1995 lumina bucks

1995 lumina car 3.1 bucks in overdrive
I am puzzeled to what would make my car buck,or miss at high speeds ,pulling a gradual hill and when its warm ,wont do it when its cold,have put new plug wires in and plugs ,i just put this reman engine in and this problem exsisted with the old motor ,one mechanic told me it might be the tcc solenoid,also no codes or check engine light if i increase speed it will eventually go away.also in drive it seems to not be happening,other than this issue car runs good and idles like a kitten. anyone have any thoughts?
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if it normally happens at 45-55mph, the TCC solenoid is the issue. It's not disengaging teh lock-up and the engine is lugging trying to accelerate

My '95 van also bucks but not at those speeds in particular, more like when ever it has accelerated to a cruising speed. Goes away if more gas is applied or if foot is removed from gas. Doesn't do it while using cruise control on the freeway.

Same cause? or does mine sound like trans-axle as I have feared?

btw, what and where is the TCC solenoid?

The TCC solenoid is an electronic valve that controls torque converter lock-up. It is located in the valve body, and only operates when the engine is warmed up and you reach a steady cruise speed. It's main purpose is to reduce heat build up in the trans and increase fuel economy by eliminating torque converter slippage. When they fail, the symptoms will be similar to trying to accelerate a stick shift car from too low a speed for the gear you're in without using the clutch.

That sounds like me too. I'll have to look that one up in the manuals.

Thanks again Rich

I couldn't find anything in the manuals about TCC solenoid. Might it be under another name? Could it be the component screwed into the housing with an electrical connector? Front side of the tranny?

My 95-3.1 had the same problem, bucked at around 45-55 on slight grade and would buck at 70-75 in cruise when starting up a slight grade. I was going to change out the TCC solenoid but found out it's really a major job for a shadetree mechanic, so I figured I'd just change the tranny filter and fluid. I changed the filter and filled up the tranny with same amount of fluid that I drained (yes I know there is more than 6 quarts in the tranny) and then I put in a quart of Lucas and after about 300 miles of driving, the chuggle/buck went away. So far, so good . I think probaby the combination of clean fluid and the Lucas has "unstuck" the TCC and the tranny is running cooler as well...worth a try before you commit to major surgery...