hi new to site, i have 2 broncos, 1986 and 1987 both are auto, both have transmission problems. the 86 hesitates for about a minute or 2 when you put it in gear but other than that pulls fine. the 87 has no reverse, and slips bad in high gear, also have to let off gas to shift. i been online looking at identification guides, and general descriptions. i would love to get a whole parts truck and convert the 86 to a standard, rebuild the 86 and put it in the 87. it sounds like i got AOD's, i am going to crawl under and id tomorrow. if decide to get a used trans, i wonder what would be the ideal heavy duty, and what car or truck to look for it in. also i am sure i will have to do a certain amount to it before installing it. thankz for any help.

 

Depends on what engine you have. If the transmission has overdrive, it's an AOD It's pretty much a given if you have a 5.0 EFI. If that's the case you're stuck with it, but they can be built up. The 351Ws came with a c-6.

 

yup, i crawled under it, its a c6. 86 has a 351w, tranny has 17 bolts L shape lower portion is rectangle shape. the 351 is carburetor (holly), plenty of power, but she just drinks gas. i would like to buy whatever it needs, and hope i can put it in without having to pull it out of the truck.

the 87 has a fuel injected 302, tranny is a AOD i think, it has 14 bolts angled corners in the rear, and a hump in the middle. would i be on the right track to put a c6, 4r100, e40d, in it.

 

86 has P RND21 , 87 has P R N (D) D 1

 

You cannot replace an AOD or a C-6 with a computer-controlled transmission such as a E4OD or 4R100 without getting a computer of some sort to interface with the tranny. The existing PCM can't do it.

For either vehicle, the easiest heavy duty option is a C-6, and you would have to deal with crappy gas mileage due to no overdrive.

 

OK Thanks, guess i will keep to the model that it comes with. rebuild and or beef up the AOD.