Drivetrain Transmission problems...

Discussion in 'Fox 5.0 Mustang Tech' started by Cory Berg, Mar 29, 2013.

  1. So yesterday I changed the transmission fluid because the previous owner was running straight gear oil. I filled it up with Dexron III like the manual says and now it grinds 3rd and 4th when down shifting. Any ideas?
  2. I believe some early years t5 actually called for gear oil because of the synchros they used
  3. Depends on what year t5 you are running as mentioned above and also how did you fill it ? is it possibly undefined ?

    Sent from my iPhone using my fingers
  4. All t5 trans call for atf..your syncros are shot..I've seen gear oil destroy many t5 trans...expect the worst hope for the best on your rebuild

    Sent from my SPH-L710 using Tapatalk 2
  5. Been there done that. My tranny had gear lube in it from the PO and when I switched to ATF it was all bad after that...
  6. The tranny on my '86 gave out before I realized the PO had used gear oil in it. The smell was unmistakable when I swapped in a new one.
  7. If you are not in a postition to replace the tranny and need to try something, you could drain the tranny really well and refill with Honda ATF. It is just a band-aid, but does work on worn synchros. I had a T56 that was using stock Dexron, and started grinding into gear, I heard about the Honda ATF trick, and did it. It stopped all the grinding so long as I wasn't powershifting. It ran like that for 30k miles when I owned it, and then the next owner never had issue with it for as long as I kept in touch. For all I know, it still might be on the original tranny right now.
  8. Thanks Ratio, I'm not really in a position to replace it. But, I have good news because the grinding has stopped. It only happened during the second and third drive. Now it's a little stiff but no grind. Should I start planning a rebuild? And if so, is the general rebuild kit all I need? The car is just a daily with maybe some occasional autocross and track days.
  9. Grinding doesn't just go's a sign that syncros and internal parts are in their way out..u may b ok now but plan for the future.

    Sent from my SPH-L710 using Tapatalk 2
  10. All NWC (non world class pre-85) T-5 use 70WT Gear Oil or Redline MTL.
    ALL WC (world class after 1985) T-5 use ATF.
    My transmission builder "Hanlon Motorsports" recommends NON synthetic after a rebuild. Why? Because the new fiber blocker rings need to grab a little to spin the next gear up to speed so it will mesh in quickly. A synthetic has too many slip additives and may cause a rake when shifting. On the other hand as ratio411 said, a slippery fluid like the Honda stuff may cause the gears to slide together without a grind if you have a T5 which has the OEM blocker rings.
    As for the noise going away, after the Dextron got slung around good it may very well have gotten better. Keep us posted Cory.
  11. Sure I've spoken with Bob Jacob.hanlon on many occasions ...learned off his t5 how to video and have been building t5s for over 5 years now..

    I agree with the synthetic assessment...I always run regular atf too

    I've always run atf even on the older units..there is actually some debate on atf vs gear oil on the nwc units..due to the brass bushings and syncros the nwc units seem to b able to take either fluid

    Sent from my SPH-L710 using Tapatalk 2
  12. When I changed it, the oil had a pretty intense bronzy glitter to it. Is that to be expected anyways because of the brass synchros?
    Thanks gearhead, I will keep posted if anything else happens. Right now everything seems ok. *fingers crossed* As for a rebuild, I'll put it in the plans but it may not be for two to three months.