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Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Transmission - Rearend> T-400 direct drum grinding on center support?
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Topic Review (Newest First)
09-15-2012 01:27 PM
Crosley thanks for the update. Mistakes in these transmissions can be expensive

09-15-2012 11:48 AM
Mr. BBQ As much as I HATE bumping a dead old thread I realized I completely forgot to post my results. I did end up finding the problem, much to the dismay of my ego

After completely disassembling the trans I spent some time staring at the parts. I quickly noticed the output shaft had large gouge around the base, on the side that faces rearward. (From memory...I can't 100% verify that...) Regardless, as it turns out I did forget a part. It was the most rearward torrington bearing.

What ended up happening was the output shaft was grinding on (whatever it sits in front of, can't remember now) and filled the trans with metal filings.

This in turn caused the entire assembly behind the center support to drop down, which caused the sun gear shaft to drop down, which caused the drum to hit the center support, and grind away as well.

EDIT: To clarify, the output shaft had enough material ground away from it it dropped the output assembly down/rearward, probably over 1/8th an Inch. This magnified the missing 1/4 in or so from the missing bearing to create one hell of a chain of events.

The end result, a pan FILLED with metal, a plugged filter, a botched tranny rebuild, and a bruised ego. It has a happy ending though, I re-rebuilt the trans, correctly with ALL the parts this time , and reinstalled. After that it worked GREAT, shifted spectacular, no more metal in the fluid I was very happy with the results after.

Anyway, thought I'd finally post an update. Unfortunately the truck is sitting at my parents and only gets used occasionally as a beach truck, as I've moved into a neighboring state. Someday soon however...
03-09-2012 06:37 AM
trannyguy
t400 direct drum grinding on center support

re-check your sun gear. chamfer should be down towards rear planet.installing it with chamfer up may have allowed the sun gear shaft to be down too far allowing the drum to be closer to the support.hope this helps.
03-08-2012 11:54 AM
jakeshoe Something was mis-assembled. Just gotta find out what.

As for the cup plug, it is used when dual feeding and using an OEM separator plate to prevent loss of 3rd gear oil out the reverse passage/circuit, and exhausted at the manual valve. It needs to be there when dual feeding with a stock plate.

The direct drum can be supported on the forward hub using a 4L80E forward drum bushing and some minor machining.
03-07-2012 09:40 PM
rick 427 And if you say yes to that,then i'm gonna have to put my bat away...I've hit enough balls to the warning track on this one....other than mis-matched parts,and i don't believe the trans would even go together that way,sans the center support,,if you find what I haven't covered,you win the home run derby......oh,and my 1st posts was a mis-read from me,as i thought that the drum was eating the teflon rings,not the drum kissing the center support,,,sorry about that.
03-07-2012 09:28 PM
rick 427 and you got the 3 piece bearing on the 1 side of the output shaft,and the 4 tang washer and the 3 tab case washer[that goes on the case] on the other side?? Is the case worn where the 3 tab rides?? Is it the right thickness 3 tab washer?
03-07-2012 09:14 PM
Mr. BBQ I'll double check the splines tightness in the drum, but I don't remember it being particularly loose. I do remember the splined shaft being a good fit in the center support however, I'm still certain that bushing was good.

I did check that bearing under the sun gear as I originally thought that was the problem, but it was in place in good working order, all 3 pieces were there. I even made sure I put the sun gear in correctly, all was according to direction in the ATSG with the chamfer end facing up.

I did note how the splined shaft looked to support the drum where it seated. I mean at the base of the splines where it goes into the direct drum. it looks like the direct drum is worn on that surface as well but the shaft isn't. I have 2 shafts to compare it to. Whether it was worn there before or not I cannot say for sure, but it is worn enough to let the drum drop down onto the center support. This seems like another possibility?

EDIT: Omit that last idea, I had a total brain fart. I was thinking of where the drum was hitting the center support, not where the splined shaft seated. That's what I get for thinking at night I'm going to double check the splines however for wear anyway.



Front endplay was perfectly in spec, rear was in spec as well but towards loose. I've been reading its better to spec it towards the tight side now, but I wouldn't know if this could cause this much problem?

Tomorrow I'll have to dig into it more and see if I can find more plausibilities. It is a pain in the butt being inexperienced with this, but dammit I will learn one way or another!

