Differential Gaskets

[sparks57]

I am going to drain my differentials and refill them. I have already done the transmission (with a quart over) and transfer case. The only thing that has hung me up is whether there are gaskets I need to get that go on the differential covers. Or do people just use blue stuff?



God knows when all the fluids were drained from this truck... I'm setting up a regular maintenance schedule for everything on the truck. I'd wrather pay a little now and not a whole lot later.



This weekend is the first true test of my truck. I need to go down to mud lake and pull a trailer back with 5 tons of hay over Gilmore Pass. It's a long uphill pull untill the other side. I'll just keep her out of fifth and keep my fingers crossed.



Any other suggestions would be welcomed.

 

[paccool]

The blue stuff! Or the red, black, or whatever color you like the best. There are no gaskets, just a good sealer. This may turn into something like an oil discussion before its finished, there are lots of choices.



While you are under the truck, make sure to look at the inside of the rear wheels for any oil leaks that would indicate a seal leaking and check the U-joints for play.

 

[Philip]

I use good gaskets myself. I leave the blue goo alone most of the time. Any good auto parts store will be able to get gaskets for you. The model 60 and 70 are common axles in the auto industry. These should be shelf items.



I normaly do a chassis fluid changes around 35k or so.

 

[sparks57]

Ok, you've got a novice here. What is a "U-Joint"?



As for oil, I put Mobile 1 in both the transfer case and the transmission. I have regular 90 weight gear oil for the differentials.



I understand that you should use good synthetic for the transmission and stuff... but I thought gear oil was gear oil. Or maybe I misunderstood.



I was also told that I may need a friction modifier. Do I? I thought it was only with limited slip and that there is a tag that said if I had it or not. I don't rightly remember...

 

[Philip]

A u-joint is a flexable connection used in a driveshaft to allow it to drive power to two device that are not on the same drive plane. (I. E. the transfer case to axles).



This website shows a picture of a u-joint.



http://www.jeepaholics.com/tech/ujointconv/ujointconv.htm

 

[paccool]

There are 3 U joints on the drive line. There is one at the rear of the transmission, one in the middle of the drive line and one at the rear end. They allow the shaft to flex as the truck moves up and down. If they get bad you can sometimes hear a "clunk" when letting off the go pedal or feel a high speed vibration at certain speeds.



At the minimum, check for grease fittings (zerks) on the joints and give each one a couple shots of grease if there are zerks present.



Yes, you will need a friction modifier if you have limited slip in the rear diff. 90 weight is ok if you don't do a lot of heavy hauling all the time. A multi weight is better if you do pull heavy loads pretty often. (85-140 wt or 75-140, depends on whose oil)



Synthetic gear oil is like the synthetic motor oil, is supposed to take heat better without breaking down. I like it cause I don't have to change as often as with regular gear oil. Some synthetic gear lubes say you don't need a friction modifier, I still had to use some in mine due to chatter.



Maybe someone else will jump in hear and answer this better than I have.



Stan

 

[paccool]

Sorry Phillip, I type slow and didn't know you had already replied about the U-joints



Stan

 

[Paychk]

Here Ya go:



http://www.cybrrpartspro.com/Chilton Manuals/8847m/8847CH07_4_IDX.HTML

 

[paccool]

Good info Alan. How do you guys find all this stuff?



There is usually so much stuff that comes up when you do a search that it is hard to weed the good stuff out. Will save this info for future reference!



Stan

 

[Paychk]

One word... ... . GOOGLE and a little luck. But usually I'm looking for something totally different and stumble upon interesting things so I bookmark for latter. Then go back as time permits and dig deeper.

 

[DKasper]

Good question! I'll add my experiences with differential fluids/Gasket material comapatability.



I have found that when using regular(read "non-synthetic") diff oils, that the blue RTV or pretty much any other color, works just fine.



I went to Royal Purple synthetic fluid in my differentials and found that plain RTV sealant works fine for about a year, then I developed leaks in both front and rear within a month of each other. I checked with Royal Purple and they suggested using a non-RTV gasket-maker type of material. I chose the "Great Stuff" gasket material available at your local NAPA store. It's kind of pricey -- about $16 for a spray-on can -- but after 3 years, no leaks.



Good Luck!



Dave

'99 Dodge 2500 TD

'82 Ford w/Deutz F5L912

Soon to add: '93 D350 TD !

 

[sparks57]

Oh no... . My truck makes a clunking noise when I let of the pedal. It also makes a clunking noise sometimes when I set off from a stop sign.



This is not cool... I have heard U joints are expensive. What do I need to do?



Man, one thing right after the other...

 

[JFitzgerald]

CB, check those u-joints for play. You may have some play in the rear ring & pinion, like I do. It can sound pretty loud due to ringing through the long, hollow driveshaft.



I use silicone for my diff covers (I prefer the black ). I change the gear oil in the axles and transfer case once a year, which is around 25-30K miles for me. Regular 80-90 weight, non-synthetic. Not that synthetic is bad, I just don't think it's worth it for me except in the Getrag. The trans oil gets changed at every other engine oil change. Just changed lube in the engine, trans and rear last weekend. Found Mobil 1 in a gallon jug this time. Got a few pics while I had the shifter out of the trans if anyone wants to see what's involved with that method of overfilling.



BTW, CB, Did you mean you used Mobil 1 motor oil in the transfer case, like what the Getrag uses? I'd use gear oil in the NP205.

 

[sparks57]

Chiltons called for 10-30 for the T-Case, so that's what I used. I know chilton's isn't great, but I did what it said. Should I have used gear oil?



I'll check the driveline after school.



The seems to be underneath me more than anything, not up front or from the back. Maybe it's the front U Joint. I don't know.

 

[Philip]

The Dodge manual calls for 75/90 gear oil in the NP205 transfer case. I use a syn in the transfer case. In the axles I use regular gear oil.

 

[Paychk]

The 93 factory manuals states the following for the NP205:



engine oil SF/CC or SF/CD SAE 30 below +32° F and SAE 50 above +32° F



or



SAE multi-purpose gear lube API rating GL 5 for severe duty operation; SAE 80 or 75W-90 below -10° F, SAE 90 or 80W-90 above -10° F, SAE 140 or 80W-140 above +90° F



Hope this helps out







(edit spelling)

 

[Dieselman359]

My 2 cents

Personally, I like to use both a gasket AND some blue RTV selant. I'm not to fond of leaks!

I also use 75w-90 Amsoil in the rear and have a Mag-Hytec cover which uses an o-ring instead of a gasket, which has stayed sealed up for about a year of two now. It also has the extra fluid capicity, and looks cool with the new flatbed

 

[Philip]

The 205 case is a gear drive case. I think any use of 4x4 puts it into the severe duty operation class. I do not trust motor oil holding up to the gear shear loads of 4x4 operation.



Let me explain this a little better. All of the big 3 mfg's spec 75/90 gear oil for a front/rear axle. The 205 has smaller and narrower gears in it than a axle assy has. Why put a lighter oil into something that has smaller gears. The smaller gears are in need of it more than a rear with gears that have 3 times the amount of wear surface.



P. S. I feel the same way about fluid for a manual trans.



All the above= IMHO.

 

[DPKetchum]

In four years at the Dodge store all i saw used was the red Mopar gasket sealant. Used for all diffs. from Jeeps to 1500 trucks,Diesels with limited slip etc. Never can think of a time anything leaked and some we serviced the covers had not been off in several years and 50,000 plus miles.

 

[sparks57]

The oil I got was at CarQuest and is Premium 80w90... is that OK? I'll try and find some gaskets, just to be safe.