gearhead0777

Hey guys, well the trucks been bucking like a bronco at cruise speeds so, I figured it was the transmission. I decided to start by changing the fluid and filter, so when I dropped the pan I was intrigued to find a fairly large plastic piece, that looks importantish floating in the fluid. Could really use an assesment on what it could possible be. i will hold putting everything back together until I get a response.

gearhead0777

Nevermind guys, I googled and found that thas just a factory left over part. But since i opened the thread, does anyone know what could be causing the bucking? It is in the middle of the gear ratio.

aliens8mycow

We might have the same issue - I have almost the same truck - 91 2wd 302 automatic. It's been bucking and chugging for awhile now. I've chased down all the codes from the computer, replaced emissions parts as needed, and it's still bucking.

I'm about ready to take mine to a tranny shop too. I'm not getting any computer codes related to the tranny, but I don't know what else to point toward.

If you take yours to a shop, please post results so we'll know if it helped or not.

gearhead0777

Will do, mine is throwing codes, a lean engine mix code, which dont where its coming form but dont think it has to do with 60 MPH Lurching. and a TPS code which it has thrown since th day ive owned it, so both are unhelpful. Ive got the fuid back in it, hoping this will help resolve the problem :-/

Just call me Sean

iTrader: (1)

You shouldn't be getting a TPS code unless there is a problem. It could be out of adjustment or faulty. Test it to see if it's operating correctly. Aliens8mycow just unplugged his oxygen sensor and got the lean code and transmission issues, so you both should look into a new oxygen sensor.

aliens8mycow

I've been trying to do the o2 sensor all day...

Another tidbit for you on the tps - if you have a volt meter, you can check/set it accurately:

Unplug the IAC valve (driver's side of the throttle body) and start the truck. If the idle rpm isn't right, get the idle set where you want it by adjusting the stop screw on the throttle plate above the manifold (where the throttle cable connects). There's a sticker that says to never turn the screw, but if you're not the original owner, it could have been turned. (mine was, with pliers from the looks of the screw head...)

Turn the truck off, and don't forget to plug the IAC back in. Turn the ignition on, with the engine off. As you look at the pigtail for the tps from the front of the truck, check voltage between the center and left wire - perfect voltage is 0.98v. I think the range is .66 to 1.22 or something like that, but supposedly 0.98 is right on the mark. You can tweak the voltage by turning the tps either way (one way raises voltage, the other way lowers it).

Brad57

If you get a dead spot on your tps it will cause a buck when the throttle hits the dead spot so its usually noticed when cruising unfortunatley you cant find a dead spot with a multimeter since they dont have a very fast update speed but if you can get an ocilliscope its very easy just do sweep with key on engine off have someone use the throttle pedal and slowly push it to the floor and let off you will see the dead spot on the pattern

gearhead0777

Ok, well sometime this week I will go out and get both sensors and put them on and see if this helps, truck is happy with the new fluid though, noticeably different shifting.