5EAT on 05 LGT acting weird when cold

So my car is 05 LGT with 148K miles, i assume it is original tranny, short block rebuild was done 1500 miles ago. Car is completely stock

Had drain and fill done 1500 miles ago as well.

Issue #1: When cold, tranny will shift harsh between gears especially from 1-2 and 2-3. After warm up can't feel how it shifts, super smooth.

Issue#2: Cold or HOT it will vibrate in gear, it is more pronounced on incline and when in D or R or manual. In neutral it is fine

Issue#3: Tried to hold brakes and give it some gas, as i heard it is suppose to build boost and climb to 2500-3000 rpm, mine will be at 1800 RPM and when i release brake pedal nothing happens, still can't launch it faster.

Issue #4: Going down step hill in manual 3rd or 4th 5th speed will not stay stable it will increase, i heard about coasting clutch in 5EAT, and don't know how to check it if it is bad or what

Talked to my tech at subaru dealership, the guy who did rebuild on my shortblock. He says everything is fine, but it is bothering me big time, i drive it every day.

Fluid levels when cold are fine, when HOT it is slightly below the middle of upper marks.

Please help me out to diagnose those issues, i know there is something wrong or got missed during rebuild of my engine.

thanks a bunch

Issue #1: Normal when cold, especially in winter. I don't generally get 5th gear unless the temp is above freezing or the ATF is up to its required temp. Just take it easy for a couple miles.

Issue #2: Check ATF and front and rear diff fluid levels. When at operating temp, ATF is best when at, or the tiniest bit below, the full mark on dipstick. Low is bad, so is over full. Front diff has a dipstick. Rear diff is trickier. Pull the fill plug and add fluid slowly until it trickles out. A pump or a giant syringe will help.

Issue #3: If you have an un-modded center diff, don't do this past about 2000 rpm. You risk blowing up some tiny little needle bearings and destroying the diff. Even with that the car should squat and come off the line pretty quick. If you've 'bulletproof'ed the diff (look it up), you can sit on the throttle some more and when boost really starts to come on the revs will climb fast. Release the brake pedal and you'll be rewarded with a squeal, 3 or 4 short black marks, and a nice launch. Be prepared to change gears (you are in manual mode for this, right?).

Issue #4: How steep? I drive down an escarpment every day and it takes a pretty steep hill for the car to accelerate while coasting in gear, especially in 3rd or 4th. With the miles on your trans, it does sound like you might have some typical wear. Find a reputable trans shop to do an assessment.

The only thing they likely missed during the engine rebuild is that your trans is over 40k miles past the point where many people start seeing signs of wear. Just have another qualified tech look at it and go from there.

Issue #1: Normal when cold, especially in winter. I don't generally get 5th gear unless the temp is above freezing or the ATF is up to its required temp. Just take it easy for a couple miles.

 

Issue #2: Check ATF and front and rear diff fluid levels. When at operating temp, ATF is best when at, or the tiniest bit below, the full mark on dipstick. Low is bad, so is over full. Front diff has a dipstick. Rear diff is trickier. Pull the fill plug and add fluid slowly until it trickles out. A pump or a giant syringe will help.

 

Issue #3: If you have an un-modded center diff, don't do this past about 2000 rpm. You risk blowing up some tiny little needle bearings and destroying the diff. Even with that the car should squat and come off the line pretty quick. If you've 'bulletproof'ed the diff (look it up), you can sit on the throttle some more and when boost really starts to come on the revs will climb fast. Release the brake pedal and you'll be rewarded with a squeal, 3 or 4 short black marks, and a nice launch. Be prepared to change gears (you are in manual mode for this, right?).

 

Issue #4: How steep? I drive down an escarpment every day and it takes a pretty steep hill for the car to accelerate while coasting in gear, especially in 3rd or 4th. With the miles on your trans, it does sound like you might have some typical wear. Find a reputable trans shop to do an assessment.

 

The only thing they likely missed during the engine rebuild is that your trans is over 40k miles past the point where many people start seeing signs of wear. Just have another qualified tech look at it and go from there.

Wow, seems like you know what you talking about. I'll try all, that you said. What about fully draining trannsmission and refiling it with fresh fluids ? And another thing is how to diagnose if my CV Axles are the root of my vibrations ?? Thanks

If your fluid is still bright red and see-through, then you aren't likely to see any difference with a fluid change. Dark red, dirty, brown or muddy, then maybe. But condition isn't as important as level.

Get under the car and grab the shaft of a CV axle. Try to twist it. It shouldn't move unless the wheel is moving with it (which should only happen if you have an end of the car off the ground). Now try to move the shaft side to side (toward the wheel and away). It should move a little, but not be loose. Make sure the inboard end is fully seated in the trans or diff. And check where the boot meets the shaft. Is it wet? Leaky boots may not indicate a problem right now, but chances are the axle is on the way out. Best to mention it when you have the trans checked out so the tech can check those, too.