Transmission and Battery

Here's a first step diagnostic for shifting problems.

We replaced the transmission on our '98 Winny (at 141,000 miles) and have had it back in the shop twice since for shifting problems. When pulling uphill it would shift to limp mode but recover on the down hill. Same with pulling away from a stop, long delayed shifts.

Got it back from the Trans Mech today. He told me there was a broken bolt on the battery and while testing he noticed the battery light would come on in conjunction with the shift problem. He replaced a bad battery bolt and fixed the problem. Apparently the electronics in the tranny want to have all the voltage they can get in order to work properly.

BTW all this work has been done under the mechanic's warranty.

Interesting. Are you refering to a bolt that secures the cable to a battery post?

I don't want to rain on your parade but I find this hard to believe because even if there was resistance to the battery the vehicle itself would still be producing a higher voltage than the battery assuming of course that the charging system is operational.

Of course I have been wrong many times before.

Yup, the bolt that clamps the cable to the post. I also replaced the battery today, the other battery was 2 years old (4/2005 purchase) and sat in the van for about 18 months while waiting cash to fix the tranny. During that period the van was started and run about once a week to keep the engine loose, but had to be jumped quite frequently during the last few months. So it was probably a combination of a loose connection and a badly sulfated battery that was bringing the whole electrical/charging system down. I'm taking the old battery back to Wally World as it is still a month within the 2 year free replacement warranty.

baumbr,
Interestingly, I just had the tranny on my 99 windstar rebuilt at Aamco. I too have had problems with the battery light coming on intermitently before and after the rebuild. Aamco said my alternator was bad and probably caused the tranny to go. I took the van to Advance Auto Parts and had the battery and alternator tested. The battery was bad -10.5 volts- but the alt. was OK. However, the bat light still comes on, accompanied by a shudder-can't tell if it's trans or engine-leading me to believe that the alt might be bad after all. Or the shudder could be a consequence of the P171 & P174 codes coming up since the rebuild or maybe it's time for a tune-up @ 97,000 miles. So, I'm not sure if it's all related or coincidental, but I still have an electrical issue that warrants further attention.

Now that its being mentioned here... my 2000 3.8L used to shudder while coasting and adding just a tad bit of throttle. After replacing the battery while tracing a miss in the engine (which turned out to be a bad damper pulley by the way) the shudder has not come back ever since!
So there may be a direct link.
I had the P0171 & P0174 codes fixed over a year before the shudder started, so I don't think its related. But I think it must have to do with the eletrical system since this trannys are electronically controlled.

The transmission is electronic controlled....which REQUIRES that the supply voltage be within a given range in order to operate correctly.
I would check all battery connections and grounds......
Also.....at 97K miles.....I would make sure that all the tune-up items are taken care of....including the TSB for the P0171/174 (1999 and newer ONLY), spark plugs, spark plug wires, maybe even coil pack, fuel filter, fuel system cleaner.........etc

Check the main battery ground cable, it is connected to a tranny mounting bolt.