Leaky transmission problem
 

So now that I'm putting a few more road tuning miles on my FD, I discovered that my transmission is leaking quite a bit of oil. Before I put her back together, the tranny was thoroughly cleaned, as was the sheet metal cover pan below it. I'm finding a small puddle of gear lube accumulating towards the back side of the cover pan, and pretty much the entire tail housing on the tranny is wet with oil - it appears that the sealant between the tail shaft housing and the main transmission box may be FUBAR'ed and the source of the leak. Obviously if that's the case, the tranny will have to come out and at least a partial rebuild done to fix those leaking joints.

To try to isolate the source of the leak, in case I'm lucky and it's just the tail shaft seal or maybe an overfilled shifter/extension housing blowout, the plan is to clean the mess up, make sure the tranny lube is topped off correctly, then put on some miles and re-check to verify where it's coming from. I don't think I'm going to get lucky on this one though - Looking at how sloppy the sealant was applied on this tranny, I'm guessing one of the car's PO's may have had it rebuilt at some point. Other than the leak, the tranny shifts fine with none of the usual FD synchro issues or funky noises.

I haven't deep-dived the FSM tranny rebuild section yet, so I was wondering how difficult it might be to take apart the tranny and reseal all the leaky case surfaces? More likely, I'll probably just drop my tranny off with a reputable rebuilder for the job, but it wouldn't hurt to check my DIY options.

You need several special tools to disassemble and reassemble and fd trans that most people will not have. I'd take it to a competent shop. While its apart it would be a good idea to change the seals, synchros, and bearings. We do the service for $1899 including parts.

You’re right, first step is to clean it thoroughly and try to trace the source. I think I remember some (gray) sealant hanging out between the housing sections even when my car was pretty new, so not sure I’d be overly concerned at this point.
You might remove the inspection cover on the bellhousing and see if anything is wet. I’m getting ready to drop my transmission as we speak for what I think is a failed input shaft seal. That let gear oil down onto that shield.

There’s also the rear output shaft seal. That can be changed w/o dropping the transmission. I could see the u-joint and drive-shaft flinging oil around, but if you’ve got oil in front of that...

If it's the tail shaft housing, that can be re-sealed somewhat easily, but the trans will need to come out. Just bolts holding it on and you have to do a funky twist maneuver when removing to have the shift rod clear.

Possible someone did a 5th gear synchro job on the trans at some point and didn't re-seal it well.

Good that you caught it, I had a friend with a VERY slow trans leak that he didn't spot and the trans burned up.

Dale

Thanks Ihor, you guys are sort of local and on my short list if it comes to doing a full rebuild. Is that the drop off the tranny & pick it up when done price? I can handle the remove & reinstall myself and schlep it up to NJ easy enough.

I don't think it's the rear output shaft seal, even before clean up. Had one of those fail on my S5T2, and the oil gets flung everywhere in a radial direction centered around where the driveshaft mates with the tranny, including way up in the tunnel. On my FD, that tunnel area is completely dry, only the tranny is wet with oil. Nothing wet seen inside the bell housing with the covers off, so at least that end is good.

I hope it's as simple as that, or a leak from the shifter extension, won't know for sure until I clean it up though and inspect again. Right now the oil is pretty much all over the lower half of the tranny, from the main case box to the tail shaft extension, so it's hard to tell where it came from.

Yes. If you want us to remove/replace the trans add $725.

I opted for Liberty's Gears to rebuild my trans. I went for every option available short of face plating and it'll be like $2,300. I'm also having an oil bar installed to spray cool oil directly on the gears that need it. Picking less options will result in a reduced price.

https://libertysgears.com/our-products/mazda-rx7/

No matter what, you should consider upgrading the main shaft in a rebuild. Reduced flex under load will help save a trans!!

Other than the leak, does the transmission work? If so, it's just a matter of resealing it. Your call on whether you want to pay someone to do that. I don't think it's that difficult to do yourself, especially if the leak is at the extension (tail) housing. If it's at the center housing, it's a little more involved (essentially same process as a 5th gear syncro change, see link), but even that isn't that difficult (you need to fashion an extension for a puller)

3rd Gen RX7

You may try torquing the bolts first (forget if there's access with it on the car). That may buy you a little time if you don't want to deal with it now

This provides a good overview on what's involved with the transmission (at least most of it, the pdf is missing half of the original text)

http://www.billsdiscountgarage.com/f...isassembly.PDF

Thanks for those links, good info there! Definitely something I could tackle, but acquiring or improvising some of the special tools required makes that more of a winter hibernation project.

There's nothing wrong with the tranny other than the leak - it shifts perfectly with no issues & no nasty noises, and assuming it's original to the car, it only has 68xxx miles on it. So yeah, I'd be fine with just resealing it to keep it leak free. So far I've cleaned up the oily mess, and checked/topped off the oil level. It only took a couple of ounces to fill it, so the leak may not be as bad as it looks from the mess it made. Plan is to leave it just sitting on my lift for a couple of days. If the leak makes itself present after that short a time without any driving, the leak would have to be coming from somewhere below the oil level fill line. If no signs of a leak show up that way, I'll take her out and put some miles on & recheck - hopefully by then I'll have isolated the source and gauge how bad it's really leaking

Could you tape colored tissue paper around the seam? That would pinpoint precisely where it's leaking from as it would discolor the dye in the paper starting at the leak.

That's a great idea, but unnecessary now - found my leak after about a 15 mile ride. Wasn't leaking just sitting on the lift for couple of days, so I took it for a spin. It appears that it only leaks when it gets to operating temp & running. Unfortunately it's not something that can be fixed in place. Reference the FSM diagram below, it's leaking from BOTH sides of that plate section I highlighted in yellow, that goes between the tail shaft extension and the forward housing section.


https://cimg9.ibsrv.net/gimg/www.rx7...f11d91ab35.png

So now that I've isolated the leak, would there be any harm if I drive the car but restrict it to short drives and keep checking & topping off the tranny lube as required? I have a lift, and the my FC can keep me entertained on the longer trips like DGRR. Since the tranny has to come out to fix this, I'd like to defer the job until winter hibernation time

If it's a slow seeping leak you should be fine keeping an eye on the level.

If memory serves you remove that piece doing the 5th gear synchro job, I bet it wasn't sealed up well when someone did that job in the past. Also I would read up on the how-to's on the 5th gear synchro, it's quite doable yourself, I've done a few. The only special tools is making a gear puller with a long reach and get some round punches to drive out roll pins. You don't have to take any of the actual gears or anything that's super complicated apart to fix that leak it doesn't look like.

Dale