I'm going to be changing the fluids in my transmission (manual), transfer case, and both differentials. I was just wondering if there were any recommendations out there on what to use. Pennzoil Synchromesh and Royal Purple Synchromax are both options for the transmission but I wanted to know if the Royal Purple is worth it. It's more than twice the price as the Pennzoil per quart. Knowing I will only do this once every few years I'm just trying to decide if I can justify paying that much for Royal Purple. Is it really going to improve things that much?

As for the transfer case, the service manual recommends Dexron III ATF. Again, is Royal Purple worth it? There are a lot of different brands out there for this and don't really know much as far as one brand performing above another. Since the transfer case really isn't used a whole lot or exposed to a lot of heat I can't see it really mattering if it's the most expensive stuff or the cheapest. Seems to me both will be able to get the job done. So again, anyone recommend a certain product over others?

Pretty much the same question for the differentials. With this, is synthetic necessary? I could see using it in the rear since that is being used all the time but probably not necessary in the front since that is only used a fraction of the time. And again, any brand recommended? I know NAPA sells Valvoline and NAPA brand. I'm guessing even the NAPA brand would work fine. Then just replace the gaskets.

Basically the only reason I am considering the more expensive oils and fluids is because this is only something I will do every few years. The service manual recommends ~40k miles so that's probably 3 years for me. Spending a little more isn't a big deal when I know I will only have to do it once every three years. I might even be able to longer using better fluids. Just looking for some opinions out there.

Thanks in advance.

 

I don't think you can go wrong with the synthetic in the differentials, especially if you ever tow. The front does need attention too, it is always rotating when the truck is moving. I'm using M1. Don't forget the "limited slip" additive if you have one.

I don't have gaskets on my differentials, both use RTV.

For the NV3500 I've always stuck with the Mopar stuff. Yes it's pricey but I've had no problems and it shifts smooth.

Any good ATF +3 should be fine for the transfer case.

 

i used royal purple in my diffs, worked great, cant complain. and tcase and trans just use the mopar stuff.

 

I have never used Royal Purple, I use Pennzoil Synchromesh and change it every 48,000 miles. I have used the Mopar manual trans lube but I found my trans shifts much better and has a lot less noise with the Synchromesh. Plus Synchromesh costs half as much as Mopar MTL.

I use plain old Valvoline 75W90 gear oil in my differential, it does fine and I change it out every 12,000 miles. Valvoline only sells their 75W90 with the LSD additive now, they must have stopped selling regular 75W90. I don't have a LSD but I have had no problems at all with the LSD additive gear oil.

There is no need to buy any differential gaskets. I don't even think my truck had a differential gasket from the factory, just orange colored RTV, and lots of it. Permatex has a new sealant they just started selling about a year ago, it is made specifically to be used with differentials and gear oil:

http://www.permatex.com/products/Aut...tv_sealant.htm

Napa is the only place around here that sells it. The Dodge dealer will sell you a tube of Mopar differential sealant, it is probably the same thing but more expensive. I used to use the Mopar sealant before the Permatex differential sealant was available. I just scrape off the old sealant, clean both surfaces very well with a shop rag and solvent, clean it off with laquer thinner, then put the sealant on the differential side only, put the cover in place and bolt it all back up tight. Never had any leaks or problems with it.

I have no idea on the transfer case, my truck is a 2 wheel drive.

Jimmy

 

good to know

 

i used royal purple in everything i can engine and diffs then the tranny and transfer case i used schaffers fully synthetic atf pricey at about 9-10 bucks a quart

 

Purple has been good to me. Ive been going like 30K or so..but that is a lot due to time. I only have like 65K after about 8 yrs. Anyway, I would tell anyone Purple after looking at my gears after towing, driving and everything.

I use black permatex. Stock was a red sealant, i.e. no gasket.

Word of advice with the front diff; Practice putting it in. Pending your arms/hands (mine are fat) you can put the RTV on the case, not the cover, and youll be a lot better off.
For the front also, keep in mind, it spins all the time..its just not under power...so the oil is broken down like your rear.

As to brands; who the hell really knows? Im sure people have had rears or trans. explode on purple, and swear by dino oil. Its like tires, or any other subjective thing. I saw my old audi with over 100K miles, Mobil 1 used for its life. Crosshatching still on the cylinder walls. re-diculous. So, I was convinced. You won't go wrong with purple.

small FYI, the 'green' oils or others that are cheaper, are just recycled by the vendor and resold. Good theory, but know what you are buying...

 

All good information. Thanks guys. I've never really done a lot with differentials and transmissions so I wasn't sure if there was something way better than the rest. I'll probably use Pennzoil Synchromesh for the transmission. I know my NAPA has it and it's a lot cheaper than the Mopar or RP. As for the differentials probably Valvoline or NAPA (which is Valvoline) 75W90, depending upon how much more the synthetic is I might go that route but not sure. And then whatever ATF is not too expensive for the TC.

Of course this stuff always changes once I get in there and start looking. I never leave with what I went in for... I always end up with more or more expensive stuff