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View Full Version : Too much diff oil? Symptoms & a mystery....



ScoobyCarolanNC
03-26-2015, 06:55 PM
Hey y'all. I think I may have over filled my diffs a couple of weeks ago. I went on a couple hundred mile road trip & I could smell the hot diff oil. I haven't been under yet though.

When you say a mess, would I see oil in my driveway or spayed underneath? The reason I ask was not only the smell, but after driving 20-30 minutes I get a loose kinda rattle in the gas pedal. I & the dealer have both gone over the front and back ends with no suspects.

I'm wondering if the pressure after the oil heats up is causing some slack in the driveshafts? The feeling goes away after its cooled off. It's conceivable my breathers are blocked or constricted its a 2010 with 70K on it. I used Lucas Oil 80W-90 gear oil with LSD additives (lol) if that helps at all.

olram30
03-26-2015, 08:17 PM
Open your fill plug, if it pours out, then it's over filled.

ScoobyCarolanNC
03-26-2015, 08:25 PM
I got that part, what of the rest? Am I crazy & don't understand how this works? How do I check the breathers & where would I have seen oil? I've seen it said "just fill her up to the hole" & I've seen "measure precisely".

seanb123
03-26-2015, 08:29 PM
You are over thinking it. Calm down. Get on flat ground or on a lift. Open the hole in the diff cover. If nothing comes out and it's close to the hole your fine. If it comes out wait til it stops and then put plug back in

jnabird333
03-26-2015, 08:34 PM
Do you have an aftermarket diff cover? If so what one?

Some aftermarket covers have a higher fill hole and if you fill to this height you could overfill and cause a hot puke issue.

thardy
03-26-2015, 08:43 PM
Do you see any spray under the vehicle at all? How much gear oil did you put in each diff?

toxicwaste29
03-26-2015, 09:07 PM
Breathers can easily be replaced. First pull it off the diff and see if you can blow air through it. If so its not clogged

JKAnimal
03-26-2015, 09:33 PM
Avoid the LSD additives they are making your diffs trip out!

But seriously What everyone else said.

Personally I like to run full synthetic. It can take the heat better than dino.

I have seen a case of someone running too low a pressure in their tires on the road, and driving too fast, causing the diff oil to boil and have the hot puke issue. Although I'd think you would know if your tires were that low. :hmm:

ERAUGrad04
03-26-2015, 11:19 PM
When I just had my gears done, my front diff was slightly over serviced. About 100mi into the trip home, I stopped at a gas station and smelled gear oil. I found the front left undercarriage misted with a fine coat of gear oil. It was coming out of the diff breather. Once I got home, I had completed the 500mi break in and it was time to change the oil out and perform an inspection. Before I drained the oil, I pulled the fill line plug and a bit of oil came out.

I serviced both diffs with Royal Purple to the fill line, not over, and I haven't seen any signs of puking in nearly 1,500mi.

jeeeep
03-26-2015, 11:27 PM
Hey y'all. I think I may have over filled my diffs a couple of weeks ago. I went on a couple hundred mile road trip & I could smell the hot diff oil. I haven't been under yet though.

When you say a mess, would I see oil in my driveway or spayed underneath? The reason I ask was not only the smell, but after driving 20-30 minutes I get a loose kinda rattle in the gas pedal. I & the dealer have both gone over the front and back ends with no suspects.

I'm wondering if the pressure after the oil heats up is causing some slack in the driveshafts? The feeling goes away after its cooled off. It's conceivable my breathers are blocked or constricted its a 2010 with 70K on it. I used Lucas Oil 80W-90 gear oil with LSD additives (lol) if that helps at all.

x2 on removing the plug and seeing what drains out, if you have the stock covers and you get drain off, then yes they are overfilled. If you have aftermarket covers then you'll need to estimate the amount needed, it should be filled to 1/2 the axle tube.

you won't see a mess in your driveway, you'll definitely smell it but the signs it's too full will be on the breather valve/hose and usually on the control arms or underbody. follow the breather hose off the axle to the end of it and you'll see a white colored cap - this is the breather, like this:
133485

all the oil on it is from the service shop overfilling my PR44 - I know, should have done it myself.

The overflow will not cause slack feeling, too much LSD additive will. I would drain the axles and use synthetic, no additive needed and it seems to take the heat better.

cheers :beer:

ScoobyCarolanNC
03-27-2015, 01:56 AM
Fellas! This is all the info I needed, thank you all so much. Extra props to Jeeeep for the photos & the "slack feeling" comment. I could never think of the right word to describe it. Should I be worried about that and flush the whole thing again?

ScoobyCarolanNC
03-27-2015, 02:53 AM
So I just flushed & refilled it. Long story why, I just felt better this way. No signs of spay underneath, but the old oil was warm and when I pulled the fill, it poured out both.

When I pulled the drains to finish, there were no large chunks. Just what I had hoped. Much more careful refilling & made sure overflow had stopped before I sealed it up (didn't originally).

Slack is heavily reduced after ten minutes on the highway by comparison, but still there. The Lucas Oil is rated "above Gl-5" specs and says heavy duty, maybe it's just not the right product for this application.

