I changed the tranny and diff fluid at about 8500 miles to get rid of the break-in fluid. I know, I should've done it a lot sooner, but I didn't. Now, I have 27,600 miles on the truck. About 65-75% of that has been towing (usually I have a car on my trailer). I have a busy summer coming up with a whole lot of towing. I was thinking of changing my tranny and diff fluid now both because it's been close to 20,000 miles since last time, and because I have a lot of miles this summer coming up. I'm wondering, about how long should I wait between changing these fluids? I want to keep my tranny and diff very happy for long periods of time, and I also know that summer is the biggest stress on these components.

Also, I use Mopar fluids in these. For the tranny I use 75W-140 as per the TSB that said to use 75W-140 instead of 75W-90 if you did lots of heavy towing.

Thanks!

 

I don't think you have anything to worry about. You should be fine.

I plan to do my diffs, transfer case and auto tranny fluid every 15k. I just did it the first time at 15k, and now have about 18k on the truck.

 

Ted,
I hope you didn't use 75w-140 in the tranny!

I'm sticking with the 15k service intervals for both the tranny and diff.

MikeyB

 

No, it's Mopar 75W-140 in the diff, and then the Mopar special synthetic tranny fluid in the tranny.

Ok, since 15k seems to be the consensus then I'm 4k overdue and will change both this weekend, along with the air and fuel filters. Thanks!