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armchair engine builder
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Discussion Starter #1 (Edited)
Mainshaft thrust adjustment

I thought I'd make a little DIY to clarify some of the steps outlined in the helms manual for checking and setting the mainshaft thrust on a 6 speed k-series transmission.

DISCLAIMER

Use this guide at your own risk. I assume no liability for anything that happens to your vehicles as a result. Always make sure to check your work to verify accuracy.

Measurement 1

This is the measurement from the edge of the transmission case to the washer on the mainshaft




The Helms manual calls for the mainshaft to be disassembled and partially re-assembled during this process. It is to be stripped down to a bare mainshaft and re-assembled with the following components. It is important to note that the bearing on the mainshaft has a right and wrong direction of installation. See Helms manual for further explanation on mainshaft assembly.



The transmission case has a 72mm shim and oil guide plate at the bottom. These both need to be removed.



With the shim removed and the mainshaft prepared, install the mainshaft into the transmission case. Make sure it is fully seated. Again, use a straight edge and a caliper / depth gauge when measuring. Notice that the washer is not in place on the mainshaft. The helms manual calls for washer "h" to be installed when taking this measurement. I found that the washer actually put the surface of the mainshaft above the edge of the transmission case. I chose to remove the washer, take measurement from the edge of the transmission case to the surface of the mainshaft, then subtract the thickness of the washer "h" to determine how far it protrudes from the edge of the transmission case. Measure from three different locations and average the readings. This may result in a negative number (which is correct if the edge of the mainshaft is above the edge of the transmission case)

  • install mainshaft
  • make note if washer "h" will be installed during measurements
  • measure from edge of transmission case to mainshaft in three spots
  • average reading
  • perform calculations
edge of transmission case to mainshaft (without washer "h") - 1.45mm
Thickness of straight edge - 1.00mm
thickness of mainshaft washer "h" - 0.98mm

Measurement 1 = (1.45mm - 1.00mm) - 0.98mm = -0.53mm














Measurement 2

Measurement 2 is the distance from the edge of the clutch case to the inner race of the mainshaft bearing





Use a straight edge in conjunction with a caliper or depth gauge to take this measurement. Remove any silicone from the measuring surfaces. Don't forget to factor out the thickness of the straight edge from the observed measurement. Measure at three different points and average the readings.








Observed measurement is 4.00mm. Thickness of straight edge is 1.00mm.

Measurement 2 - 4.00mm - 1.00mm = 3.00mm




Calculations

Armed with measurements 1 & 2, calculations can be made to determine the proper 72mm shim thickness to use in the transmission case. Two formulas are given to determine the maximum shim thickness and minimum shim thickness. Armed with the minimum and maximum numbers, Honda recommends the shim that falls between the maximum and minimum.

measurement 1 + measurement 2 - (0.8 + 0.11) = maximum shim thickness
measurement 1 + measurement 2 - (0.8 + 0.17) = minimum shim thickness

-0.53 + 3.00 - (0.8 + 0.11) = 1.56
-0.53 + 3.00 - (0.8 + 0.17) = 1.50

In this case, the manual would call for a shim of 1.53mm.

Verification

Select and install the proper 72mm shim (along with the oil guide plate) according to your calculations. Install washer "h" and the spring washer (in the correct orientation) on the mainshaft. Assemble the mainshaft in the transmission case and assemble the transmission / clutch cases following the provided torque specifications.



Attach the mainshaft tool (available from your local honda dealer).




Tap the mainshaft down with a dead-blow hammer to make sure it is fully seated. The mainshaft tool is used to pull the mainshaft up so the user can measure thrust. With the mainshaft fully seated, zero a dial indicator on the end of the mainshaft. Make sure the bolt on the mainshaft tool has something to press against. Honda sells a special adaptor that goes around the mainshaft output, but i used an old piece of steel i had laying around.






with the dial indicator zeroed, turn the bolt on the mainshaft tool until the needle n the dial gauge stops moving. Do not turn the bolt more than 60 degrees after the needle of the gauge stops moving. Applying more pressure may damage the transmission. If the reading is within the standard, the clearance is correct. If it is not, recheck the shim thickness.

Standard 0.11mm - 0.17mm (0.004 - 0.007 in)

Troubleshooting

Here are some things to check if the numbers aren't adding up

  • Make sure bearing is fully seated in clutch case
  • Synchro hubs / bearing are fully seated on mainshaft
  • Excessive amounts of silicone left on transmission / clutch case
  • Errors in math / formulas / calculations
Excel Spreadsheet
drkangel348 helped me out in compiling what I hope to be a useful spreadsheet. It is setup to do the math for you to figure out which shims are recommended by the helms service manual. All you have to do is input the two measurements and it will spit out the shim size and the honda part number. Keep in mind this is merely going by the method described in the manual. If you want to shim it tighter/looser than it is your choice and you should not follow the data produced by the excel spreadsheet.