Anyways, thanks again to everyone for the tips, photos, and more. I'm gonna run it as is for a while and switch to the MOPAR and report back.

Maybe I over filled my t-case with ATF+4 too? I'm gonna give that a look tomorrow. I'm a newb...

jeeeep
03-27-2015, 03:34 AM
So I just flushed & refilled it. Long story why, I just felt better this way. No signs of spay underneath, but the old oil was warm and when I pulled the fill, it poured out both.

When I pulled the drains to finish, there were no large chunks. Just what I had hoped. Much more careful refilling & made sure overflow had stopped before I sealed it up (didn't originally).

Slack is heavily reduced after ten minutes on the highway by comparison, but still there. The Lucas Oil is rated "above Gl-5" specs and says heavy duty, maybe it's just not the right product for this application.

Anyways, thanks again to everyone for the tips, photos, and more. I'm gonna run it as is for a while and switch to the MOPAR and report back.

Maybe I over filled my t-case with ATF+4 too? I'm gonna give that a look tomorrow. I'm a newb...

do you have a manual or automatic?

what size tires are you running?

too much fluid in the transmission/transfer case can cause slipping. if you're running a bigger tire and have an automatic, did you recalibrate for the tire size? not having the tire size/ speedometer calibrated in an automatic will make it feel like it's got "slack" on take off.

ScoobyCarolanNC
03-27-2015, 04:04 AM
Hmmm, the plot thickens. Thanks for hanging in there with me on this.

She's an automatic & keep in mind I've only owner her a month, so I don't know everything about her past. That said I have noticed some things.

Red (her name) came on 275/65/18s. When I compared the difference to 255/70/18 is was minor, but maybe 1/4-1/2" larger in diameter & 1/2-3/4" wider. As far as I know, nothing was recalibrated as the difference was .02 mph at 60.

I know she had a transmission coolant line replaced during the CPO inspection. I haven't messed with that yet even though I bought a filter & everything I need to pull the cover & flush.

I also noticed on the rear drive shaft that there was a new looking part number sticker. I thought it was odd, but dismissed it. The shaft had a normal amount of rust from exposure, but the sticker looked pretty much whole & not as worn as I'd have expected if it was 5 years old.

The diff oil was old when I changed it originally & both plugs had a fair amount of fine sludge, but no shavings. However the transfer case oil was fresh & red. Maybe that doesn't wear, had been serviced recently, or who knows.

Well, that's about everything I know or have seen so far. Maybe the transmission has some issues due to over heating in the past? Maybe a new driveshaft was improperly installed? Maybe I overfilled the transfer case like I did the diffs?

ScoobyCarolanNC
03-27-2015, 04:06 AM
I'll say this though. She pulls hard and I've never felt slipping in the tranny. Just slack in the drive line, steering is tight side to side, no dead zone.

COLOMW3
03-27-2015, 11:59 PM
Hmmm, the plot thickens. Thanks for hanging in there with me on this.

She's an automatic & keep in mind I've only owner her a month, so I don't know everything about her past. That said I have noticed some things.

Red (her name) came on 275/65/18s. When I compared the difference to 255/70/18 is was minor, but maybe 1/4-1/2" larger in diameter & 1/2-3/4" wider. As far as I know, nothing was recalibrated as the difference was .02 mph at 60.

I know she had a transmission coolant line replaced during the CPO inspection. I haven't messed with that yet even though I bought a filter & everything I need to pull the cover & flush.

I also noticed on the rear drive shaft that there was a new looking part number sticker. I thought it was odd, but dismissed it. The shaft had a normal amount of rust from exposure, but the sticker looked pretty much whole & not as worn as I'd have expected if it was 5 years old.

The diff oil was old when I changed it originally & both plugs had a fair amount of fine sludge, but no shavings. However the transfer case oil was fresh & red. Maybe that doesn't wear, had been serviced recently, or who knows.

Well, that's about everything I know or have seen so far. Maybe the transmission has some issues due to over heating in the past? Maybe a new driveshaft was improperly installed? Maybe I overfilled the transfer case like I did the diffs?

I'm still trying to figure out how you overfill the transfer case or diffs... pump like hell and slam the plug in? How much could you possibly over fill? Your transfer case doesn't get near as hot as the diffs so the oil will not break down. My JK is 3 years old and my drive line is the same, sticker is pretty but shaft if all rusted. I think they just have good stickers, my springs have the factory stickers and they look brand new also and they've been covered with everything ,snow, mud ,etc. BTW I use Royal purple in everything, don't have to deal with additives and such.

ScoobyCarolanNC
03-28-2015, 01:47 AM
Oh I have my ways..... Honestly, I didn't think I pumped like hell and it was dripping a bit, not pouring out. I locked it up thinking I was ok. Honestly, I've spent weeks going through a million other things as my issue, this seemed pretty crazy. When I opened the fill on the front diff maybe 5-6 ounces drained. The oil was warm so I don't know if that caused more than if cool.

Thanks for the info on the stickers t-case oil. I found it odd that original factory parts had these stickers. I feel better knowing that I probably don't have a replacement shaft.