Transmission friction modifier question

Bosch

Registered User
I've been searching for a couple hours now and keep finding conflicting information. First thing - i'm getting a crunch when shifting at higher speeds from 1 to 2 in my 1990 5 speed - occasionally, sitting at a red light, rowing through the gears, it'll crunch then as well. I don't know all that much about transmission internals(i couldn't identify jack ~~~~ if you showed me a cutaway, i just have a very basic conceptual understanding of how they work). My guess/assumption would be that a synchro is starting to wear out. I don't think it's a clutch or slave cylinder issue, since no other gears present a problem. Anyway, on to my question.

Before paying out the ~~~ for a transmission teardown and rebuild, I'd like to just jack up the car and check for low transmission fluid and give her a top up to see if that would help. I know the factory manual says add the ford friction modifier, but is that to make it have LESS friction or to have MORE friction? I can't figure it out based on my searching of these forums. From my understanding of what's going on inside the transmission, I would think that I'd want MORE friction so the gears and synchro and whatever all clunk together more reliably than they are. Can one of you old timers(sorry but it's true) shed some light on my question for me?
 
>I would think that I'd want MORE friction

Correct.

AFAIK, modifier for the trans is meant to -increase- friction on the synchronizer rings. Those are responsible for helping the gears match rotational speed as they make contact and reduce clashing when shifting. The sooner/better they grab when mating, the sooner the gears involved can sing the same song.
 
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I've been searching for a couple hours now and keep finding conflicting information. First thing - i'm getting a crunch when shifting at higher speeds from 1 to 2 in my 1990 5 speed - occasionally, sitting at a red light, rowing through the gears, it'll crunch then as well. I don't know all that much about transmission internals(i couldn't identify jack ~~~~ if you showed me a cutaway, i just have a very basic conceptual understanding of how they work). My guess/assumption would be that a synchro is starting to wear out. I don't think it's a clutch or slave cylinder issue, since no other gears present a problem. Anyway, on to my question.

Before paying out the ~~~ for a transmission teardown and rebuild, I'd like to just jack up the car and check for low transmission fluid and give her a top up to see if that would help. I know the factory manual says add the ford friction modifier, but is that to make it have LESS friction or to have MORE friction? I can't figure it out based on my searching of these forums. From my understanding of what's going on inside the transmission, I would think that I'd want MORE friction so the gears and synchro and whatever all clunk together more reliably than they are. Can one of you old timers(sorry but it's true) shed some light on my question for me?

You only want what is required. If you had no issues before and its gradually started to grind you probably will need a tear down to replace the blockers. You can inspect the blockers taking the top cover off, unfortunately the trans needs to come down to do that. Recently I had dropped the trans several times last year each time losing fluid out of the output shaft area, I kept filling it up with just trans fluid and third gear grind was pretty frequent on speed shifts and quick shifts. I decided to do fluid change with modifier and new oil again, I used two qt. Pennzoil Synchromesh, one Ford Modifier bottle and rest of the top off with regular Mercon III. After a short time allowing the fiber blockers to soak up the modifier I got my normal shifts back.

The way I understand it the modifier alloys more slip not less so the friction material doesn't get damaged. Same applies to the differential, without the modifier you will slow things down too much and wont allow the last bit of slip to synchronize the sliders with the gear. If I am wrong on this please elaborate.

Also a bad clutch will cause shifting issues, if the disc has exploded and have wedged lining material, it will act like the clutch is engaged, this is an extreme situation but has happened to me after burn outs. Basically anything clutch related that prevents the input shaft from slowing down to 0 revs you will have shifting issues. And if the blockers are toast same applies, things cant slow down fast enough to synchronize the different speeds the components are moving at.
 
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