Help - crankshaft end play too loose without shims

53a1 · Post by **53a1** » Wed Dec 23, 2009 9:15 pm

What do I need to do if it's not it in spec without any shims? The manual says .004 to .006 and I'm getting .008-.010 without shims so I can't get it any tighter. Does this mean I need new bearings? I would like to just run it as is.

Post by **wesk** » Wed Dec 23, 2009 10:55 pm

I don't understand why you do not want to follow the manual and install the necessary shims? The greater clearance you now have allows more travel which translates into accelerated wear each time thrust and clutch operation sends the crank forward and rearward. We assume if you are checking crank end play you are in the assembly phase of an engine rebuild and it only makes good sense at this point to set clearances correctly.

53a1 · Post by **53a1** » Wed Dec 23, 2009 11:43 pm

Wes,

If I add shims it increases the clearance, correct? The manual says if you need to increase clearance add the shims between the thrust washer and front bearing.

So if I'm at .010 currently with no shims how can I remove shims (per the manual) to get it to .004-.006? I don't think I can so I was wondering what now? Do I need new bearings?

I picked up a f134 engine and I had to change the front engine mount plate so I thought I would go through and check the end play while I'm at it.

Thanks.

Post by **wesk** » Thu Dec 24, 2009 8:34 am

If you are reading TM 9-8015-1 then I see why you are confused. Read it more closely. When it suggested you remove a shim it stated as an example if you are at .004 then remove the shim to open the clearance up to .006.

You ADD shims to decrease clearance and REMOVE shims to increase clearance.

53a1 · Post by **53a1** » Thu Dec 24, 2009 8:57 am

Thanks Wes and yes I am confused. I know what the manual says but by adding shims I'm increasing the gap between the thrust washer and front bearing and that gap is the slop in the end play. I must be overlooking something very simple.

53a1 · Post by **53a1** » Thu Dec 24, 2009 9:18 am

I went out to look at it again this morning and it makes sense now. The book is correct if the end of the crank doesn't extend past the front bearing. On mine, the face of the bearing is worn and the end of the crank sticks out past the front bearing so adding shims creates more end play.

Thanks Wes.

Post by **wesk** » Thu Dec 24, 2009 5:42 pm

The thrust washer's main job is to absorb the thrust motion of the crank. When the washer becomes inadequate in this task we add shims. Adding shims reduces the crank's forward/aft movement. We are not interested in holding the crank just forward or just aft. We want to limit it's total forward/aft travel. Adding shims limits travel and removing shims increases travel. So try to grasp this principal and just add 2 shims and your crank's end play (Forward/Aft Travel) will be reduced about 2 or 3 thousandths from .010 to about .070 or .060.

BullRun · Post by **BullRun** » Thu Dec 24, 2009 6:05 pm

I checked my engine rebuilding reference books and they state end play should be between .004 to .010 unless specified. In this case there is a specification of .004 to .006 apparently due to a design reason.

If not to this specification the engine is rebuilt incorrectly.

The reason it is important is because as the connecting rods rotate in the engine block, if there is to much endplay, it can cause the angles on the connecting rods to become extreme enough to allow the ends of the rods to hit internal metal projections (for lack of a better term) along the bottoms of the cylinder walls causing a potentially engine destroying impact. This is the explanation from my engine books.

According to the TM's proper rebuild procedure is to use shims to correctly adjust end play. If no shims are used it is not correct. Something is also wrong in the parts or how it was assembled if under .004 thickness of shims or if more than .006 thickness of shims is needed.

According to my engine books there are several factors that can effect endplay adjustment preventing a correct measurement.

1) The end face of the crankshaft could have surface damage preventing proper spacing. Serious.

2) The bearings could be slightly out of measurement as in too wide or thick. Apparently common to replacement (ie: not NOS) bearings and not a big deal, see below.

3) The bearing may not be sitting straight or parallel to the face on the crankshaft. Minor

To fix #1 the crank may need to be spray metal surfaced and turned down by an engine machine shop or a new crank sourced.

To fix #2 the bearings surface needs to be carefully hand wet sanded on a surface plate with 600 grit wetsand sand paper.

To fix #3 get machinist dye and coat the surfaces, reassemble, rotate the crank a few times, disassemble and inspect the dyed bearing surfaces for even wear or uneven wear surfaces. Adjust if necessary.

I would get an engine "blueprinting" book as a general guide that shows how to do these things and use it in conjunction with the TM's.

Wes, is right, apparently with this type of engine, crankshaft end play is a critical measurement that was important enough for proper performance, that the designers had to specify a specific range of measurement to it.

The time taken to do this right will pay back with years and years of trouble free service (hopefully). It is hard to kill these engines but apparently not having proper crankshaft endplay is a way to do it.

I hope this helps your project.

53a1 · Post by **53a1** » Sat Dec 26, 2009 8:20 am

Thanks for all the help. I added shims and just as I thought it increased the end play. I even double checked it with a dial indicator and it increased the exact amount as the added shims. It's at .007 total end play using the dial indicator without shims and just as bullrun said I think the bearing is out of spec. I'll continue going through the engine to check things out.