Strat

Looking for some input here. Dealer recently replaced rear dino differential fluid with synthetic and shortly thereafter the seals failed and leaked into rear brake drum. This in turn warped the front rotors which were only a few months old themselves. The car is a 2000 4runner 4x4 with 138,000 and has had no abuse.

My take on this is that the dealer should never have replaced the fluid with synthetic on a high millage car but the dealer insisted that synthetic really didn't have anything to do with it, that the seals were ready to go anyway.

Does anyone agree/disagree with me? I think I need to go back and fight this one.

BajaRunner

The synthetic is thinner in some cases, and also contains cleaning agents, which will in turn get rid of gunk (Well, this is the case for motor oil, I am assuming the same for diff oil).

My good friend who has worked at a dealership for over 30 years swears by dino oil, and won't use anything else. I too have had unsuccessful results with synthetic.

Don't know what you could really get out of the dealership though. I mean, the seals were probably ready to go. Its too common of a problem in 3rd gens it seems.

One_96TR4

I'd try and fight them and see what they say. Pretty sure you won't get anywhere though. Like SC4runner mentioned it's a common problem.

toy_tek

Coincidental and unrelated. At 138k you were right on schedule for a rear axle seal leak. I put synthetic in the rear diff at 100k or so and got my first leak 2 years later at 140k. Unrelated.

Also search here for front brake info - don't replace the rotors with OEM or cheapies.

waskillywabbit

iTrader: (-1)

X2

mkgarrison5

exactly.... i have been using syns in my diffies for 67k miles from mileage 52k miles to my current 119k miles.. no leaks no nothing... your seals were ready to go before you put the synthetic gear oil in. replace the seals and use whatever gear oil you want syn or not....

rotors-- brembo blanks seem to work very well with oem pads.

algranger

I agree with SC4Runner, the synthetic can leak in places conventional doesnt. Doesnt mean synthetic was a bad choice it just means you should have replaced your seals, sounds like they were starting to go.

mkgarrison5

describe unsuccessful???? did your unit or motor lock up from using syns?? highly doubtfull... tons and tons and tons of UOA's done on syns and dino motor oil and gear oils. no failure to date due to using syns. only failure to maintain on the owner's part.

eatmorechicken

Very possibly related. I have seen seals leak due to syn several time. Well its not that syn makes them leak, its more that regular oil stops them from leaking. The petroleum in regular oil soaks into rubber, rejuvinates it and causes it to expand ever so slightly. Synthetic, not so much.

X-AWDriver

138k and you just got the leak? You might've been overdue;my '97 and '99 both leaked just shy of 100k and my mom's '99 Limited's seals went just a few months ago at 90k.

I've been using Redline fluids in my diffs for 40k miles since I replaced my seals and they are fine.

It's coincidence.

Victor

I have synthetic in both axles, tranny, and transfer case as well as the motor. The 3rd gen seems to have more reports of axle seal leaks so that should be part of your maintenance schedule just like a timing belt.

trbizwiz

I just put amsoil 75w90 severe gear full synthetic in my front and rear differential on my 92 PU. I used amsoil's pump to get it in there. That stuff seems pretty thick to me. I did not even do a very good job prepping and sealing the diff to the rear Axel and no leaks there. I think the synthetic oil is too thin argument is BS. The cleaner additive argument might make sense, but would the dino lubes not have similar cleaners in them too. And what properties would allow the dino lube to "absorb" better than synthetic? I am not trying to start an argument, just want the info.

rearviewmirror

Of course it's thick when it's cold..... Synthetic oils is generally thinner than a comparable weight dino oil. But that argument is like 20 years old now. Look what you used... 75W-90.. 75W when cold...

My axle seal leaked @ 50k miles, of course the 4Runner was 7 years old. I'm running Mobil1 in the front/rear diff and transfer case now.

trbizwiz

agreed, but to a nube, reading all this stuff about synthetics being so thin, it sounds like the stuff is like water, it certainly isnt. It is probably relatively thinner, I would question if this creates leaks.

mkgarrison5

there is a minor difference in the thickness of dino and syn in comparable weights but not enough to "cause" a leak.. the syn cleaned the seal off and it started leaking. who the hell said that dino oil is absorbed in a seal?? uhhh proof? if anything it gunked up the seal making it appear that nothing was wrong and the syn exposed the leak... i can see an additive like in high mileage motor oils that causes it to swell but thats it... you were just due for a new seal....

dbcx

X2 Everybody wants to blame syn oils when they swap.Parts do wear out and it was time for seals. The syn oil prolly cleaned all the gunk,Its doing its job. Replace the seals put syn back in it and your good to go. We hammer the severe gear in our dirt race cars and we have not had a failure yet,as before we were having issues years back.

TC4RNR

i have been on the road alot after i bought my 99, at that time, it had 120k miles, i put Redline 75-90w in the diff. front and rear. they were good till i got airborn couple weeks ago at Pismo. the driverside rear axle seal gave up, now it has 140k on the dail. so i won't say it's the synthetic oil made the seal to leak.

crolison

inner axle seals are easy to replace.

dbcx

The synthetic didnt cause your seals to leak ,it caused you to get airborn since your friction was less. So I guess the synthetic made your seals leak just like everybody says it does

mkgarrison5

i have been using a mix of 75/140 and 75/90 (50-50) severe gear oil (Amsoil) in my tcase and diffies for some time now and no leaks :-).... but when i do eventually get a leak ill blame it on syns .... i love amsoil