Well as I was waiting for the timing plate to come back from the platers I thought I'd get on with the gearbox.
First job was to re-thread the three 5/16 holes in the transfer case end of the casing. As mentioned earlier someone had bodged these with UNF bolts. One of the other UNC threads looked a bit dodgy so I decided to do all three.
Here is one of the dodgy threads.
I got everything ready and did a quick bit of revision on how to fit a helicoil (never done it before).
First job was to drill the holes, using the supplied 21/64 HSS Drill Bit, here is one part done:
The plastic and tape was to prevent crud and swarf getting into the nice clean casing.
However when I took the tap out it just looked too big and when presented to the hole, even the smaller tapered end would not fit.
Turns out they had sent a 3/8th STI Helicoil Tap instead of a 5/16 STI Helicoil one :-(
I contacted the company but as I did not get a quick response and as I wanted to avoid delay, I ordered a V-Coil set (recommended by John Guess as pretty good value), I also ordered some 2D 5/16 UNC coils as the ones supplied with the kit are only 1D. The 'D' number is the depth of the coil and relates to the diameter of the hole. 1D is only about 10mm so I though a 2D would allow for more of the bolt to be in contact with the threads.
The correct Tap arrived in the post on Saturday, along with another V-Coil set that I ordered and the 2D 5/16 x 18 UNC Coils.
As you can see the 2D coils are much longer:
To be honest I was a bit nervous as I'd never done this before and did not want to mess up the gearbox casing. I carefully threaded the hole ensuring that the Tap was perpendicular to the hole. Once done I inserted the coils.
I used a T handle, as I do not possess a standard Tap holder:
Hole Tapped:
Helicoil fitted:
Job done:
Still waiting for the 5/16 bolts to come back from the platers so I could not test them out. I also now need to order some additional 5/16 UNC bolts to replace the 5/16 UNF that came out.
Tomorrow I am hopefully going to start putting the gearbox together, but I think I am on Grandad duty
Edited by JonnyAlpha, 10 August 2020 - 07:14 PM.