• Hey Guest!
    British Car Forum has been supporting enthusiasts for over 25 years by providing a great place to share our love for British cars. You can support our efforts by upgrading your membership for less than the dues of most car clubs. There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Upgraded members don't see this banner, nor will you see the Google ads that appear on the site.)
Tips
Tips

TR2/3/3A Rebuilding A type OD I Need advise / measurements

Share this page

JFeher

JFeher

Senior Member
Offline
I've been collecting all the bits to complete the rebuild of my A type overdrive. I've completed installing the annulus and bearings in the rear housing and have good end float. I have the annulus thrustwasher and planet gears in place. I have the Moss# 866-560 thrust washer between the planet gear housing and sunwheel. After placing the thrust washer and spacer on the sunwheel I put the main housing on and installed the main shaft. The sun wheel end float should be .014-.020. I have .2. I think have every washer and bushing called for installed. I have read that to install the thrust washer in the planet gear housing requires the removal of one of the planet gears. I was able to slide the 866-560 thrust washer into place with out doing that. It's just a flat brass bushing with a taper on the side that faces the sun wheel. I can't figure out why I have such a gap. It does seem like the sun wheel is too low in the planet gear housing in how it fits within the planet gears. Does anyone have measurements of these items or have an idea of what I may be missing? It's a 22 61985 unit.

Thanks,
John
 
I have not measured, but the thrust washer inside the planet set is in the neighborhood of .2" thick. I see no way you could slide the old out or new in without removing a planet gear. Do you have a picture?
 
The bushing I got from Moss #76 in the Moss diagram part# 866-560 (to the left of the sun wheel) is only.0093 I think that may be the problem. Look how deepthe sun wheel sits in the planet gear housing.
attachment.php
attachment.php
 

Attachments

  • Planet_Sun.jpg
    Planet_Sun.jpg
    68 KB · Views: 252
  • Sun and washers.jpg
    Sun and washers.jpg
    63.5 KB · Views: 255
Is there any chance you have mis-matched parts? ISTR reading that the 28% gear set will allow that washer to be replaced without removing a planet gear (because the lower gears are smaller).
On my 22% set, there is no way it could be done.

Also, on my A-type that was severely over-pressurised, the case is apparently stretched. I had to add more than one adjustment washer to get the correct gap.

Worth noting, perhaps, that the spec for sun wheel end float was later reduced to .008" - .014". I suspect it may be advantageous to set the earlier units to that range as well.
 
The OD was a basket case (exploded) with a lot of missing pieces. I replaced the planet gears and housing and they match up with the old one. I have never seen a complete assembly so I'm going by all the references I can find, Buckeye Triumph, the manual and parts catalogs. Th planet gears that fit inside the annulus are smaller than the gears driven by the sun wheel.
 
That is normal for the 2 sizes of gears. Your sun is definitely sitting too low, but I cannot remember the shims that control that, other than the one captured inside the planet case. You can see in my one picture the 2 washer bushings that go on top of the sun gear. Those are the ones that control the amount of sun gear float. But still, your sun is sitting too low. The gears must have full contact across their faces.

I assume you are using the original sun with the replacement planet set? I wonder if they could be mis-matched?
 
A remote possibility to check - I believe Wishbone Classics machines the planetary gear housing to accept a thicker thrust washer. If by chance your housing has been machined the stock thrust washer would sit low which would make the sungear sit low too. That also might explain how you can get a thrust washer in there, in stock configuration I agree with Randall, I don't think the washer can be fit because of interference with the planetary gears.
 
The 28 % version will definitely allow the thrust washer to be replaced with no interference issue as Randall mentioned. I put one in my last rebuild - the washer is different from what you have as it doesn't have the outside bevel, but I don't recall it being thicker so I'm not sure what is causing your excessive clearance issue.
 
TR4nut said:
I put one in my last rebuild - the washer is different from what you have as it doesn't have the outside bevel,
Click to expand...
JIC it's not obvious, the 28% gears don't need the bevel, as the bevel is to provide clearance to the larger 22% gears. The difference in gear sizes is what gives the OD gear ratio.

When you shift into direct drive under power, the splines bind to some extent, and the motion of the clutch disc slams the sun gear into that thrust washer. With a tight clearance, the sun gear doesn't move very much and the impact is minimal. A larger clearance allows more of an impact. Hence, I believe, the reduced clearance specification, to reduce breakage of that thrust washer. But a thicker washer would certainly help too (as would reducing or eliminating the oil grooves). I intend to try that if mine breaks again.
 
Back
Top