Hi,

I've got a 2000 F-250 SuperDuty with the 5.4L V8, and a standard transmission and about 140k miles - just bought the truck several months ago. Trying to figure out what's wrong with either the transmission or the clutch. Here's the symptoms, any feedback is welcome:

1. If I shift too quickly into 5th from 4th, say 'pushing' from 4th to 5th directly, it grinds and chunks in every time.

2. If I shift slowly, 1-2-3, 4th into neutral, neutral and push right to line up with 5th, then into 5th, slight pause on each move, then it usually shifts into 5th silently and no problems ...but sometimes will grind just a tad.

3. If I shift from 4th into Neutral, leave it in neutral and let the clutch out then step on the clutch all the way and wait before shifting into 5th ...even if I wait several seconds (say 'close to 10 seconds'), it will grind every time ...a good grind that bugs me to do. I'm careful to avoid this.

4. Usually, if it grinds into 5th, I can shift down to 4th, let the clutch out and drive a short way and try again ...and it'll grind again. Best way to avoid grinding into 5th is to drive normally, and use the 1-2-3 'slight pause' method of shifting into 5th. This is what I do all the time, trying to make the tranny last as long as possible.

It's like the 5th gear synchro isn't working well, or perhaps the clutch is not fully disengaging? Advice welcome... what's wrong? I wonder if the truck (haven't looked it up yet) has a hydraulic clutch and maybe the clutch is not fully disengaging ...pumping the clutch pedal sometimes seems to help, but most often doesn't. Sometimes, I have difficulty shifting back down into lower gears as well ... no grinding, but you have to double clutch just right to get it to go into gear (3rd, or 2nd).

Hmmmm....

Thanks in advance,
Brian

 

First, check the fluid level and the quality of the oil. If it's good, you likely have a syncro that is failing.

 

It sounds like its the Syncro's, if it was the clutch it would do it with all the gears.

 

Thanks for the info on the clutch not releasing symptoms - helps a lot! I will check fluid level and condition, and may change it as well....

I grew up on an onion farm in Oregon. The old harvesters wouldn't fit over the top of the newer trucks (as in 'newer than about 1953') since the newer trucks were taller, so we kept a lot of old trucks going and avoided having to replace harvesters - your basic mom and pop onion farm with no spare money. A few of those old trucks either had no synchros at all, or they were so worn out that they acted as though non-existent. I learned how to drive, when to shift, many different tricks of the trade that helped shift up and down, judging timing and rpms, tricks for shifting the differentials, even driving with no working clutch at all (including full stops and shifting as necessary to get the truck back to the barn) ...I think I can live with my current tranny as-is for awhile. The motor uses a quart of oil between changes too... I will rebuild and fix as it becomes required I suppose.

Brian

 

If you don't already, time to learn how to double-clutch.

 

FYI: I've been double clutching for about 45 years now, probably since long before most of the folks here were even born. That said, note that my issue is with UP shifting from 4th to 5th. Double clutching is a DOWN shifting technique and won't help me. It's purpose is to spin up the transmission for the next gear down since it will be spinning faster after you've completed your shift. We had to do this with our un-synchronized farm trucks, else you WEREN'T going to shift down (and everyone in the county would hear who's driving...).

You can double clutch now, even with today's nicely designed synchros to help your synchros last longer, and you may need to anyway. For example, when either a) the synchros are wearing out and you HAVE to do it, or b) do it anyway just to match gear speeds to reduce the work and wear on the synchros. If you ever experience a bit too much resistance when shifting down, synchros or not, it's wise to double-clutch to help get the gear speeds matched - so the synchro can do it's job easier.

The best way to double clutch is to:

- Shift to neutral and then let the clutch out

- Rev the motor (clutch still out) to above the rpms that the next gear will need (the tranny will be coasting down again while you complete your shift and synchro's seem to work best 'from the top', gears on the slow-down)

- Step on the clutch again and shift into the next lower gear. You can skip a gear, but you will have to rev the motor a lot higher if you do - probably a lot higher than you'd guess (try it)

It's pretty quick once practiced, and like I said, it's a good way to help those synchros last longer rather than forcing the gears as you shift down. If you are driving a rig that has no synchros, you will also need to learn to judge speeds/rpms/gear requirements so the gears will mesh without grinding when you put the tranny back into gear - and this tends to be easier if you shift into gear (on a down shift) while the tranny's coasting down as well.

Brian

 

Double clutching is a lost art. I was taught to double clutch on up and down shifts for non-syncro transmissions. I always found it equally effective. The whole idea, as you stated, is to match up the gear speeds to allow engagement.

 

Syncros on its way out or shift linkage is out of adjustment or both. If the external adjustment doesnt get it MAW (might as well) tear her apart inspect and rebuild. Was the fluid ever changed? Drain it and inspect for debris. If the fluids never been changed its likely ready for a rebuild. But try adjusting that linkage. Then out it comes for an inspection. Look at the clutch and flywheel too while your in there. Get it before you chew up gears then it gets expensive. If it has the original clutch its likely ready for one at 140K

 

Linkage? That might just be it... In my case, the 5th gear synchro appears to work beautifully, but once in awhile, and occasional shift into 5th will act like there's no synchro at all and it'll grind-kachunk into gear (hate that!). Try it again by shifting back into 4th, accelerating a tad, then re-shifting into 5th and it'll work perfectly again. It 'feels like' the synchro is working when it does, e.g. you feel pressure on the stick that prevents going into gear for a sec, then it slides in. All other gears synch just fine, up-shifting or down (although I nearly always double-clutch on the way down, and always when hitting a climb).

I have no clue on the linkage ...I've had this truck for only a few months. But I will look into it... it'd be wonderful if only an adjustment was needed, second best if linkage needed replacing, and worst if I have to rebuild the thing (in which case I won't ...I'll wait for the carnage and put a rebuilt one in).

Brian

PS: While the truck has been very pampered (looks like new inside and out, good mechanical condition and no leaks etc), the guy that owned it before me was on the cheap side ...hadn't fixed the leaky power steering pump, had cheep granny tires on it - 'highway miler' tread pattern on 235/85/R16s ...yechh! I'll bet the fluid hasn't been changed ...but I'll gladly do it.

 

Double clutching up is also useful. Especially on a truck transmission that has heavy shafts in it. The engine will slow the shafts down instead of the synchros.

 

Again ...interesting! Something new! I guess the trucks that I drove when growing up (no or worn synchros) weren't big enough. They were all 2-1/2 ton and 5-ton trucks, but were old trucks (late 40s, early 50s)

bd

 

I think the synchronizers were better made. ZF-5 and ZF-6 are known for crappy synchronizers.

 

You double clutch up or down with an unsynchronized transmission. Some unsynchronized transmissions, simply by nature, slow the input shaft down enough to make the shift on it's own with a "single clutch".

you only rev the engine between shifts when going down. you let off the throttle when up shifting.

You can also shift without the clutch if you know the vehicle and gearbox well.

My ZF-6 shifts fine, but will grind if I try to shift 1-2(2nd to 3rd) and OD-4 (6th to 5th) too fast.