Fmx slipping from 2nd to 3rd gear

Joined: May 24th, 2018, 5:08 pm

May 25th, 2018, 9:39 am #1

Hi guys, I am having a problem with the shifting of my freshly overhauled FMX Transmission out of my 69 Mustang.

Everything inside the transmission is new except from the two brake bands which seemed to be still fine. I have done a few FMX Transmissions and all work fine.

Problem is:
I start in D.
Under very light acceleration (nobody would start that slow from a traffic light) the shifts from 1 to 2 to 3 are fine.

I start in D.
Under heavy acceleration, nearly before the rear wheels are spinning starting from a stop the shifts from 1 to 2 to 3 are fine as well.

But when I start in D and accelerate normally it will shift very smooth from 1 to 2 (fine for me) but slips for a short moment (rpms increase lightly) exactly in that moment when he shifts from 2 to 3.

If I shift manually from 1 to 2 to 3 everything is fine as well so I would assume an error in the valve body?

Any ideas are appreciated

Best regards
Quote
Like
Share

Joined: May 24th, 2018, 5:08 pm

May 25th, 2018, 12:30 pm #2

What I forgot to tell :

During the rebuilding I also put a new modulator in. After the issue occurred I swapped back to the old one but the issue persists.
Quote
Like
Share

Joined: November 18th, 2004, 4:20 am

May 26th, 2018, 4:45 am #3

How did you adjust the front band?
Quote
Like
Share

Joined: March 23rd, 2004, 11:14 am

May 26th, 2018, 6:10 am #4

As Stuart said , front band adjustment. There is a few different interpretations of the correct method.

Also how was the Modulator adjusted . A slight adjustment in may tidy it up. 

Also assuming the top gear clutch clearance was well within spec ? 
Quote
Like
Share

Joined: May 24th, 2018, 5:08 pm

May 26th, 2018, 6:22 am #5

Hi guys,

I used the badshoe video for overhauling and did the adjustments exactly as advised with a torque wrench and the 1/4 spacer between adjuster screw an servo. All clearances were within the specs.
Turning the screw in the modulator half a turn didn't change anything.
Quote
Like
Share

Joined: November 18th, 2004, 4:20 am

May 26th, 2018, 1:35 pm #6

After torquing the adjuster and removing the spacer what did you do next?
Quote
Like
Share

Joined: May 24th, 2018, 5:08 pm

May 26th, 2018, 1:51 pm #7

Hi Stuart, we are talking about the intermediate band, don't we?

1/4 spacer then torqued it to 10 inch pds
Removed the spacer and ran the adjuster in an additional 3/4 turn, then fastened the lock nut.

Regards
Quote
Like
Share

Joined: November 18th, 2004, 4:20 am

May 27th, 2018, 7:37 pm #8

If you are sure about the direct clutch clearance and band adjustment next step is valve body. Provided the band isn't glazed. 
One rare occassion I saw the drum support cracked. That is the one pressed into the drum. 
Drove me bonkers.
Quote
Like
Share

Joined: May 24th, 2018, 5:08 pm

May 27th, 2018, 7:41 pm #9

I have to drive the car roughly 700mls before I can tackle the valve body. Drove it today with manual shifting and that worked very nice. Am I right that this will not harm anything?

From my understanding the manual shifting simply overrides the valve body intelligence, is that true?
Thanks for your hints guys!
Quote
Like
Share