Rear main seal leak

Ed Bravo

On a Baja trip two months ago I noticed a slight rear main seal leak - 2006 Tacoma V-6, 4.0L with about 150,000 miles. It's still very slight, a drip or two per day. So, do I just let it go until it gets worse? I figure the repair will be pretty costly to install a relatively inexpensive seal. What's your experience? Will it turn into a gusher overnight?



Expedition Leader
With most vehicles you usually can let it go for a while so I assume it will be the same for a taco. I had a broken rear seal on one of my scouts for a very long time. Just be sure to check the fluid level every so often. Only possible problems I can think of are water crossings. You wouldn't want to mix the oil with water obviously. I've heard working on toyotas is fairly simple so I would guess a repair would go in the $700-$800 range.


Buy Once, Cry Once
I had a rear main seal start leaking on my Ranger around 160k. I switched to Valvoline High Mileage and it wouldn't leak until the oil was about 2.5k miles in, I'd let it leak until 3k then change it. Other than making a mess underneath it never bothered me. If it was leaking faster, say a quart every 500 miles I would have replaced it.

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Expedition Leader
My '05 has stared leaking recently also; I think it has around 120,000 miles on it. I'm not real happy about it but I plan to let it go as long as it doesn't cause clutch issues. When it starts to be a problem I'll replace it along with the clutch assembly. The rear axle seals on the other hand will probably be getting replaced on my next trip back to the US. If I'm not too lazy I'll replace the front bearings and seals also.


New member
My 06 4 runner has had a leaking rear main seal for a few years now. Dealer quoted me like 1600-1700 for repair. I still have yet to have a drop on the driveway lol.

Ed Bravo

Valve cover? Hadn't looked closely. We took it to a Toyota dealer in San Jose del Cabo who diagnosed it, showed me what appears to be an inspection cover and the oil was coming from inside, but I will take a look as you suggest. The dealer didn't have the part in stock. Guess we should have waited the three days to get the part, the scenery and fun would have been worth it. I believe he quoted us between $350 & $400 U.S. dollars. It appears that would have been a bargain.

I appreciate the advice and ideas of the responses.



Get Dirty.
It could be either or both. Valve cover leaks have a tendency to fake out people on first inspection. They leak down the back of block and appear to be a rear main. If they pulled an inspection plate than they are probably right.


Good points about double checking to verify if it is the rear seal or a valve cover. $400-500 range is about right for replacing the rear seal. Most of the cost is for dropping then reinstalling the transmission. What could run it higher though is if you have a manual transmission and the clutch was oil soaked because the seal blew out thus should be replaced as well.

Each day you run with a leaking rear seal is playing roulette. Do I have 20k miles or 20 miles till it blows out? No way to tell... If it does blow out, the truck will only get 1 to 5 miles until the oil runs out leaving you stranded on the road or the trail. You can limp the truck in short jumps if you can get ahold of a case or two of cheap oil to top up the oil then limp a very few miles followed by filling with oil again. The truck will be trailing an outrageous smoke screen from oil on the hot exhaust and probably flinging oil on cars unfortunate enough to be behind it.


Meandering Idaho
My vote.
Fix it now.

Take it to the stealership and then also get a quote from a good import/ toyota shop.
The latter will almost always be able to beat the former.

If you fix it now its one of those things that you know is done and you wont have to hopefully worry about again.


Get Dirty.
The last time I did one I also replaced the front pump seal, flexplate, torque converter bolts, rear main, and switched out my trail spare starter for a new one. It took 7 hours on a lift.

Ive done it on a gravel floored shop, 13 hours. Mainly wasted removing and installing transmission. Had to use a forklift to get enough height to slide it out from underneath.