Transmission Block off Plate leak

[JAubin]

So after getting the motor/trans all installed I finally got around to picking up some fluids and added some Motul 75W90 to my gearbox. Everything looked good, no leaks. Next day there was a small puddle near the back, with droplets forming at the bottom of the block off plate. I had installed it when I did my LSD install a while back, so figured I must have rushed it and made a mistake. Drained the trans, pulled plate off and it looked like near the bolts had little to no Hondabond in that area...so I cleaned up the entire gasket surface again, reapplied, screened the oil, and looked good...And now I still have the same leak. @#*& It's very slow but obviously not good...I think I need to pull it off again and double check for any burrs, etc. on the plate. Did anyone else run into this, and something else I may be missing? I did deburr the plate before assembly but it's definitely possible I missed something.

[STiPWRD]

It sounds like you did everything correctly. As I recall, I had to sand the edges of my block off plate to fully get rid of the burrs. You could also check flatness of the plate and trans mounting surfaces with a feeler gauge and straight edge tool like this: http://www.jegs.com/i/JEGS-Performance-Products/555/81640/10002/-1?parentProductId=957599

[Bob_n_Cincy]

So after getting the motor/trans all installed I finally got around to picking up some fluids and added some Motul 75W90 to my gearbox. Everything looked good, no leaks. Next day there was a small puddle near the back, with droplets forming at the bottom of the block off plate. I had installed it when I did my LSD install a while back, so figured I must have rushed it and made a mistake. Drained the trans, pulled plate off and it looked like near the bolts had little to no Hondabond in that area...so I cleaned up the entire gasket surface again, reapplied, screened the oil, and looked good...And now I still have the same leak. @#*& It's very slow but obviously not good...I think I need to pull it off again and double check for any burrs, etc. on the plate. Did anyone else run into this, and something else I may be missing? I did deburr the plate before assembly but it's definitely possible I missed something.

How long did you let the hondabond dry before putting oil in the transmission?

[JAubin]

Thanks STiP, I'll plan on sanding the edges a bit more and look for burrs on my next go-around.

Bob, the first time was probably on the months timeframe as I rebuilt the trans a while ago. The second time was likely around 20 hours or so.

[K3LAG]

I found the bolts for mine were a little too long and were reaching full tightness before the plate was tight. I used slightly shorter bolts. Wow, that was 18 months ago or more, I hardly remember back then. :)

Larry

[redfogo]

When it comes to sealing off oil I have always had the best luck using "Permatex right stuff". Never had any issues with it, it seals very fast and always seals the best I have found.

[JAubin]

So quick update here: Larry, Thanks for that idea, I threaded a few bolts in and measured, and they all bottomed with adequate (but not a ton...) travel to compress the plate. I think it was ~2mm of additional travel, so certainly borderline!

red my Honda Bond tube was getting low so I picked up some of the Right Stuff to give that a shot.

I picked up a better gasket scraper and spent a bunch of time cleaning every remnant of rtv on the transmission. Then went over it with some solvents to clean it up more. The plate I had done a pretty good job deburring the outer surface, but hadn't done as much on the inside. I added a small bevel to all the edges, and inside the holes all around. Sanded the edges a bit too to make sure I didn't create any problems doing the work there. Cleaned that surface as well, and then applied the RTV bead to the face of the transmission side. tightened all the fasteners to finger tight, then went around in a criss-cross to but seat the plate/gasket, then finally torqued it to final (~30 ft lbs). Waited about 48 hours to add oil, and then filled it up. 24 hours later no leaks! 48 hours later....aaaand there looks to be a small amount that dripped out (like 2-3 drops)....I'm starting to question if I might have a leak/crack along the back of the case vs this flange....have to see if that was a fluke or if it keeps leaking.
If it still is I may let it leak to the point that it's below that level and then address it later on when I can bring it to a shop...I think I'm getting close to the limit of my skill/ability if I'm dealing with a flatness issue that will require machining. At least I can replace the Center Diff housing portion of the transmission without pulling it....

[STiPWRD]

Sorry to hear you're still having leak issues, it sounds like one of the mating surfaces is warped. If you decide to crack it open again and try to fix it here are some tips:
1. Check flatness of each surface with a straight edge (one that is accurate to 0.001"). This should tell you right away if something is warped - either the plate or the transfer case housing.
2. Take lots of pictures during the process. This will help us pin-point a not so obvious issue causing the leak.

[JAubin]

Thanks STiPWRD, I think I may have found the culprit...I cleaned off the entire area again and put rags stuff in multiple locations to figure out the spot...I swear I checked this before, but it looks like there might even be some RTV leaking out from the bolt hole or something...either way, it helped highlight the crack along the fastener boss. Unsure of when/how this happened, but looks like it's the source, sorry for hte poor photo, just snapped it while taking a closer look. At least the flatness/RTV on the back plate is ok, just need to get a new housing off a trashed transmission now!

46084

[redfogo]

Hard to tell from the pic but you might be able to use Jbweld to patch the crack.

[Mechie3]

I cracked one too but one that was external. I had some silicone in the hole and it created a perfect seal. The air in the bottom became so pressurized it popped the entire back side of the boss off the housing.

[Ironhydroxide]

I've seen that happen a lot. If you need a new case I have quite a few I'd sell you one.