Transmission problem

I'm posting this here cause I always get answers here. I do own a Dodge truck, but right now it's running just fine.
Vehicle; 1980 LeBaron (149,000Km); 318 (49,000Km), A904 Tranie (71,500Km).
Generally the car runs great (after new rebuilt carb with ported vacuum, installed), no rust, no body damage, slight vibration over 80 Km, another problem for another day. Problem; Tranie has a hard time shifting from 1st to 2nd if the speed is increased gradually while going up a STEEP hill . It tries to shift but just rattles. If the throttle is increased it shifts OK, it just seems to do it at slow acceleration. On a flat road, or on a medium steep hill, at any rate of acceleration, it shifts fine, and you can barely notice the shift. During stop and go traffic (rush hour?) where the speed is up and down between 15 and 20 Km, the first dozen or so 1 to 2 transitions are smooth then it starts to get progressively harsher. City driving (stop light to stop light) is fine, no problems. Towing a trailer with 3/4 yard of redimix cement had no problems (last summer, about 15 Km on flat roads)
I've recently replaced the filter and fluid There was some sediment on the pan and magnet, but nothing I haven't seem before, on other tranies. The problem wasn't evident before the fluid change, but then it wasn't used in rush hour or on steep hills. The current and the old fluid smells OK, but looks like blood (murky red). Used Dexron 3 with Mercon, couldn't find just Dexron. Yes I checked the level of the fluid and it is almost at the max mark on the dipstick. So now the question. Is there an adjustment that needs to be done or is this a tranie rebuild, again?
Had a 68 Dart (in the 70's) with a 273 V8, same problem. After taking it to a tranie shop for a free tare down and inspection, then refusing the repair (they had to reassembly the tranie and give me the car back, in running condition, free), it never skipped again, up to when I sold it 18 months later. They never told me what they did.
Thanks in advance
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Adjust the bands, particularly the front band. tighten the adjuster (found on the drivers side above the shift levers) to 72 in lbs, and back off 2.5 turns. THere is a lock nut, so treat it accordingly.
If that doesn't do it, you may need to rebuild the trans. Likely cause of the problem is simply old age. Sitting as much as it must, will kill a vehicle as much as using it.
--
Max

"There are four boxes to be used in defense of liberty:
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks Max, for the help, I'll give it a try.
Kinda expected problems from long storage (8 years in a barn, not started). The owner had to replace the engine cause the block cracked. Drove it for a few more years, then got too old to drive, and parked it again, I got it a few years ago. It was an estate clearance, and the deal was too good to pass up (or maybe not).

(71,500Km).
another
to
it
Km,
get
OK,
it
repair
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.