OK... A little backstory. I have a 2000 4dr 4WD Blazer. At 55000 miles, I noticed it slipping from 1-2 with a hard shift after driving at high speed for about 30 minutes and then coming to a light. After about a month with it becoming more and more common, I wised up and took it to a shop. Burned up torque converter and new transmission was the diagnosis. $2000 later..... I continued to drive it with the rebuilt tranny until 114000 miles. When I lost Reverse (bad sunshell I think). Took it to a different shop (the first shop was now closed down). Well I found out why the first shop was closed down. It looks like he only replaced half the gears during the rebuild. Sunshell not being one of them. Another $2000 out of my pocket for a refurbed tranny (I wanted the old one just out of there), and refurbed torque converter.

So..... This past weekend at 124500 miles, after driving on the highway for an hour I come to a light.... Sure enough, hard shift from 1-2 and it happened all the way home for the next 20 minutes. I had the engine CPU checked and was getting a P1870 code as expected, so I took it back to the 2nd shop since the tranny has a warranty for another 1500 miles and/or 6 months.

He just called me and said after running it for an hour he can't get it to slip (I believe him, I haven't gotten it to happen since the trip this weekend), he did see the code though so he believes me. He has cleared the code out, and wants me to drive it and keep an eye out for it. And if it happens again, take it to the shop while they're open.

Here's where I'm concerned though. What if it doesn't happen again for 5000 miles and then my tranny is burned up again, and then I have no warranty.... Is there anyway to make this happen again, or testing I can do? I'm thinking I'm going to need to drive it for an hour during work hours and hope I can get it to happen...

Any other way I can force it to fail?

 

Just bumping this for one more shot at a response. Thanks in advance gang!

 

Well.... my 1 to 2 shift is like the recoil of a rifle. If I baby her off the line, i get to about 3200-3500 rpms before jerking into second gear and dropping down about 500-800 rpms.
on the other hand, if i stomp on it and go for broke, i can get it up to about 4500-5200 before it shifts and it shifts like a punch in the face. BUT with out missing a beat, it drops into 2nd gear right about the 3rd gear rev mark because i sit in second for maybe 1 scond and there is a slightly less stiff shift to 3rd and a noticable drop in rpm but not power or speed.
This transmission was rebuilt about 20k miles ago. when i bouth this thing 17k miles ago, it shifted like this. i was concerned at first, but since have had it broken a number of time and each time it is repaired, the test drive comes back normal. i have been in the truck when test driving on occasion, and it shifts rough, but has never been an issue. when addressed, the repair folk in question are not concerned by it.

i know that doesn't shed any light on your situation, but it has been 5 days since first posted and no one chimed in. I'm here to let you know you are not alone.

BTW: i hard shift wether cold/hot/dry/wet etc. it's just one of my baby's quirks i guess