Sunday, April 21, 2013

6 speed Tremec Mid Shift Conversion



6 speed Tremec shifter relocation.

Billet mid shift or forward shift conversion.

I purchased my mid shift unit from performancepartswarehouse on ebay, in California,
They have various units available and the quality looks great.

So, this is the poor boys guide to fitting this kit, The correct installation method requires diss-assembly of the transmission using special tools and a high skill level.

My inspiration for this blog came about from searching for hours for a mid shift conversion and instructions on how to go about it.   Special thanks to Marovetsm and TR6 for thier contribution to the DIY handyman in us all.
The two forum articles I found that helped me out greatly, are...
(user name)  MAROVETSM  on  and  
(user name) TR6 on 
[touch the above names for direct link]

MAROVETSM did the simple method, partial pull down of the trans.
TR6 did his the Transmission shop method, complete tear down.
SPEED DEMON.  I did this without opening the trans case. 
This job took me 6 hours and I have a well equipped workshop,
I am fitting a 2005 LS1 with 6 speed Tremec into a 54 Chevy Truck
I need the shifter to be mounted on the floor, not between the seats.
In the picture below you can see the original extended shifter box on the far right of the tranny, and in the center top, the inspection port is where the new parts will be installed.

this opening is where the CAGS (skipshift), shift gate,and ball bearing detente are located. 
the CAGS solenoid will no longer be usable,
as the new part going in here does not have the
right shape and you will need to install a CAGS delete resistor (off ebay) on to the harness plug. 

First job was to drain the oil out, then remove the inspection cover, clean the inside with solvent, and stuff clean rag into all the cavities, then carefully mask off the interior, I put about 4 layers of tape.

Here we have it all sealed up and ready to make a mess, 
I have measured up the distance between the two roll pins used to secure the new shifter socket.
marked where the new top hole will go,
and using an air cutoff wheel I removed a small amount of the hardened surface in order for the drill bit to penetrate, 
the surface grinding turned out to be not enough, that hardening is deep.

I needed to work out a way to make a simple drilling jig up, 
so I could get the new hole in the right spot and straight.
I could have spent hours machining a custom block, 
but chose a simple method as many of you will have limited resources .
Started by machining a bit of rod to 15mm dia exactly,

Using the drill bit to center and align the shift socket roll pin hole in the Mill Drill, once the drill bit could go in and out without binding it was time to slide the jig shaft into place and make two holes. 

IF YOU GET THIS WRONG, your mistake will transfer to the shaft and your rooted. 
So take your time and get it PERFECT. 

Now check the fit and position, knock the lower pin in, and use a same size drill bit to locate the jig.

Now its time to remove the old selector.
Using a 1mm carbon cutting disc, cut in towards the shaft on both the left and right sides of the casting.
dont worry too much about marking the shaft, as most of the center section will be removed soon.

use a couple of alloy squares and clamp to align the two shafts. then drill the top hole.
Here we are ready to drill, it was slow going and when I got to the surface hardening on the other side I could go no further. and would need to grind the hardening on the other side of the shaft to complete the task.

alignment looks good so far, 
next job is to mark and cut the section out of the shaft. this bit is not easy to complete. 
you can just see the high and low lines marked on the shaft,

This part was a bitch, you will need a cutting disc with a diameter thats the same width as the cavity, and the skill and dexterity of a Ninja, 

 NOTE.. the grinding sparks will burn the masking tape.
once you cut the bottom, the upper part of the shaft can be rotated, (as long as you have punched the pin on the old shift socket)

Here is the old shift socket, at the far rear of the transmission, 

You will be keeping this in place as it activates the reverse lock out switch. (that little lump on the top right wall)
Dont freak out when you notice that this pin hole is not on the same center line as the holes you have drilled below. its all good. 

Here is the new shifter location all cleaned up and ready to go.
When you cut off the old casting, you will have noticed a spring loaded ball bearing, This ball rides in those little hollows on the lower section of this plate, the cut out above is the shift gate and limiter for the shifter travel.

UNFORTUNATELY I installed the new unit and found that it would not move, It seems that the distance from the shaft to the surface of the ball bearing hole, was different than the original cast unit. this caused it to jam on the ball indent surface. (you can see the scuffing on each side of the hole) I linished this protrusion down to half its height, and beveled those damaged edges some more.

here they are side by side

Thats it all installed, greased up the socket hole, 
last job is too fit the shifter, and you can use the Allen bolts (socket head) from the rear shifter location, and use the inspection cover bolts to secure the block off plate you need to make next. I used some 5mm alloy plate to make a new block off cover for the original shifter hole.

the new shifter has two little problems, 
the two small bolts just above the shifter boot protrude through too far, they stick out past the mounting surface and may hit the trans case casting, so grind them back some.
ALSO the lower mounting holes are slotted, the relief cutout on the  underside of the shifter plate leaves only a mm of contact area for gasket sealing, as there is no gasket provided. so I decided to make one from very thin aluminum, copper or gasket paper would also do. My gasket has a hole just big enough for the shifter boot an mounting bolts to clear. I sprayed the gaskets with copper coat sealer. and fitted washers to the bolts.