Excel Spreadsheet

Final Thoughts

I'm sure i've skimmed over some steps while writing this. If there is anything that is not clear or that i've missed please let me know. I Hope someone can use this at some point. I'll be making revisions / clarifications as needed.

:funny:
 

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:ugh: I wish this task was within my capabilities. Props to you and anybody who would tackle this. I suppose if I had all the proper tools at my disposal, this would be a little more feasible. :thumbsup:I'm jealous
 

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Bay Area
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OMG WHERE WERE YOU when I did my transmission rebuilt!!. hah I wish I had this guide because it was a bitch trying to decrypt the damn manual. Thanks dude, your the best!..
 

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armchair engine builder
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Discussion Starter #7
Thanks for the comments. i'll probably do another diy for something else in the transmission when i have more customers coming through.
 

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how can you tell if the mainshaft is completely seated in the trans housing? does the mainshaft need to be disassembled and partially reassembled for to get the proper measurements?

i didnt disassemble the mainshaft and im getting 1) 8.2mm at the transe case and at the clutch case im getting 2) 3.7mm
 

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Been there & gone back
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I know I should not bump an old thread but this info IMHO is very important and honestly should be a sticky as it is required to rebuild a trans properly. Now that the RSX is getting to be an older car I would suspect more people will be looking for information on rebuilding the trans and doing it the right way. I am in the process of rebuilding mine to freshen things up and get some TSX gears in and do appreciate the good information here as part of the process.

In addition we are trying to get twat over on the supercharger side to rebuild one. :) If you know him he has lots of questions so all the help we can get is good. he he he.........

Thanks Bigworm85 for fixing the image links.
 

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Meth Blow Speed = my life
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7,078 Posts
I know I should not bump an old thread but this info IMHO is very important and honestly should be a sticky as it is required to rebuild a trans properly. Now that the RSX is getting to be an older car I would suspect more people will be looking for information on rebuilding the trans and doing it the right way. I am in the process of rebuilding mine to freshen things up and get some TSX gears in and do appreciate the good information here as part of the process.

In addition we are trying to get twat over on the supercharger side to rebuild one. :) If you know him he has lots of questions so all the help we can get is good. he he he.........

Thanks Bigworm85 for fixing the image links.
Here I am!!

My main question is why would you want to adjust the thrust of the mainshaft? Just curious why you would go through this hassle. Is this mainly just to ensure that everything is put together properly?
 

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armchair engine builder
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2,484 Posts
Discussion Starter #12
Here I am!!

My main question is why would you want to adjust the thrust of the mainshaft? Just curious why you would go through this hassle. Is this mainly just to ensure that everything is put together properly?
it's not something that one would adjust for the sake of doing so. This process of measurement and adjustment is performed when you're switching out a component that would change the thrust clearance. Replacement of the mainshaft, bearings, or either half of the transmission case would warrant at least checking the mainshaft thrust.

this is just one of the measurements that honda specifies when rebuilding the k-series trans.
 

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Meth Blow Speed = my life
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7,078 Posts
it's not something that one would adjust for the sake of doing so. This process of measurement and adjustment is performed when you're switching out a component that would change the thrust clearance. Replacement of the mainshaft, bearings, or either half of the transmission case would warrant at least checking the mainshaft thrust.

this is just one of the measurements that honda specifies when rebuilding the k-series trans.
Thanks BigWorm. This is definitely something I'll suscribe to so I can reference it in the future.
 

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Been there & gone back
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Thanks BigWorm. This is definitely something I'll suscribe to so I can reference it in the future.
In the chat I uploaded a pdf version for you as well Sam. I needed this because I am doing a complete teardown and rebuild as Bigworm was saying. If its not in spec bad things can translate from it such as premature wear or worse.
 

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Dafkup
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it's not something that one would adjust for the sake of doing so. This process of measurement and adjustment is performed when you're switching out a component that would change the thrust clearance. Replacement of the mainshaft, bearings, or either half of the transmission case would warrant at least checking the mainshaft thrust.

this is just one of the measurements that honda specifies when rebuilding the k-series trans.
Cant believe I never saw this. I have the same tool 'Mainshaft Holder' courtesy of you actually and Honda of course lol. I also have the base though that you screw the holder against. This ranks with the best and most professional write ups I've seen out there.:thumbsup: Thanks again
 

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Excellent!

This needs to be made a sticky!

I have all the necessary tools / measurement devices to do this but the Helms proceedure does make it rather needlessly cryptic. Thank you for posting this! I'm about to do a complete re-build on my transmission (new bearings, seals, sychros and of course, the infamous 2nd gear). This post will be invaluable.:thumbsup:
 

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armchair engine builder
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2,484 Posts
Discussion Starter #20
Are the measurements and standards the same if I were to add Quaife LSD, 5.06 FD, and TSX 6th?
The measurements that this thread address (mainshaft thrust) shouldn't be changed by those parts. The only thing you'll have to watch out for is the thrust clearance you have with the new differential. If the thrust clearance isn't checked with the quaife, it possible that you could have too thick of a shim causing some distortion in the back half of the case when it's closed.
 
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