69 Mach 1 FMX shifting problems!!! HELP!!!

[PCGamer]

Purchased car recently with a fresh motor\tranny rebuild. Have receipts and have previously spoke with shops that have done the work...

Motor (351W) has been rebuilt as if it were a new long block.. Has edelbrock 650 carb, with a performer intake. Tranny (other than torque convertor) has been completely rebuilt i.e. front servo, clutches, bands, seals, etc. etc. etc.....

Both motor and tranny have about 900 miles on them...

Within the first 20 mins. or so with a cool engine/trannsmission the transmission downshifts and upshifts correctly in all gears regardless of accelerator pressure even if it is floored....

Once things are heated up (after driving for about 20 min. or so) this is when things start... The tranny shift point between 2nd to 3rd (ONLY) is not occuring at WIDE open throttle (FLOORED) until I let off on the throttle and engine rpms DROP to around 3400 then it will finally shift into 3rd gear. Again this is ONLY happening once the tranny is heated up with the accelerator FLOOED... Otherwise even when heated up the tranny will shift fine except once again only when the accelerator is FLOORED...

I've replaced the vacuum modulator and checked the fluid. Unless the modulator is bad I'm not sure what this. The tranny is basically brand new with low low miles... The car was purchased out of state so taking it back to where the work was done is NOT an option.. Im hoping its nothing expensive...

Im thinking maybe its a vacuum issue but again while only once the engine is hot and the pedal is floored???

Please Help..

PC....

[Phillyfanfrombirth]

Do you have a kickdown linkage on it?

That sounds like the linkage is out of adjustment...

[PCGamer]

ya.. as a matter of fact I the linkage now has the correct adaptor from edlebrock for my engine/tranny combination.. Wonder if i did anything to the setup in changing it over...//..

The thing is is that this problem does not exist when the engine\tranny is cool.. So im thinking how could this be a kickdown issue then ya know..//...

I dont know, Im not a gearhead just a novice needing help..

thanks for responding...

PC...

[Phillyfanfrombirth]

Just like most any fluid... higher temperatures change the dynamics of transmission fluid.

If you are going to "floor" it in 2nd gear, don't expect it to shift until you are way up there on the RPM band... like say 5500 or more... its like that for a very good reason. If you are getting off of a highway ramp, and are flooring the thing to merge or get up to speed, you want that thiing maxed out in 2nd gear before kicking into 3rd...

Maybe the question should be... what the heck do you think you are doing by flooring it in 2nd gear and going so fast?

LOL!

[PCGamer]

because with an aftermark 3.70 gearing Im only at around 65mph... In addition regardless of "fluid" dynamics, should I notice that much of an rpm change from 4K with fluid cold to 4500 with fluid hot and it not shifting into 3rd yet??

What IM seeing is the engine whining out. It still has more pull at 4500 rpms, but it seems to me I am really pushing the envelope here..

regards..

pc..

[Phillyfanfrombirth]

With 3.70 gears? Yes. 4500rpms should be well within your rpm band. I'd be getting uncomfortable over the 5500rpm level.

If you are not comfortable with your current level, you should be able to adjust that linkage to suit your needs... And adjust it to suit your "warmed" needs.

[PCGamer]

Thanks for the replies..

Anymore,, keep them coming a..!!..??..


Thanks ..

Mike

[70DropTop]

Check the vaccum lines coming from the throttle body to the tree on your firewall, if it looks worn/hard replace it. Also check the vaccum caps on the tree, sometimes they will crack and you cant see it as may be on the back, recommend replacing them for a couple of bucks from an auto parts store. The vaccum line going from the tree to the hard tube connector on the modulator could also be the problem, best bet is to replace all rubber parts as they are cheap and doesn't take a lot of time... Where does the carb/throttle vaccum between the firewall and the manifold connect at? Mine was on the carb (Holly) body and I moved it down to the throttle body for more draw... Worked for my 70 Stang vert with 351C/FMX/3.00, but mine had crappy shifting and always wanted to start in 3rd gear when you put it in D. Still havn't replaced the modulator though...