99 1500 Trany

My transmission has suddenly began to shift roughly from 1st to 2nd and then slips badly in 2nd and 3rd. Motor revs but not much power to the wheels.
I've been given the opinion by a friend who's a knowledgeable mechanic regarding motors etc, but not so much automatic trannys. Since this happened suddenly he feels a band adjustment wouldn't help and that it's more likely to be a seal. Sound reasonable?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

First, the dumb questions... fluid level good? How long ago was the last fluid/filter change?
If the fluid is full, I'd suspect the rear clutch is slipping... the higher you go in gear, the worse it gets (less mechanical advantage means more load on the drive side - same reason a worn clutch in a standard manifests itself in the higher gears first).

Slippage in 3rd indicates it's not as simple as a band adjustment (front band only used in 2nd). It could be a seal that's causing a drop in hydraulic pressure, which could be the root cause of the clutch slippage (as opposed to just worn-out clutches - which is also a possibility). This can be checked with a hydraulic test (requires hooking up pressure gauges to the various test ports, running the vehicle on jackstands, and measuring the pressure), but the reality of it is, you're most likely looking at a replacement/rebuild.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Fluid level is good and was last changed about a year ago including a complete flush. Only about 20,000 km /12,000 miles since.

OK. thanks. I was assuming that, but hoping for a miracle.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.