I have a 1996 Bronco with a manual transmission. The only fluids I've changed since I've owned my truck are the motor oil (on a regular basis) and power steering fluid. I have been reading up on transmission and differential fluid changes and have run into a couple questions.

First of all, I am not quite sure what transmission my truck has. I believe it is an M5OD, but don't know for sure. The transmission was brand new when I bought it (had been replaced at 100k) but I assume it was replaced with the stock transmission for my truck. I have now put 80k miles on the transmission and feel like its a good time for a fluid change.

The thing is, I don't know how much fluid I need for a fluid change. If what I read is correct, all I have to do is remove the drain and fill plug, then replace the drain plug and fill the fluid back in. It should take about 5 quarts of ATF. Is this correct? And can I add synthetic fluid if I do this method with something like Royal Purple or Mobile 1? I'm just confused because I also read doing a total transmission fluid change involves like 15 quarts, and if that is the case, then I probably shouldn't mix fluid types.

 

15qts would be for an automatic transmission.

 

M5R2 (M5OD) fluid capacity is 3.8 US quarts and its picky about that amount. Redline MTL (Manual Trans Lube) or Synthetic ATF is best in the M5 as the unit relies heavily on splash to keep the upper bearings lubricated. Heavy gear oil is NOT recommended as it tends to make the synchros sluggish and shifting difficult especially in the cold.

 

Okay that's what I thought. I have had a terrible headache all day so I've been a little out of it when looking this up. So all I need to do with my transmission is pull the drain plug then put the new fluid in afterwards? And I can switch from mecron II or whatever is in it now to a synthetic ATF like royal purple?

 

Thanks Greystreak! Like everyone says, you're always extremely helpful. Over the years of searching these forums your knowledge has helped out so much thanks again!

I'll probably get around to changing the fluid Friday. I didn't realize how expensive the synthetic fluid is.. like $15-20 per quart so I'm going to wait to get a little more money. I still have (okay want) to change both differentials fluid with synthetic too and maybe the transfer case also.. I wish the fluid was as cheap as normal motor oil! Oh well I'll wait to get some money from the Air Force this Friday so I can get gas and oil!

 

Don't waste synthetic oil on the differentials (the mineral gear oil runs 100k miles without issues in there under normal conditions, and if you do any deep fording you'll need to replace it anyway), use synthetic in the transmision.

 

Agreed! Unless you are doing serious racing or crawling, the regular heavy weight oil will perform just fine in the diffs.

 

Alright thanks, I won't use synthetic in the differentials then. My trucks a daily driver so I don't do too intense crawling or mudding or anything. If there was water and mud here in Arizona maybe I'd do it a little more but it's hard to come by!