Eeeeking differential .042" forward (working solo, tricks?)

[Lilleyvanilli]

Read a lot of great drive line related info this morning here, but still have a question and wanted to share some process.  Can anyone tell me HOW they've moved their differential forwards or backwards (what tools, where you wedged them, etc).  I've got all six nuts loose on the diff & cover (and center support), cleaned off as much crud as I can see/feel, but can't get the dern thing to budge.  Currently, the diff. is not being supported by a jack, thinking maybe could be binding?  Need to buy a bottle jack, then slide?  screw drivers? wood block & hammer?  Where to position/cram?

 

The photo shows where I sprayed a little paint with a pop sickle stick in place to show a reference line.  .042" is about 2/3 of the stick thickness and derived from analyzing my old guibo (5 spd/6bolt).  It took a set (complete with cracks) of .042" difference in height from one hole to the next (as in, when set guibo on a flat surface, every other hole was NOT sitting flat, but raised .042" measured with calipers).  With the new guibo in place, I thought my logic was sound to just bump the diff. forward a tad and that would bring the driveshaft flange .042" closer to the trans. output flange (and solve years of "guibo wars").  If I bump it too much, I'll warp the guibo in the opposite direction (thus my paint & pop sickle stick trick, as I can't just muscle the thing into place and I'm working solo).  Thinking now I should have just left well enough alone.  What's the best way to gently eeeek this baby forward into alignment? 

[TobyB]

Take the nuts off the bottom, and look at the oval holes in the subframe.

 

I have found that the front and rear slots don't always agree, as in, you

may have slide left in the front holes, but the rears are slid all the way forward.

 

Otherwise, it just takes some wiggling of the diff.  If the rear support is still

attached, it's not going to fall out or anything...

 

Good luck,

 

t

[Lilleyvanilli]

Ah, I purposely left the nuts on (fearing the diff tipping off the back), but yes the rear support is in place (cover bolts are loosened), plus the drive shaft is fully installed/torqued, so there's that holding it in too.  Thanks Toby.  Am I nuts for even bothering to move this thing this little an amount?

 

I have been wedging a large screw driver (and a pry bar that keeps slipping and is too long) between output shaft collars and a stout side cast part of the diff. casing on both sides of the diff. and jiggling it about without much luck.  I have a second long screw driver today.  They seem to wedge in there nicely.  Maybe now I should push upwards to "lift" the diff and somehow shove forward, once the nuts are removed?  I'm hoping with the drive line all buttoned up (except center bearing), I'll feel a little resistance from the guibo so I don't shove too far.

[JerryC]

Can you move the diff backwards at all? If you can, it's probably being stopped from going forward by the slotted holes.

Maybe you can get some of your .042" by loosening the engine and trans mounts and pushing the engine and trans rearward.

[Lilleyvanilli]

I'll see if I can pull it backwards, although with the rest of the drive line in place & tight (center bearing excluded), i'm a bit hesitant.  With the diff. nuts very loose (but not fully removed), I don't seem to be moving it at all using pry-screwdrivers.  If I am at my frontal limit, I'll def. be able to see once I remove the nuts.  So when moving this hulk, are folks just grabbing it with their hands?

 

New tranny mounts (I have 2, not one.  Don't ask.  It's one of those 5 spd. conversions) and what I think is a decent engine alignment.  Hope I don't have to go there (realigning eng/trans).  Never really had any vibration issues, just guibo jobs every 3 yrs.  See what being a perfectionist gets me?

[Buckeye]

I followed below procedure from Service Book and has worked very well.

 

 

[TobyB]

Yup, if you are losing guibos, it's worth doing.

 

And if this is a conversion, you might have a driveshaft that's too short.

I have one that's too long...

 

t

[andyleonard]

5 hours ago, Buckeye said:

 

 

 

 

Dunno what year you're working on, but this illustration/instruction is for a longneck 1600...which has a slipjoint in the driveshaft.,,making your situation impossible. 

 

I'm guessing the bedding system is the same for the newer cars but maybe with a solid driveshaft it's fussier.

 

We used to run the car in gear on the lift and let everything jiggle into place when the diff had been out. Then shut it down, preload the CSB and tighten everything in back.

[Lorin]

1 hour ago, andyleonard said:

 

Dunno what year you're working on, but this illustration/instruction is for a longneck 1600...which has a slipjoint in the driveshaft.,,making your situation impossible. 

 

 

That is not necessarily true, my 1600 has no slip joint or any u joints for that matter.

[Schnellvintage]

I have loosened the nuts and bolts for the engine mounts, differential mounts, trans mount and tighten the driveshaft bolts first. Then align the engine and trans and tighten that hardware. And finally tighten the diff hardware last. There should be enough total movement. To make it work, unless the driveshaft was cut too short...
Just my $.02 worth.
Matt


Sent from my iPhone using Tapatalk

[Buckeye]

2 hours ago, andyleonard said:

 

Dunno what year you're working on, but this illustration/instruction is for a longneck 1600...which has a slipjoint in the driveshaft.,,making your situation impossible. 

Not necessarily true.  I have short version diff and followed the procedure and has worked just fine. The illustration and procedure is from Service book. Do you have or know of similar instruction in BMW documentation that can share here for short version diff?

[andyleonard]

1 hour ago, Lorin said:

 

That is not necessarily true, my 1600 has no slip joint or any u joints for that matter.

 

If your 1600 has a longneck diff and a 3-rag joint-driveshaft like the one we're discussing in the diagram, then someone has stolen your slip joint.