Hard shifts

Maintenance/Repairs
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1

My 2005 VW Jetta sometimes slips between 1st and 2nd gear.- Maybe once every 150 times I go out. There is no indicator light on the dash and no codes show up on the dealer’s computer, so they won’t look inside the car’s transmission. They tell me it may be the fuel mixture, which may change from season to season. But I have my doubts. Should I trade this car in before the warranty expires, or is there a reasonable way to fix this for good?

2

This is an automatic? When you say “slips between 1st and 2nd”, what exactly happens? This is going from 1st to 2nd, vice-versa, or both? Is the “slip” that it shifts out of 1st, the engine revs, and then goes into 2nd? I can’t imagine what the fuel mixture would have to do with this – it sounds like the dealer is trying to avoid doing potentially expensive warranty work on the tranny. Make sure you’ve got the problem description in writing so that they can’t legally stiff you after the warranty has expired.

3

Automatic transmission, but when it happens, it feels like an standard being driven by a teenager just learning how to shift into second gear.

4 
I don't buy the fuel excuse.  That is worse than my dog ate my homework.  

How about a really good description of that shifting.  I taught two teenagers to drive shift and they both did great so your description does not help me.   Is there a jolt or does it slip a lot or what?
5

Engine revs up then hard jolt into second gear. But not all the time, only once in a great while.

6

this could be a transmission problem with shift solenoids (dirty and delay shifting from lack of pressure build up), or possible bad 2nd gear clutch packs (theu do the most shifting of all in the tranny and usually are the first to go, especially if driven hard or manually shifted…or have you checked the fluid level, color, odor, when last changed, was the CORRECT ATF used? Some imports are pretty sensitive to the friction modifiers that are used…like Hondas. This should be diagnosed with pressure testing, alignment and checking of the motor and tranny mounts (often overlooked)