I did a search for the problem I am having and i haven't found one doing the same thing so here it is. I had been out all day driving here and there, so when I am almost home I notice the tranny shifting hard into 2nd. It does it the whole way home just in second but then I put it in reverse and shifts hard when I put it in gear. Then when I put it in drive shifts hard like the truck wants to go but I have my foot on the brake. Anyone seen this before. Truck was warm been running all day and problem just popped up.

 

I did a quick search,this applies to you
https://www.performancetrucks.net/fo...hlight=po+1870

If you dont run it very long you maybe able to save your trans with a valvebody repair.Shops and dealer see this all the time and sell uninformed customers complete rebuilds,dealers will want to replace valve bodys to correct this problem ,independent shops can fix the valvebody with a transgo shift kit or a sonnex repair kit that bores the VB for a new valve.The truth of the matter is it can be fixed with the correct single $2.00 spring.How many miles on this unit?Can you do your own work or will you pay someone?

 

James b. is a self taught trans guru
https://www.performancetrucks.net/fo...d.php?t=352201

 

The truck only has 45k on it. I have done alot of basic engine work but never messed with a tranny. So most likely I will have to pay to get it done.

 

I have seen this problem on dodge trans, it was a problem with check ball in the valve body. sounds to me like valve body related.