zf 5 question

I've searched so many threads my head is still spinning. Plus the fact that the search function likes 4 letter words... I have a few choice 4 letter words for it.
The 6.9l started leaking at the block heater. Popped a new freeze plug in, saw a crack by the bore. Ripped it out for the 7.3 i have in the parts truck. Swapped in the ZF5. Before i dismantled the truck, i drove it. Drove quite well, just smoked as the pump was off a turbo truck and was turned up. I drained the tranny, no metal, clean. Shifted fairly well. Just tossed both in my truck, did the auto to manual swap. new SMF clutch, new slave, new master. Have perfect travel for release. tranny will grind from 1-2 when its cold. Go a mile or two and its pretty good. I refilled the tranny with a synthetic blend merc V. I drained that out for Redline MTF. Total glitter. Kinda pissed. Its much better with the Redline but its not where it should be. Gotta shift slow on the 1-2 shift when its cold. Going from 3-2 or 2-1 is fine no grinding. Before i tear this box apart to throw some syncros at it what do you all think? Should i try royal purple atf? Syncromax?

A little trouble between 1st and 2nd is normal. The gear spread is pretty wide between 1st and 2nd, so it's hard for the tranny synchros to keep up. A hint I got from another zf owner was to start out in 1st and just get the truck moving, and don't rev the engine really high in 1st before you shift into 2nd. This method works really well.

As far as the oil is concerned, why not try what the tranny manufacturer called for? Dexron auto tranny fluid.

Well Mercon V is suppose to be backwards compatible?

It shifted like total crap with mercon V in it.

No idea on the grind, but I will say that I don't understand the reasoning that "a little trouble between 1st and 2nd is normal). Franklin2 - this comment is not meant against you or your experience so please don't take it that way. I am simply saying that my 94 with a zf5 has ZERO grinding or shifting issues going in or out of any gear at any speed. I have no idea what it has in it for fluid, I have driven it for the 25K miles I have owned it and never changed the fluid. I don't think you should have any grinding issues if everything is correct... that doesn't mean that the problem isn't normal.

coletrain777 said:

No idea on the grind, but I will say that I don't understand the reasoning that "a little trouble between 1st and 2nd is normal). Franklin2 - this comment is not meant against you or your experience so please don't take it that way. I am simply saying that my 94 with a zf5 has ZERO grinding or shifting issues going in or out of any gear at any speed.

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This is what I am talking about; Go out and start your truck out in 1st gear and wind it up to around 2500 rpm, and then quickly drop it into 2nd. You should find there will be some slight delay that is not there in any other shift because the synchros are working a little harder. I have driven 3 different trucks with zf's, and some will delay more than others, but there is a definite difference between this 1-2 shift than any of the other gear changes. Mine will grind a little bit sometimes when cold because I have 10w30 oil in it.

It is a much larger gear spread. Mine does not grind, but I can hear the syncros wind up on that sift. I would imagine that its harder on them, so they wear out faster.
PZ

Mine would grind with mercon v in it. Not so much so with the MTL. Think i'm gonna change the shifter bushings tommorow and refill with some cheapo mercon and see what happens. I'd wanna check to see if theres any metal in the fluid again with as many times as i've crunched 2nd and reverse.

I don't know if you have read about it, but reverse popping out is another common problem with the zf's. When putting it in reverse, you need to keep pressure on the gear shift lever and slowly let out on the clutch. 50% of the time you will feel the lever go back a little more as it's not completely engaged. If you don't do this, 50% of the time the gear lever will pop out instead of the truck moving in reverse, and boy talk about a grinding noise.

Of course all these problems are more or less pronounced depending on the condition of the tranny.

itsacrazyasian said:

Gotta shift slow on the 1-2 shift when its cold. Going from 3-2 or 2-1 is fine no grinding. Before i tear this box apart to throw some syncros at it what do you all think? Should i try royal purple atf? Syncromax?

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I am going through the same thing myself.

I am not saying it's the proper fix for it, but as a commercial driver I learned to not try and shift until the RPS's are just about matched to where the gear needs the engine to rev to just slide in.

What I am trying to say is float the gears like you are not using the clutch, BUT USE THE CLUTCH!! lol. This saves a LOT of wear on the Synchros....kind of making them useless.

I just take my shifts really slow, but firm. It eliminates the grind between first and second.

Not that it is related to the grinding, but what clutch did you use and how do you like it?

Mine grinds btween 1st and second as well.I only use it to take off with a trailer, otherwise I just start in second. Much easier and less if a gap between gears.

When I first got my truck I used to use a little blip of throttle between 1st & 2nd to smooth things along, or do as Goofy Exponent suggests and hold a little pressure on the shifter up against 2nd and let it slide in (using clutch also) at its own pace. These days I rarely use 1st at all unless I'm sitting stopped on a hill. I was reading the ZF manual a while back and they reccomended starting out in second most of the time unless you are hauling or towing. We have so much torque to work with on these engines that my 2nd gear starts are easily as smooth as my 1st gear starts...

Goofy, i got a lifetime special from the local parts store. Said perfection on the clutch but its a Valeo unit in the box. Cost me 375 with a SMF. I like the clutch so far. I've owned SEVERAL ZF5's, the last one was a 89 F250 with a zf5 and it never shifted like this.

BTW i put mercon in it and took it for a ride. SHIFTED LIKE CRAP. Ordered up some MTL to dump back in it. Now i'm going home.

Also i had a problem with it coming out of reverse. Took the shifter apart and saw the nylon bushings had worn spots into the pivot. Sanded them smooth, installed an aluminum washer between the two to take up slack and reverse is not a problem anymore. I could see where i would bottom out the shifter before it was fully in reverse.

itsacrazyasian said:

Also i had a problem with it coming out of reverse. Took the shifter apart and saw the nylon bushings had worn spots into the pivot. Sanded them smooth, installed an aluminum washer between the two to take up slack and reverse is not a problem anymore. I could see where i would bottom out the shifter before it was fully in reverse.

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I got this same thing happening. It only happens when I am in reverse and I am bouncing a little....it might pop out.

I drained the mercon out and put redline MTL back in. MUCH MUCH improved. I can drive almost normally again. I guess i'm gonna need to do some synchros in it if i want it any better.