Want to flush my trans and all my differentials w/ synthetic fluids.. help?
 

Hello all. I want to flush my transmission and rear and front differential, and wish to add synthetic fluid to them when filling them back up. What are the best options in regards to this? I'm a huge synthetic fan so please, no trying to ask my justifications.

Thank you,

Matt

Not to sound like a broken CD, but search and you shall find the answers. Rear Diff is an easy drain and fill. There is no front diff--but a transfer case. This is not so easy of a job as you can not gain access to the fill plug on the top. You have to fill it through the drain plug on the bottom--that is the problem. You either need to get the car up 2 feet on one side or use a check valve set up to get the fluid back in. The Jatco tranny is also a touchy one! Supposed to be super sensative the correct fluid and goes for big bucks from Jag.

Why do you want to do all that.....they are FILLED FOR LIFE/NO MAINTINENCE required right from the Factory. (That is a joke!)

What brands and models of synthetic fluid should I put in there? I can handle the rear diff I think, but as you stated the transfer case might be too much for me. Might take that one in to get done. Any additives that are required or recommended to put in any of the items?

Some dealers including mine, are now using a BG transmission flush/conditioning and refill system using a perfectly compatible BG synthetic ATF (guaranteed for any faults after this service ($300.00)..The Transfer case and Rear Differential you can use Any good quality Synthetic gear lube (75w140)..Redline, Castrol, Royal Purple, they all meet or exceed the specs. (I used Royal Purple as it has healing properties as well)

good info.. thank you for much!

The diffs dont need any friction modifier or anything? Just straight gear lube?

85_305, for the transfer case, it is easier than you think. I have done the fluid change on my car and what I used was a radiator drain plug that has a collar on the T-handle. This allows you to insert a tygon tube into the collar and refill the system that way. Then you simply let the lube gravity fill into the transfer case. All you need is a male 1/2" NPT to female 1/4" NPT fitting. This can be had at any hardware store for like $3. The radiator drain plug can be had at any auto parts store for around $5. The tygon tubing is like $5 for the appropriate size. To get the fluid from the quart bottle to the tygon tubing, you can either cut the tip off of the nozzle that comes with the bottle and then stick the tygon tubing on to the end (this also allows you to force feed the fluid in, but, can be a bit more messy as you have to pull the bottle off of the tygon to let the bottle refill with some air) or you can take a funnel and feel the tygon through it a little bit, put some masking tape on the end of the funnel so that the tape causes the tygon to flare slightly and then pull the tube back into the funnel. This will form a seal and you can dump in the necessary amount that way.

As for the rear differential and transfer case, they require 75W-140 full synthetic fluid. I personally use Mobil 1. No need for any additives of any sort to either of these cases.

If you need more clarity to doing this, let me know. It sounds more difficult than what it really is.

Excellent explanation! Thank you very much Thermo. I'll probably use either mobile or lucas synthetic gear oil then. Much appreciated!

Hey thermo. How much gear lube are we talkin about here? Is it 600ml for the transfer case? And how much for the diff? Thanks

Silvercat, the transfer case requires 600ml of 75W-140 full synthetic gear lube if the case is rebuilt and all the internals are dry. Other members have reported that unless you jack the passenger side of the car up to get the last little bit out of the transfer case, you will leave behind about 200 ml of gear lube. So, putting back in about 400 ml of gear lube should be what you shoot for. You can put in up to 600 ml without any major issues. You may notice a little bit of gear lube draining out behind the right front tire from the transfer case vent spitting out a bit of fluid. This fluid can land on the exhaust pipe and cause a little bit of smoke/acrid smell.

As for the rear differential, the capacity is 1.2 liters, or just over 1 quart. So, if you do both the transfer case and rear differential, you will have enough fluid for doing the rear differential once and the transfer case twice. Personally, I am going on a 30K mile transfer case fluid swap. Overkill, some might say so. Prevent possible transfer case issues, I'm doing all that I can to not have them. 600 ml of gear lube isn't much for something that is handling the full power of the motor. As is mentioned in other posts, the transfer case is "filled for life". YEAH RIGHT!!!!!!

Excellent info. I'll be doing this in a few weeks

Excellent thermo, thanks i have to get on that mine sounds like it needs it. I also tried to get the kit from wild bill but didnt get response im gonna have to make my own...

SilverCat, making your own isn't hard. If you use the method I did, the big trick is finding the radiator drain valve with the collar on it. If you don't know what I am talking about, most of the radiator drain valves will have a T-handle at the very top. A select few will have what appears to be a spent gun shell casing sitting on the T-handle. You want the gun shell one.

The other "trick" is getting the tygon on the valve. The trick I use is this: the T-handle moves away from and closer to the valve based on it being open or shut. You want to get the T-handle as close to the body as possible then attempt to put on the tygon. That extra 1/4" of space makes a world of a difference. Also, the use of needlenose pliers is handy too. Just can't squeeze too hard else you will never get the tygon in the hole as it is a pretty tight fit and if you oblong the tygon, you then have to use your finger to push it into place.