Thanks a million for the help thus far guys! I do appreciate it!
03-07-2012 08:54 PM
rick 427 good point Crosley...but it still throws me off on why the problem wasn't there when he took it apart the first time...only after 25 miles or so of driving after the rebuild.......ok Mr BBQ...listen up....I have a gear train in my hand...the teeth on the top of the sun gear shaft spline into the drum...the drum bottoms out at the end of the teeth,preventing it from making contact with the support,now heres the good part...on the other end of of the sun gear shaft is a 3 piece torrington bearing that it, and the sun gear,rides on..if that bearing or a part of it, is missing,the sun gear shaft will be lower than its supposed to be...and when the sun gear shaft is lower,it is lowering the back of the drum allowing the drum to make contact with the support....you might be missing a bearing back there....please double check that
03-07-2012 08:18 PM
Crosley How do the splines fit from the tube into the direct drum? Are they loose ? The drum can wobble around if the splines are loose

Typical drum wear of this type is from loose bushing in the center support on this tube. It allows the drum to drop down. The sealing rings are not there to support this drum.

You say the end play was slightly loose? If you are talking about the front end at the pump, this can allow the drum to move around some and forward slightly. This can allow the drum to wobble.

There is a bushing available from CK Performance in New York area that fits into the direct drum on the front side and aligns with the inner drive hub that sits inside the forward drum (input shaft drum). This is not a drop in repair, some machine work is required.
03-07-2012 07:03 PM
rick 427 What makes this situation bad is that it was rebuilt by who knows who before you got your hands on it and you being,addmittedly, inexperienced.....if this trans was never run,you could have inherited a problem from the previous build......man,I don't know,wish I was looking at it. Instinct alone tells me if something isn't right when putting them together. Little harder trying to visualize it.
03-07-2012 06:54 PM
Mr. BBQ From what I remember of rear endplay it was in spec, but on a looser side. The exact number I can't remember. Front endplay was was directly in spec.
03-07-2012 06:51 PM
rick 427 did you check end play when you got the back half together?
03-07-2012 06:41 PM
Mr. BBQ Hmm, good to know on the plug, I'll be sure to replace that then. I'm not 100% convinced that would create my problem though, I'll have to look into that.

There were 2 different height center supports, in my ATSG manual it said the difference was whether or not you used the fretting ring beneath it (I think, I know it was the difference of one snap ring) and I do remember measuring to make sure I needed the extra snap ring. I tried doing some research and couldn't find anything about mismatching a direct drum and center support, so I'll shelve that idea for the time being.

EDIT: I can't remember exactly how the ring went in. I want to say I had to wiggle it in a little but I don't remember it being stubborn enough I had to tap it in. But for what its worth it didn't just slide in like butter either.
03-07-2012 06:26 PM
rick 427 A flat steel was used to replace the wavy steel in a lot of rebuilds by guys...the whining noise was just the filter trying to digest all the metal i'm sure it ate...I've never put a solid cup plug in ANY port,unless a step in a valve body reprogramming kit told me to...restrictor plug, yes..solid,no....and every kit that I have installed,gave me a restrictor plug,never a solid one...unless we're talking full manual shift,which we're not this time...if it's the cause of the problem or not,i'd remove that plug if its not part of a kit....but thats just me...still thinkin...i've seen this same problem before,but its been a while.....wait...there were 2 different height center supports for the 400's....but i'm not sure what ill effect it would have by using the wrong 1 ...i've never mis-matched them....and if that trans was never run when you got it....but i'm thinking if the thin 1 was used where it called for a thick 1 that it would smack the back of the drum,even tho that would usually happen after it breaks the support to case bolt.....tell me, did that beveled snap ring go in easy?....or did you have to tap it into the groove fully with a hammer and screwdriver to fully seat it??
03-07-2012 06:00 PM
Mr. BBQ I'm fully aware of the problem I created

I didn't change any bushings as they all looked fine, and even now don't look damaged. The center support bolt was still tight when I took it apart, and I did torque to spec when I installed originally. I did install the snap ring bevel up, I noted that when I was taking it apart, and was fully seated.

The intermediate clutches I was very anal about installing correctly, however I did not have a wave plate with it. Now, its possible it could have been missing from a previous rebuild by another hand, as I saw evidence of this (a shoddy one at that with over torqued bolts galore). The truck it came out of had been sitting for ten years so there weren't many if any miles on it. So this could be a possibility I suppose. I guess this one boils down to how to know exactly if a waved plate is supposed to be used?

I did use a solid cup plug in a case, 3/8" if memory serves me. The lube problem could make sense if maybe my pump had gone bad? I forgot to mention the pump had started whining after I lost all the gears limping home, I was thinking this was because the filter was so plugged from all the metal shavings that it was starving for fluid, but a dying pump losing pressure would make sense as well. I guess I'll have to check the pumps condition.

I will also mention that in my tireless reviewing of my rebuild I remember when I installed the scarf cut seals, for some stupid reason I made a seal compressor I had seen used for the SOLID teflon seals. I'm not sure if or even how that could have damaged or altered the seals function but I'll mention it regardless.
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