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98 GMC Jimmy auto transmission

I posted this sometime ago, but unable to find it in the discussion log… I have this vehicle, 4X4 SLE, that for the past 30K miles when going into the 2nd gear it would buck & sometimes I would feel alittle pop, however, if I let up on the accelorator pedal during the shift there is hardly a buck at all. Someone replied to my message about taking it & have the computer checked for codes- I havent done that yet, HOWEVER, I have noticed since switching to Premium gas (was using Mid-grade b4) that the bucking has almost completely stopped altogether. I have 92 Ford Ranger 4X4 that I can only use premium gas in otherwise I get severe knocking. Whats the dif on using higher grade gas that stopped my trans from bucking?

Ok, so I had an auto parts store check for codes, it came back with - Zero codes available… so what do I check next?, the parts guy suggested taking it to a transmission shop for a computer diagnose, I have never in my 40 years of driving had transmission problems- do trans shop offer such a thing? and if so what is the reasonable charge for that? And whats the best way of finding a reliable, responsible transmission shop?

Why do you believe it is the transmission?

Joseph, I agree with you.

tcorrell, if premium fuel is eliminating your problem, then chances are the problem is engine related. The higher octane is preventing pre-ignition (knocking, pinging, dieseling) from happening. This is generally a sign of carbon fouling in the combustion chambers. Both of these trucks were designed to use regular fuel, so they should run great on it. Tester posted this link for seafoam earlier this year. IT can help you clear this up.

I ran this vehicle on mid grade gas for over 6 years, I only switched to premium recently within the past two months, (and I regularly put injection cleaner fluid in the gas tank in all the years I have owned it)…because I know how my Ford truck runs better premium and so I thought I would give it a try, and to my surprise the bucking almost completely stopped---- I said, ALMOST- read my orig blog, it didnt completely go away but it has soften it so dramatically that it does pain me when I know I am getting to that gear…