i have a 1990 f150 4x4 5.8 e4od trans with 35 in tires. has 3.55 gears. what speeds should it shift at when stock tires are on it and driving normal? i get 15,25,35 and then 45 but speedo hasnt been calibrated with new gear yet. does speed,mlps or tps determine shift speeds? or what does? reason im asking is it shifts fine was rebuilt a year ago . it will down shift and upshift when im at 35 but if i stay above it its fine same at 45. down then up unless i run over 45. no od light flashing at all and no codes.if i switch the teeth gear at transfer case would i need a 16 tooth gear? i think i have a 19 now.any help or ideas guys would be great. thanks

 

Shift points all depend on a number of variables; load, TP, etc. When it shifts isn't constant, it might shift from 1st to 2nd at one speed, and the next time it 1-2 shifts might be at a higher or lower speed depending on how you're driving it. Not really understanding what exactly you're saying the problem is, can you clarify? Also, did the shifting problems start when you wen to the larger tires?

 

what im saying is under normal driving not hard acceleration just normal easy driving those are the shift speeds all the time. no the big tires didnt start this i had the tires on for a cpl yrs. then trans went bad had it rebuilt and then it does this. if i keep it above 45 like say 50 it will stay in overdrive. if i cruise at 45 or so it will drop down and then back up down and up down and up etc. around town at slow speeds no problems unless i cruise at 35 or so and then it does the same thing. but if i go 40 and switch od off its fine, i heard that when u have a e40d rebuilt with upgrades u should upgrade your pcm to at 1994 year. any one know about this? says if u dont it could cause shift issues also. any help on wich pcm i need to get? it didnt do this with old transmission so maybe i do need to upgrade pcm. any ideas guys?

 

I have never heard that myth before. There is no reason to change your PCM simply because the transmission was rebuilt. In the event the rebuilder changed your solenoid pack, that is a different story. 1995 and later moved the protection diodes from the solenoid pack to the PCM. If you use a 1995 and later solenoid pack with an earlier model PCM then you can run into problems such as blown solenoid drivers. I seriously doubt that is your issue.

I say start with the basics, check for codes then proceed accordingly.

 

was just wondering if the issue im haveing could be the torque convertor lock up and unlocking? it seems like it downshifts revs a little and then kinda slams into gear. not real bad but that what it seems like. if i take the od switch and turn off it doesnt really do it . i have no codes other than 33( egr) my old trans didnt do it but the codes i got on it then said torque converter clutch excessive slipping etc. even blew fluid a cpl times from getting hot. maybe converter wasnt locking up now it is and i can really notice it at lower speeds with the big tires. also where do i get the 15 tooth speedo gear and how hard to replace? its on the back of transfer case.

 

it was the vss on the transfer case ( vehichle speed sensor) i did the lock up switch and that didnt make a difference still did it. so igot to thinking about the vss. i replaced it with an autozone one( 19 bucks) and got a 16 tooth speedo gear from ford( 3.50) and now she works great and speedo is on. funny though everything i read said i had either an 119 tooth gear or 21 and mine was a 18 tooth. anyway guys replace vss when u start having problems with no codes. saves alot of headaches and maybe cash.

 

Great feedback, thanks!