Guitar Reviews 4U - Gretsch 5420T Machine Heads upgrade
The Wilkinson WJ45 Machine Heads - I use the Chrome ones in this upgrade
I had been considering doing this upgrade on my 2016 Korean made 5420T for some time to replace the original units for improved tuning stability, its a straightforward job to do.
I chose these units as they will fit the existing bushings and are 2 screw fixing - although I had to drill new holes. They also are based on the Kluson style units from the 1950's so look the job.
A shame that Gretsch didn't use the the sealed units from the modern Streamliner 2420 guitars on the Electromatic as they are much better.
I had a set of Wilkinson WJ45 3 + 3 units to go on the guitar in my spare parts stock. They are also 2 screw fixing type and based on a Kluson style design with a better gear ratio than the ones on the guitar at present.
Remember to check any screw sizes before drilling!
I am re-using the original screws that were on the guitar.
Later guitars may have different sized screws.
Always check the size twice before drilling!
The original unit left and the Wilkinson at right
Notice a moulded on collar on the original, more on that later!
Firstly, before removing a machine head unit I placed a small piece of masking tape under the machine head base lower side to ensure I had a straight line to work to after removing the original one. The original small holes for the baseplate do not match the hole spaces on the new WJ45 units so the old ones would have to be filled.
I used a PZ1 Screwdriver to remove the screws and it fitted the ones on the guitar fine. (Take care here removing the screws and ensure your screwdriver really fits well as the last pack of WJ45's I got for another job didn't have any new screws or bushings in and small screw heads are easy to damage.) If you rip the screw head recess this creates a real headache to get the screw out!
The Bushings for the Head stock were the same size as the new ones so I did not remove the old ones as the WJ45 posts fitted them fine, I did lube them carefully where the post touched the collar area.
I used cut down cocktail sticks to make filler plugs for the old holes that had to be filled as they did not line up to the holes on the baseplate of the new units. To do this cut off the sharpest part of a cocktail stick point at 3mm or 1/8" from the tip so there is still some taper on it, then using the original screw depth of 9mm, measure on and cut a c. 9mm filler plug from the stick to that length. This means you likely won't have any excess to trim off.
I used a small amount of PVA resin Wood Glue to glue the plugs in and this worked well - don't overpack the hole with glue as it may stop a tight fitting plug going in fully. I ensured the plugs were to the level of the headstock rear face by using the flat end of my scalpel blade holder to seat them flush.
One of the old screw holes is covered over by the new machine head under the plate on each new unit, but I decided to fill both old holes for each unit to make a good job of it. Once the new WJ45 machines are in place and the glue has had a day to dry out, I can paint match the exposed plugs.
Masking tape strip to help line up the new unit
I've done the E and A string units here.
I greased the new units before installing through the oil hole on the
back cover. I used a light duty general auto chassis grease from a tube
Having taken off the A string machine head I found that an order of removal would be needed here. When I test fitted a new WJ45 unit onto the headstock in to the A string position, I found that the WJ45 plate just sat on the E string baseplate of the old unit.
So I would have to also take the low E string unit off to get the clearance for fitting the new A unit, having firstly used a piece of marker tape placed for alignment purposes, before removing the old unit as you can see in the picture above. I found this method gave a clear run to the job and replaced the Low E and A string units together.
The original unit has a moulded collar to the baseplate -
I will use a lathe to hold the string post and cut these collars off with a parting tool
and at the next string change, then install them with the WJ45 units
to give more support to the base of the post into the headstock
For the new screw holes, I used a 1.5mm drill with a piece of masking tape 9mm from the tip as my drill depth gauge - you don't want to drill through the headstock plate here! I drilled one hole, blew out any wood debris and partly screwed in one screw to the new unit, I lined up the baseplate snug against my tape line, checked that the post wasn't binding in the bush by giving the key a turn or two and then drilled the second hole using the baseplate to the tape as a guide.
Once the second hole was drilled and any debris removed from the hole, I took the unit out and gave the post shaft at the lower end a light coat of Brass instrument Key oil to help lube it where it contacted the bushing and then lubed the small screws with beeswax.
I installed the WJ45 unit and screwed it down checking again that there was no binding of the bushing against the post. Then it was a case of doing the D string one and with that done, the top row of the units was completed. I was co-ordinating this upgrade with a string change so I didn't waste any strings in the job.
The rest of the high E, B and G string units were replaced in the same fashion and holes filled.
The new WJ45 keys look in place here from the front and suit the headstock size
The button style of these is like the G6118 Anniversary style ones
So, that's the job done, and the guitar has some improved machine heads on. I will likely remove the cast on collar bushings off the old units and next time I do a string change put those in the headstock holes to give the string post a bit more rigidity and support.
I did consider fitting locking machine heads to this guitar but I think these Wilkinson ones will be adequate. Once I have the colour match on the wooden plugs, it will finish the job off.
The Wilkinson units are around £25 GBP a set and although inexpensive look and feel good in operation.
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