i own an 88 bronco which i bought from some crook in fort worth. its been used for towing and the transmission was ****ty before i got it rebuilt. the speedometer still doesn't work properly probably because of the little gears the speed sensor plugs into, since thats the only thing i didnt replace, so i dont know if the speed sensors doing its job or not. when i first start up to go it will feel like the engine ain't pushing its weight. itll rev at the proper rpms for how im accelerating, it just won't pick up. if i floor it the engine will rev up quickly and drop back down before starting to pick up and leveling off at around 3500 rpms, after keeping my foot on the pedal for a while at these rpms, itll pick up quickly and shift beautifully. i work at oreillys and have done a diagnostics and repaired all the problems the computer has told me, except the throttle position circuit reaching its maximum voltage. i also have internal oil leaks i guess the valve seals since it shoots out my exhaust when i rev it up. its a 302. im gonna drop a 351 in it but want to fix this problem for the time being. the only thing i could think of is the computer learns the proper shifting points and speed after i floor it for a while, and forgets it when i turn it off.

 

Do you have the AOD or the E4OD tranny? The E4OD is computer-controlled, the AOD is not. IN either case, the speedo gear is inside the transfer case, so check the cable and the gear for any wear. THE problem sounds like it may be related to the TPS (throttle position sensor). 3500 RPM's seems VERY high to me, as I would be doing 80 mph with my C6 without OD. You may have an engine problem like you stated, or slippage in the tranny or rear axle. I would at least pull the cover off of the rear axle and look at the gears.

 

need to know what year and tranny. if its an e4od then your VSS located in the rear diff talks to your tranny about speed an proper shifting along with an MLPsolenoid on that tranny as well. check both and replace if necessary. if your gonna do the 5.8 swap I dont see a point in putting money into what you have now. if it runs ok just deal with it till its time for the swap but start looking for a motor now.

late

 

it has an AOD tranny but whats going on is itll pick up quickly and climb rpms and shift beautifully after ive been romping on it. it doesnt have a thermostat.

 

how long are you letting the rig sit running before you leave because i know my aod likes at least 5 mins first thing am to warm up good before driving

 

O.K., so the 88 Bronco, Ford8.8" rear axle and the AOD tranny. I would say check the tranny pan for sawdust (old crook's trick), but you said you had it rebuilt after buying the Bronco? It may not be shifting right due to mis-adjustment of the linkage, check on that. The AOD is not computer-controlled like the E40D. Your 88 still has a speedometer gear, so should not have the VSS or speed sensor in the rear axle (speed density system after 1992 to 95). Maybe KB can correct me or add to that some more?

 

correct no speed sensor in the rear axle. speed density stoped in late 93/94 in cali only then 95/96 was mass air everywhere but mainly with 302's a few 5.8's had mass air but were still fewer.

i think it just might be time for a tranny service. it should be done every 6mnths to a year. and should have been done about 1000-3000 miles after getting that tranny rebuilt.