Transmission fluid change

  • 3 POSTS
  • 6 CYL
  • 4WD
  • 125,600 MILES

Two years ago my inherited this vehicle with about 108,000 miles on it. Since then we have used the truck off and on since it serves as an additional recreational truck. The truck currently has about 126,000 miles. I have been wanting to change the transmission fluid to keep up with the basic maintenance since I am not sure when the last time it was changed.

I was told by friends and my trusted mechanic not to change the transmission oil since I have no history as to when it was last changed because the transmission will fail.

If I do change it, it is true that I run the risk of the transmission failing? This does not make sense to me, as I am simply changing old fluid with the new to preserve the integrity of the truck. Any thoughts or recommendations in how to proceed?

Do you
have the same problem?
Monday, June 19th, 2017 AT 12:16 PM

1 Reply

  • 29,775 POSTS

If someone tells you changing the fluid will cause damage, ask them to explain their reasoning. They may be thinking of a transmission flush service. There are mixed opinions on that. Changing the fluid and filter simply restores the worn-out additives and removes much of the varnish that has formed from the fluid being hot. Only about half of the old fluid drains out and needs to be replaced. The flush gets pretty aggressive and replaces one hundred percent of the fluid. A strong detergent is added first, then must be removed as part of the flush. Some of us feel that detergent can dissolve some of the friction material on the fiber clutch plates.

My limited experience from talking with people who have had flushes done is they were usually trying to solve a pre-existing problem, and when the flush did not solve it, and that problem became worse, they blamed the flush for the transmission's failure. In fact, the failure was likely going to happen anyway. My opinion is if there is no problem now, there is no value in having a flush service performed, and if there is a problem, a flush is not likely to solve it. If there is any slippage problem, that is due to wear of the clutch plates or a cracked or torn rubber lip seal in the clutch pack. Those are mechanical problems and a flush will never fix a mechanical problem. If the fluid and filter change is way overdue, varnish build-up in the valve body can prevent some of the shift valves from sliding smoothly and freely. That can result in delayed or late shifts. A flush, with that harsh detergent, may solve that, but given some time, the severity of that problem is likely to be reduced just from the new additives from a fluid and filter change.

Was this
Monday, June 19th, 2017 AT 10:37 PM

Please login or register to post a reply.

Recommended Guides