How hard is it to rebuild the Zf

Dieselguy123 · May 25, 2007

Hey all, I am glad that I ended up not selling my zf, I got my truck on the road the other day and it has a ton of power but the rpms are just to high, I would like to take full advantage of the fuel economy, I think that the one I have needs bearings and syncros, Is this a job a compitant "backyard mechanic" can do or should I leave it to someone with a little more expeirance? I feel totally comfortable tearing into somthing like this but I just wondered if there where any things that I would run into, I would like to do it myself to save the $$$$$ it would cost to have it done,(Unless someone has a gearvendors just laying around they would part with

) Thanks-Brad-

tonkadoctor · May 25, 2007

It's a PITA but you can do the bearings and races in a home shop. The syncros would be best left to a good shop that has the tools to get the gears and syncros off of the mainshaft.

When I did mine I had to take the case into a transmission shop to get one race removed that I couldn't find a puller for and the trans shop ended up grinding one of their tools to fit. Had them clean the case and tailshaft housing while they were at it and it was $35 for everything....money well spent. I would have had them do the syncros too if I needed to go that far.

On the ZF5 the entire gear cluster is attached to the tailshaft as well as all of the shift rods so when you pull it you will get the entire guts of the tranny in one nice 200 lb chunk

A few things to watch out for.

when you pull the shifter there is a spring and a small metal piece just under it. Pull them out and set to the side.
the syncro between the input shaft and mainshaft is easy to pull apart while you are looking at stuff and trying to figure out how it goes together...If you pull apart a syncro you have 9 small pieces to worry about losing, 3 detent balls, 3 springs and 3 detent ball holders......It's all spring loaded and they will fly all over the shop (don't ask me how I know, I'll just say it took me 2 hours to get that one syncro back together)
before separating the case from the tailshaft housing .....On the side of the case towards the rear and on the tailshaft housing there are 2 allen head bolts, remove the one on the case. These 2 hold the reverse idler shaft, remove the one from the tailshaft after separating the halves so the whole gear pack comes out nice and clean.
On the top of the case by the bellhousing there are 3 freeze plugs that are prolly covered with silicone. Under them are springs and detents for the shift rods. The transmission will come apart with these in place put you will have to remove the plugs and springs and move the detents out of the way to slip it back on when putting it back together. You will probably not be able to get the detents out as the top of the holes have been swedged(for some reason I think that's the wrong word but CRS is kicking) to hold the spring loaded freeze plugs in place, just keep them back when handeling the case for final assembly.

IIRC I bought my rebuild kit at Autozone, the bearing and seal kit was about $190. They also have a kit that includes syncros for just under $400. I think the kit at advance auto parts was about $700 as are a few others I looked at.

Cheaper Jeeper · May 26, 2007

I have a good used 2WD ZF-5 S42 that I'd sell you for a lot less than a rebuild. Only trouble is we're 2000 miles apart.....

Dieselguy123 · May 26, 2007

Well, I am not really sure what is wrong with this one, it goes down the road ok and shifts well through all the gears but it is just a PITA to get into reverse. Tonka, you mentioned somthing about a spring and a little metal piece under the shifter assembley......I know that mine doesnt have one, What exactly does it do, could this be part of my problem? Do the syncros in the zf have that fiber coating or whatever it is that will be eaten away by gear lube or motor oil? Thanks for the help -Brad-

tonkadoctor · May 26, 2007

Dieselguy123 said:
Well, I am not really sure what is wrong with this one, it goes down the road ok and shifts well through all the gears but it is just a PITA to get into reverse. Tonka, you mentioned somthing about a spring and a little metal piece under the shifter assembley......I know that mine doesnt have one, What exactly does it do, could this be part of my problem? Do the syncros in the zf have that fiber coating or whatever it is that will be eaten away by gear lube or motor oil? Thanks for the help -Brad-

I never studied what the spring and metal part was for but I beleive it is for the reverse light detent, I just set it to the side as soon as I discovered it so I wouldn't lose it.

The syncros are a composite friction material like on a clutch and are bonded to the inside of the metal syncro rings that the shift forks ride on. You should be running ATF in the ZF5 tranny. I don't know what kind of effect gear or motor oil will have on the friction material.

