity and no further bass trems were ever built; however TransTrem equipped basses are now quite rare and valuable as collector's items.
In 2008 Steinberger introduced the third generation TransTrem (TT3) on the new Steinberger ZT3 guitar. It maintains the ability to tranpose all string in tune and lock in three other positions, while making setup and string changes easier. The new headpiece on this guitar also allows the use of single ball end strings. Lastly it moves the bridge mounted string tuners from a horizontal to a more upright position. This allows for a greater range of installations and/or body styles, as the tuner "cut out" on the tail end of the body is no longer necessary.