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1998 suburban with a 5.7 having trouble shifting up, it just revs up but never shifts, backfires occurring often when revving up too. If anyone knows what could be the most likely cause I'd really appreciate the help.
 

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Does it go into 1st and not shift or stay in neutral?

Can you get into reverse?

Backfire shouldn't have anything to do with shifting. That's another issue.......
 

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Does it go into 1st and not shift or stay in neutral?

Can you get into reverse?

Backfire shouldn't have anything to do with shifting. That's another issue.......
It does go into 1st, but then it doesn't get out of that, not often at least, some times you can get it to second by over revving and then letting go of the pedal, it will shift into reverse no problem too.
 

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My guess, and I'll let others chime in, that the issue is in the Valve body. There a a couple of accumulators that can go bad that control shifting, or it could be elsewhere in the Valve Body. There are check balls that can jam and a couple other areas.

If it is the VB, not a huge job, but requires the transmission pan to be removed. I rebuilt the VB on my 99 a couple of years back and it was pretty straightforward an dnot a lot of $$. Or you could just buy a rebuilt VB and put it on.

It is possible its elsewhere in the tranny, so see what other suggestions you get.
 

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You say that it will engage in first gear, but never upshift? Does that mean it will move? Will it upshift into 2 if you manually put the selector into 2 (this vintage vehicle, selector in 2 is supposed to force the transmission to run in 2 no matter what)? Is the speedometer responsive when it moves?

I encountered a case of "runs in 1st but won't upshift" when I lost a transmission speed sensor (it was accompanied by a transmission speed sensor code and abs speed sensor codes). You can read about the adventure here: Another road trip, another adventure. You haven't described any of the accompanying symptoms that I experienced, so maybe you are not experiencing the same issue, but maybe it will give you some additional ideas.
 

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Which transmission? 4l60e? Probably
But not if this is a c/k2500..... Do you have a check engine light? What codes are present? Can you see the prndl indicator? Are you sure its 1st and not 3rd? Blow a tranny fuse? Tell us ALL of the details.... if no codes it could be the tps, throttle position sensor or you need a rebuild. You can test the tps with any good scanner, in graph form there should not be any breaks, jumps or missing data as you open the throttle, the graph should simply rise smoothly. Hell a tps is only 30 bucks and takes a couple minutes to change, but test it first!

Al
 
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Which transmission? 4l60e? Probably
But not if this is a c/k2500..... Do you have a check engine light? What codes are present? Can you see the prndl indicator? Are you sure its 1st and not 3rd? Blow a tranny fuse? Tell us ALL of the details.... if no codes it could be the tps, throttle position sensor or you need a rebuild. You can test the tps with any good scanner, in graph form there should not be any breaks, jumps or missing data as you open the throttle, the graph should simply rise smoothly. Hell a tps is only 30 bucks and takes a couple minutes to change, but test it first!

Al
 

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Well, it's nice to see we dont have full access to delete our own threads. That's PHUCKING BS.
 
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How many miles or on this trans. If its the OE trans, its most likely time for a reman. Between 225,000 to 275,000-300,000 miles is about all the life you will get out of an OE 4L60E trans. A decent trans shop, should be able to do a reman for maybe $2000.
 
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Oh, and as for doing the work your self, well, been there, done that, and its something that I will pay to have done for me. A ling time ago, I did a reman on a Ford C-4 trans. It didnt make 150 miles, before it went out again. Its just something that takes special tools, knowledge and a very clean enveroment to do the job seccessfully. Most of this, your average guy just doesnt have, unless you do trans work.
 
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