Longgone
John/68 Barracuda & Dart
I have an 833 in my 68 Barracuda and it shifts nicely when the engine is cold, but the more I drive the harder it is to shift,especially going into 3rd. Any ideas?
4spd shifting difficulties
- Thread starter Longgone
- Start date
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demon seed
The Original Demon Seed
If you're sure that the shift rods from the shifter to the transmission are adjusted correctly then the other problem might be that the clutch is not adjusted correctly. When the clutch disc (friction plate) gets hot it will grow in thickness, .010"-.015", and therefore if the clutch pressure plate does not fully disengage, when you push the pedal to the floor, it will make it hard to shift. How far do you push the clutch pedal down before you can feel the clutch starting to activate (called freeplay). The other problem that could exist is that there should be a bronze bushing pressed into the end of the crankshaft that the noze of the transmission input shaft fits into. If the clearance between the I.D. of the bushing and the O.D. of the input shaft is to tight the input shaft will remain connected to the crankshaft (friction) even when the clutch is fully disengaged.
There is a third possibility but I don't think temperature would necessarily have a part to play in this one. One of the engine crank bearings doubles as a thrust bearing for the crank. When you depress the clutch pedal the clutch throw out bearing not only pushes on the pressure plate to disengage the clutch, it also is pushing on the crankshaft and pushes the crank up against the crank thrust bearing. A worn thrust bearing will cause you to loose some of the travel needed to disengage the clutch.
There is a third possibility but I don't think temperature would necessarily have a part to play in this one. One of the engine crank bearings doubles as a thrust bearing for the crank. When you depress the clutch pedal the clutch throw out bearing not only pushes on the pressure plate to disengage the clutch, it also is pushing on the crankshaft and pushes the crank up against the crank thrust bearing. A worn thrust bearing will cause you to loose some of the travel needed to disengage the clutch.
Longgone
John/68 Barracuda & Dart
Thanks Demonseed, the clutch is adjusted for 5/32 play at the rod which is supposed to equal 1" freeplay at the pedal. I think it`s actually a little more at the pedal so I`m going to start there. Oddly though it seems that only 3rd gear is being stubborn, 2nd and 4th are never a problem, I can even downshift to first before stopping.Hopefully I`ll get a chance to work with it this weekend if the rain stays away.
A
Ace
Guest
How many miles on it, and what oil is in it? Your description of the cold vs. warm behavior, and that it only seems to affect 3rd gear would lead me to believe the 3rd gear synchro is going out. It has enough friction to grab when the oil is cold, but loses it when the fluid thins out after it warms up.
Balky shifting caused by most anything else (including everything mentioned by demonseed) manifests the other way 'round WRT temperature (cold makes it worse, except for heat expansion in the clutch, which is extremely unlikely), and affects all gears.
It might last awhile longer w/heavier oil, but cold shifting will suffer. Coming up on summer soon, so what the hey? :salut:
Balky shifting caused by most anything else (including everything mentioned by demonseed) manifests the other way 'round WRT temperature (cold makes it worse, except for heat expansion in the clutch, which is extremely unlikely), and affects all gears.
It might last awhile longer w/heavier oil, but cold shifting will suffer. Coming up on summer soon, so what the hey? :salut:
Longgone
John/68 Barracuda & Dart
The trans has 68k on it, but the car was seriously drag raced. 12.5 to 1 ,big cam,blowproof, d/s loop,4.56 gear, that sort of set up, so I know they were`nt easy miles. I`m thinking synchros too, but I was hoping someone would tell me something else. I`m running 140w in it now per the manual and recently drained a quart and added a Lucas treatment.It didn`t seem to make any difference. I hope I don`t have to rebuild it ,but I`ve had to rebuild everything else ,so it would`nt come as a surprise.
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