OK, here's something new gone wrong.

88 S-10 4x4 4.3 automatic (I'm assuming 4L60, can't tell for sure 'cos the glove box door is not original). When I first start it up and put it in gear, it gets stuck in first, not wanting to upshift; sometimes this shift from P also feels like being kicked in the seat of the pants if I don't wait until the engine goes to low idle. After a minute or so of driving, I get second gear, but the shift is also rather abrupt, and doesn't happen until at least 2500 RPM. Then I have only first and second until the truck is completely warmed up, at which time I get third, fourth and finally lockup as normal.

The vehicle has 215,600 miles on what I'm assuming is the original transmission, at least I haven't replaced it in the 16+ years I've owned it. Fluid is full (maybe even a little over), and nice and red, doesn't smell burned. Had a few little bubbles in it, not too frothy.

I've searched some of the threads on here, and most of the problems listed were with the 4L60E, which this isn't likely to be on an '88. Also the postings about this were mostly saying that it got worse, not better, as the thing warms up.

I just replaced the TPS a few months ago (probably didn't need to, but whatever), and the speedometer works, albeit a little wibbly, so probably not VSS either (if this car even has one, it might just be a straight speedo cable on a vehicle this old).

(Couple days later, the brakes went out, halfway to work. Not fun driving 40 miles there and 65 miles home with no brakes. Mechanic said the brake lines were rusted out in the back; he replaced those, bled everything, and the brakes work again. Almost certainly not a related problem, just mentioning it b/c it happened around the same time, and he couldn't diagnose the tranny because he was afraid to drive without brakes, not that I can blame him.)

Coincidentally the vacuum reservoir ball collapsed, creating a massive vacuum leak, at the same time as the tranny started acting up, but when I closed that off, and subsequently when I put a new ball on, it hasn't made any difference, so that's probably unrelated too; besides which my mechanic tells me there's nothing vacuum-controlled on this tranny anyway.

Probably unrelated is that the middle crossmember is busted at the left side bracket; that's been like that for 8 years now, so it's not likely to be anything to do with this. I was just getting around to fixing it ($286) when this happened.

Any suggestions as to what might be wrong?

Thanks, in advance.

 

Sounds almost like your governor is sticking when cold. It is located on the driver side near the back of the transmission. It will be under a little sheetmetal domed cover.

THIS ARTICLE shows the location as well as the process for calibrating it for different shift timing.

 

You have the 700R4,4L60,4L60e tranny, there are some disfferences over the years, hence the name change. The most common change is from trottle cable shifting to electronic shifting in '93.

Yours is a 700R4. And Kyles analysis is a great place to start. I memory serves me correctly, I do believe the governor controls downshifting though.

If this is a 4x4, you will have to pull t-case shift linkage to get the governor cover off. When you pull the governor out, make sure the gears aren't cracked, or teeth arent missing, find them. Also make sure the butterfly's open smoothly and they arent bent. You will need new pins if you take it apart, no nails wont work.

Almost sounds like your trottle valve is out of adjustment. There is a "button" located on the engine for adjustment.
Rather than recreate the wheel, http://www.tciauto.com/Products/Inst...ble_adjust.htm

Theres videos too, google GM TV Cable adjustment.

If the adjustment doesnt fix the problem, the issue could be witht eh TV itself, the trottle vavle (tv) is located int eh valve body and you have to take the valve body out to access it. This is a job for more experienced DIY, or Pros only. There are check ***** that need to go back into their proper place, and you may have to replace the paper. A common mod when rebuilding the tranny is to place a spring behind the tv, this pushes the tv back out, rather than waiting on fluid flow to do it. Most rebuild kits include the spring.

 

Henr3, I don't think I'm up to doing that level of work myself. I looked up adjusting the TV cable, and I think I could handle it, but I'm not pulling the governor; if that needs doing, a mechanic is going to have to do it.

So I was at the dealership the other day and saw they were advertising a transmission power flush, like what we did for the cooling system on the '99, for something like $240. Asked them about that, they said they wouldn't do it on a transmission with 215K miles on it, they're more likely to break something else.

Took it to a transmission specialist. (Not a chain, this is an independent guy (http://www.lorengstrans.com/). I was impressed with his shop; among other things he had a huge-*** clamp on the side of his workbench that held an entire transmission, and let him swivel it to any position in case he wanted to work on the underside of it.) He drove it around with me in the passenger seat. Worked perfectly while I was there, even though it wasn't behaving on the way. He suggested I bring it for a tranny service ($99) which involves dropping the pan, and see if there's any debris floating around in there. I was going to make an appointment for later this week, but this morning it's working perfectly again. Whatever was busted seems to have magically fixed itself. Goes smoothly into drive, shifts right away, everything works.

I hate intermittent faults.

What do I do now? Should I still do the service as a preventive maintenance item, or invoke Tomcat's Law ("if the damn thing works, leave it alone")?

 

I would probably say it would be a good idea to go ahead and do as a preventive maintenance.

 

Just as a follow-up, it's now a half a year later and it's still working. Wish I had the magic like that, to fix a car just by looking at it.