Th400 rear planetary pinions.

Mr. Breeze

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I have a 400 I'm rebuilding that one of the 4 helical pinions in the rear planet is getting hung up "hard to turn". Looks like it may have gotten hot at some point, has some discoloration and bluing on surrounding metal.

Question is, anyone ever successfully rebuilt their own planets here?

I thought there was a kit available years ago that you could buy to rebuild these that came with all the needle bearings/pins/washers and shit.

Worth doing or just buy another rear planet? Looks like you'd have to drill/grind the pins to get the pinions out, not sure how you re-crimp the new hardware either?

Just buy new/used planet set and quit being cheep ass?

Curious if anyone's ever redone them before?
 

Tom396

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Dug out my old 1969 Chevrolet "Chassis Overhaul Manual", not to be confused with the mere Chassis Service Manual. :giggle: They make it sound easy (don't all overhaul/service manuals?). The illustrations absolutely suck, so it isn't as if you are really missing much.

Here we go.

1. Support carrier assembly on it's front face. (There is no illustration of which is the front face, so I assume that means the face that points forward during assembly).

2. Using a 1/2 inch drill bit (probably best in a drill press, but it doesn't say that), remove stake marks from the end of the pinion pin, or pins, to be replaced. This will reduce the probability of cracking the carrier when the pinion pins are pressed out.

Caution: Do not allow drill to remove any stock from the carrier.

3. Using a tapered punch, drive or press pinion pins out of carrier.

4. Remove pinions, thrust washers and roller needle bearings.

5. Inspect pinion pocket thrust faces for burrs and remove if present.

6. Install eighteen needle bearings into each pinion using petrolatum ( I guess that is what they called petroleum grease) to hold bearings in place. Use pinion pin as guide.

7. Place a bronze and steel washer on each side of pinion so steel washer is against pinion, hold them in place with petrolatum.

8. Place pinion assembly in position in carrier and install a pilot shaft through (I guess they mean the pinion pin? There is no illustration) rear face of assembly to hold parts in place.

9. Drive a new pinion pin into place while rotating pinion from the front, being sure that headed end is flush or below face of carrier.

10. Place a large punch in a bench vise to be used as an anvil while staking opposite end of pinion pin in three places (again, no illustration).

Note: Both ends of pinion pins must lie below face of carrier or inference may occur.


Not in this section, but in the "inspection" section, it says that the pinion end play should be .009"-.024" (be nice if they suggested a cure if it isn't). The illustration shows using a feeler gauge to measure the end play.

Take care. Tom Worthington
 

Mr. Breeze

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Dug out my old 1969 Chevrolet "Chassis Overhaul Manual", not to be confused with the mere Chassis Service Manual. :giggle: They make it sound easy (don't all overhaul/service manuals?). The illustrations absolutely suck, so it isn't as if you are really missing much.

Here we go.

1. Support carrier assembly on it's front face. (There is no illustration of which is the front face, so I assume that means the face that points forward during assembly).

2. Using a 1/2 inch drill bit (probably best in a drill press, but it doesn't say that), remove stake marks from the end of the pinion pin, or pins, to be replaced. This will reduce the probability of cracking the carrier when the pinion pins are pressed out.

Caution: Do not allow drill to remove any stock from the carrier.

3. Using a tapered punch, drive or press pinion pins out of carrier.

4. Remove pinions, thrust washers and roller needle bearings.

5. Inspect pinion pocket thrust faces for burrs and remove if present.

6. Install eighteen needle bearings into each pinion using petrolatum ( I guess that is what they called petroleum grease) to hold bearings in place. Use pinion pin as guide.

7. Place a bronze and steel washer on each side of pinion so steel washer is against pinion, hold them in place with petrolatum.

8. Place pinion assembly in position in carrier and install a pilot shaft through (I guess they mean the pinion pin? There is no illustration) rear face of assembly to hold parts in place.

9. Drive a new pinion pin into place while rotating pinion from the front, being sure that headed end is flush or below face of carrier.

10. Place a large punch in a bench vise to be used as an anvil while staking opposite end of pinion pin in three places (again, no illustration).

Note: Both ends of pinion pins must lie below face of carrier or inference may occur.


Not in this section, but in the "inspection" section, it says that the pinion end play should be .009"-.024" (be nice if they suggested a cure if it isn't). The illustration shows using a feeler gauge to measure the end play.

Take care. Tom Worthington
Tom, MUCH APPRECIATED man! I knew I've seen this instruction before, and google sucks so bad nowadays I couldn't find it. I also remember measuring pinion play before and having a spec to compare it too.

I have 3 fucking books sitting here and none of them go into any detail on it. You would think that they would....considering just how important of a roll the planets play!!!




I bought a cheep rear planet set off eBay yesterday to get me by, guy "says" it's good...... Regardless I would like to rebuild this old one, it can't be that fucking difficult. The pins are simply staked into place, drilling them would be a piece of cake.

Really appreciate it. Think today I'll see if I can buy the rebuild kit, who knows if this ebay junk I bought will even be any good..
 

Mr. Breeze

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Sonnax makes this kit
Yup, saw that.

Yesterday I drilled one pinion out just to see how difficult it would be and to see what was causing that pinion to bind up in spots. Fucking piece of cake to drill and remove, needle bearings had pitting and flat/irregular spots, planet case/cage or whatever is absolutely fine, just a needle bearing issue is all.

Nothing hard or difficult about it, only problem I see is how to get a decent crimp on both ends of the new pins. Be nice if the pins came already crimped/staked on one end, that way you could install it and simply back it up with something and stake the other end closed.

Factory units appear to have been machine crimped somehow, unless there's a specific tool sold somewhere out there I don't know about? I'm actually surprised this doesn't come up more often after all these years of 400s being around, guess it's easier for folks to just find another planet set out of something else or spend big bucks for aftermarket planet sets.

I did buy a used rear planet assembly on eBay for 50 bucks, cheep enough but who knows if it will be any good when it gets here. Just amazing to me how this don't come up more often, it seems to be a very simple repair to "KNOW" it's right and in within spec with new needle bearings and bushings!
 

Mr. Breeze

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Well, egay planet assembly showed up today, and I have more questions lol..

One that came out of the trans "mine" is on the left, new/used egay unit on the right, big difference in a couple areas, biggest visual difference is lugs on outside of new unit, it doesn't have the upper lugs.

Also, the output shaft retaining ring is MUCH beefier that my old one.

Other than that everything appears to be the same dimensionally, and pinion gears/bearings/bushings are solid and within spec.


I assume this is just a little different design or later design but still compatible???

Anyone know for sure if it really matters? I like the thicker retaining ring, not sure if it matters though.

Thoughts???

IMG_20211118_165928501.jpgIMG_20211118_165910236.jpg
 
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