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AW-4 Transmission Swap


With the t-case's input shaft at the correct length, the t-case was bolted to the end of the AW4 and that item on my checklist was marked as finished.  Now it was time to turn my attention to a tranny mount.


I followed ScottK's lead on doing this, although I am going to be changing the mount/bracket to one that sits a bit lower.  Jumping ahead just a bit (about two days), I found that I have just the slightest CV joint bind when my rear axle is at full droop.  My drive shaft length seems to be OK but the CV joint issue must be addressed.  Troy took a look and agreed that either the joint needs to be disassembled and a die grinder used to remove the offending metal....OR....redesign the mount to allow the tranny/t-case to fit closer to the skid.  The latter idea is the better of the two since it will eliminate the CV bind by reducing the operating angle.  At the same time, a reduced operating angle means longer CV joint life expectancy.  And lastly, my pinion angle, which is now too low, will not have to be increased nearly as much to align it to the CV drive shaft.  A lower pinion angle on the differential means better oiling of the pinion bearing.  So all in all, designing a lower mount is the best solution and will be worked on once the vehicle is rolling.  (note that I do not have a clearance issue at normal ride height, only when both rear tires are a full droop).

I will note that YOUR setup is probably not like mine.  The CV joint on the drive shaft, skid plate height (and brand), and coil spring height all come into play when working through this kind of an issue.  Just because I had an issue with it does not mean you will.  Just something to consider when you are doing your project planning.

Anyway, back to ScottK's mounting bracket.  I cut a 1/4" thick plate to a dimension of 6"x10".  Mark a line 2" from the front edge of the plate.  On that line, from the center line of the plate, mark a hole 3 3/8" towards the driver's side.  Also mark a hole 2 7/8" towards the passenger side.  These two holes are used to mount the plate to the tranny, as shown in the above photo.  If memory serves me correctly, I made the holes 1/2" diameter.

 

Now it was time to determine the placement of the stock tranny mount on the new plate.  To do this, I set the tranny mount on the skid plate (this properly positioned the mount in the existing mounting holes).  I then raised the skid plate up into position and put a few bolts in place to hold it.  I then slowly lowered the jack holding the tranny until it came to lightly rest on the skid plate.  In my case (ScottK also commented on this), a corner of the tranny mount hit the AW4 mounting bolt.  The above photo is taken from the rear of the skid plate (look towards the front of the vehicle) and I've outlined the area where the AW4 bolt is hitting the stock tranny mount.  The other side appeared to clear OK but it too was close.

When I new where the clearance problem was, I lowered the center skid and cut a small part of the tranny mount away. 

 

Once I had the tranny mount trimmed, I put it back in place and raised the center skid one more time to make sure there were no more clearance issues.  It looked good so I took a crayon (grease pencil) and traced the outline of the mount against the plate.  When I lowered the skid, I could then properly position the mount on the plate and mark the holes needed to bolt those two together. 

 

As ScottK mentioned in his write-up, one pair of the tranny mount bolt heads will interfere with the plate bolting flush against the bottom of the AW4.  I cut the heads off of a pair of Grade 5 bolts and Troy welded them into the plate for me.  The rear most pair of mounting bolts pose no problem so there is no reason to turn them into "mounting studs" like the other pair.  The above photo is the flip side of the mounting plate, the side that bolts up flush to the bottom of the AW4.
 

More AW-4 Tranny Swap

 

 

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