ZF5 won't stay in reverse!

[fiverpuller]

I finally fired up the Limo with the 6.9 transplant done and was just playing around a bit in the driveway and the tranny won't stay in reverse? Even if I hold the shifter down it pops straight out and grinds gears. I have no idea how these things work so I don't know where to start. Is this a common problem at all? I don't see how reverse could wear out. Could I have got the shifter installed incorrect? About every 10th attempt it will stay in and I can back up. Otherwise it won't even move the truck. Only put it in reverse once before the transplant and it didn't pop out then. I am about ready to take my shotgun to this thing...lesson learned about buying site unseen.

 

[towcat]

contrary to popular myth, ZF reverse gears have no syncros. they are straight cut gears. If reverse is popping out, chances are the needle bearings in the idler gear are shot. As a last ditch, refill the trans with 30wt and see what happens.

 

[Agnem]

Diag chart for the ZF5

 

[fiverpuller]

I will drain the oil and check for metal at least.

Mel...nice link. You saved me lots of time and effort searching for that.

 

[fiverpuller]

Towcat...check out page 15 of the link Mel sent. Especially item #67..."Reverse Gear Synchronizer Ring". Not trying to flame here ...just curious if I am only shifting past a syncro and not actually locking into gear. Plus it doesn't look straight cut so does this mean the helical cut will help the gear "lock" in under pressure?

I really need to see pictures of the inside of one of these...I just don't want it to be mine. ;p Once again...thanks for the awesome link Mel...I am in a much better mood tonight since I didn't get all greasy wrenching.

 

[towcat]

Towcat...check out page 15 of the link Mel sent. Especially item #67..."Reverse Gear Synchronizer Ring". Not trying to flame here ...just curious if I am only shifting past a syncro and not actually locking into gear. Plus it doesn't look straight cut so does this mean the helical cut will help the gear "lock" in under pressure?

I really need to see pictures of the inside of one of these...I just don't want it to be mine. ;p Once again...thanks for the awesome link Mel...I am in a much better mood tonight since I didn't get all greasy wrenching.

I stand corrected. I've never changed one out on a ZF. The rebuild kit comes with the syncros for the forward gears and the bearing kit. If I didn't have to fight with one, I certainly didn't go there. The problems always started with 4th since that gear was not supported like most trannys. never heard of a problem with reverse outsie of the idler gear needle bearings.

 

[fiverpuller]

Towcat, sounds like you know a bit about the ZF tranny. I think it's time for a rebuild. Pretty much every gear makes a good whining sound except 4th. This kinda tells me that the countershaft has issues? If there is some bad bearings I want them fixed before the gears wear....right?

Also I have determined the reverse gear syncro does not line up the gears all the time. It's about 50/50 now going directly into reverse. The times it doesn't I just slip the clutch a little...the gears grind a little...then it drops in all by itself. This is very annoying. When I drained the fluid there was not much metal down there. The biggest piece being maybe 1/16" long...and only a couple of those.

Looking at the diagram the reverse syncro comes in a sub-assy with the 5th gear syncro. Is there such thing as a rebuild kit for these that includes all bearings and synco packs? Or do you just replace things as needed. I just want to have this thing dialed in for another 213k miles. And is this something a garage hack like myself do without special tools or training? I read there is some preload stuff that kinda scared me. Sorry for rambling...it's Friday.

 

[towcat]

Just for S&G, drain the oil out of the trans(it "should" be ATF) and fill with 30wt. officially its a nono, but it helps worn out trannies for a little while. You should be able to convince any trans shop in your area to sell you a rebuild kit, but its an item you do not want to tackle by yourself. When I am in CA, I help manage a trans shop for a friend of mime an even I won't put one of these trannys back together. He gets the ugly job of doing so.
Wait a minute........did I read somewhere you flattowed this truck? Tell me that you did pull the driveshaft(s) if you did so.......

 

[fiverpuller]

Yeah I pulled the rear driveline. Otherwise 950 miles at 65mph would have killed it for sure! Left the hubs unlocked and put tranny in 1st just in case the front driveline wanted to spin a little.

So no beans on the do-it-yourselfer eh? Maybe just the T-19 is an easy rebuild? Guess I will just run it this way for a while and see if it gets worse. It's not a real bad whine but noticeable with the windows up. Shift boot is pretty torn up. I bet if I put a new one on or add some insulation to it the noise will not be heard. I am just a little worried about towing in 5th.

 

[towcat]

T-19 and the ZF5 are completely different animals. I have no problem with doing a t-19, but the ZF is completely out of my league. Run with the 30wt for a while and that should help cut down the noise and maybe the problems. All work trucks with worn out ZF's, get motor oil. It doesn't render them unrebuildable at all. ATF is good for the syncros that aren't worn out. There is a "sintered metal" deposited on the cone side of the syncro to help slow down the gear sooner. But if the stuff is worn down, it doesn't matter much anymore on what oil you use at this point. i've gone as far as putting in 40wt. before pulling the trans out for replacement.

 

[fiverpuller]

I've got absolutely no problems with the 1-5 syncros...only reverse has issues for whatever reason. It sounds like the whine is no big issue...just a high mile tranny. Possibly a "Worn input shaft gear and countershaft drive gear" from the troubleshooting guide. But at this point I will stick to the "if it ain't broke don't fix it" motto. And if the syncros give me trouble down the road I will toss in some 30w. Thanks for the comments.

 

[towcat]

If your dust boot in the interior is ripped, do yourself a treat and get the new assy from the stealership. you get the upper and lower boots, the plastic retainer and screws. dunno what the inner rubber material is, but it sure cuts down on the noise coming fromt he trans.

 

[John Deere]

I had this problem in one of my zf5's, it was the syncros on the reverse gear were worn out. I did the rebuild, it is fairly simple if you have a little mech. experience.

 

[fiverpuller]

Interesting...so maybe if you don't replace the bearings you don't have to reset the preload because it will already be set? Just swap syncros and reassemble? I might have to take a peek inside when I do the flywheel. This not going into reverse issue is starting to get annoying.