1991 F150 with 81k mile (really) lurches when going into OD, all other shifting is great. Is this a band adjustment? Tranny never been serviced. Getting ready to change fluid & filter.

 

If you have 81,000 miles on the original transmission and original ATF, changing the fluid is going to get iffy. The issue is the old ATF has gone to varnish, no doubt. Changing it will remove the varnish. You may end up having to reseal the transmission. There's no real way to tell you if it will or not but be prepared anyway. The 91 AOD was a major POS. Ford replaced the one in my Bronco 6 times under warranty. I have friends that bought them back when they were new and all had to have replacements. There was an issue with the pickup tube, as I recall it being named, that caused the pressures to be low and subsequent heat just self destructed the unit. My second transmission was replaced in Albuquerque New Mexico. The hiway, IH40, from Santa Rosa to Klines Corner is a pretty steep and long road. By the time I got to the top of it, the bottom and rear of the Bronco was ATF as it boiled out of the dipstick tube.....and I had a 4000lb rated transmission cooler on it in addition to the Super Cool factory cooling system. Another item to watch, the OD switch on the dash is prone to moisture. It can leave you on the road with no functioning transmission. The immediate fix is pull the panel, then disconnect the OD switch.

 

I thought only the E4OD had an overdrive switch, the AOD was controlled by the shift lever? Park, Reverse, Neutral, Overdrive, Drive, Low?

E4OD/AODE/4R70W is electronically controlled, AOD is not. AOD uses a TV cable.

 

I have the AOD. I called a local FORD delership, They wanted $125 to look at the truck a talk about it. So, I went by a local tranny shop and he said don't worry about it. No need to spend the $ on pulling down the tranny for something that maybe only a OD seal with everything else working good. Im going with Amsoil fluid which can soften seals and may even help the problem. Thinking about changing the fluid & filter myself.

 

If you do change it yourself, also pull the torque converter drain plug. You will need about 12 quarts. Pan drop only gets about 4 quarts out.

 

Yep, my comments are on the E4OD, not the AOD. Sorry.

 

Does the 91 have a torque converter drain plug!

 

It should. I think Ford had them till about 2001.

 

Ok, I'm not a auto tranny guy so I assume if there is a drain plug on the TC you get to it after you drop the tranny pan? Tap crank the engine to spin the TC to get the drain plug down?

 

You access it through the dust plug under the bell housing. You can tap crank, or put a socket and breaker bar on the crank pulley bolt.

 

Strange...I don't have a "dust plug" under the bell housing. That would have been obvious. This is why I am having such a problem. This trans must be a warranty replacement or something. The sump pan says Automatic Over Drive Metric on it.