Here are a couple diagrams that show the location of the specific parts I mentioned in my previous post. I pulled the originals I edited and blew up off of www.drivetrain.com They also have the part list to go with the numbers.

I ain't no expert on this tranny but I'll help you as much as I can and share what I learned mostly the hard way -cuss

....

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sle2115 · May 26, 2007

Wish I had one, I would probably give a rebuild a go. Have done quite a few manuals, the T86AA (and others) uses a similar check ball and dog synchro setup and is not all that bad. You can generally assemble all the pieces and then slide things together.

Rawpower · May 26, 2007

tonkadoctor said:
the syncro between the input shaft and mainshaft is easy to pull apart while you are looking at stuff and trying to figure out how it goes together...If you pull apart a syncro you have 9 small pieces to worry about losing, 3 detent balls, 3 springs and 3 detent ball holders......It's all spring loaded and they will fly all over the shop (don't ask me how I know, I'll just say it took me 2 hours to get that one syncro back together)

Haha, besides us... wonder how many other people have learned that the hard way? I couldn't get mine back in, I just decided that the rebuild was something I wasn't up to par for. But I got a shop around here to rebuild it for $500, looks like that turned out to be a hell of a deal.

Also, I think that piece with the spring might be for the shifter guard thing that pevents you from going from any gear to R and vice versa w/out releasing the catch by allowing the shifterstick to recenter... does that make sense?

tonkadoctor · May 26, 2007

Rawpower said:
Haha, besides us... wonder how many other people have learned that the hard way? I couldn't get mine back in, I just decided that the rebuild was something I wasn't up to par for. But I got a shop around here to rebuild it for $500, looks like that turned out to be a hell of a deal.

Also, I think that piece with the spring might be for the shifter guard thing that pevents you from going from any gear to R and vice versa w/out releasing the catch by allowing the shifterstick to recenter... does that make sense?

I ended up putting some really thick John Deere implement grease on those parts to try to hold them in place....The next 100 times they flew out they stuck where ever they first landed making them easy to find.

$500 was a good deal. The major expense in a rebuild is the labor getting the tranny out and back in. A good experienced transmission mechanic can tear one down, clean it up and slap them back together in a couple hours on the bench.

It could be a reverse lockout, that makes sense. Somebody else will have to fill us in on it's function.

Dieselguy123 · May 27, 2007

Thanks for all the input guys, Tonka, thanks for the diagrams, I am still not sure which route I will go but I have a better idea now, thanks again -Brad-

mechanoman · Jan 17, 2008

Man alive, you guys are right on the money. I had to change the back case and thanks to the good advice everything went great. When it got around to changing the races, one was easy but the other was in a blind hole and I couldn't get anything behind it to knock it out. Since the old tail case was already toast (one of the trans mount feet had been broken off) I just took the Bridgeport and cut a hole through the back of the old case. Crude but effective. Everything else was smooth until I got around to that top synchronizer. Yeah, like a ******* I took it apart. Didn't lose any of the pieces, but how the heck do you get the springs and balls back together? I took the whole affair into the shop's shower stall, covered the drain, and closed the shower door. No matter where the springs and balls fly to, I can find them. I'm an old timer, but darned if I can figure out how to get them back in. Anyone know of a neat trick?

tonkadoctor · Jan 17, 2008

mechanoman said:
Everything else was smooth until I got around to that top synchronizer. Yeah, like a ******* I took it apart. Didn't lose any of the pieces, but how the heck do you get the springs and balls back together? I took the whole affair into the shop's shower stall, covered the drain, and closed the shower door. No matter where the springs and balls fly to, I can find them. I'm an old timer, but darned if I can figure out how to get them back in. Anyone know of a neat trick?

Nice thick heavy grease to try to hold them in place and a lot of patience and 3 extra hands. There is prolly a special tool for this but I was able to do it the hard way by myself...... After a couple hours of "practice" ;Pissed

At worst the grease will let them stick on the first bounce when they fly out.

mechanoman · Jan 17, 2008

ZF-5 synchronizer reassembly woes

Yup, that grease trick works pretty good but I am so frustrated that I said the heck with it for today and will try it again tomorrow. -cuss

There must be some kind of tool that makes this job do-able, I just can't imagine what it would look like. cookoo

Anyhow, it will all look better in the morning, thanks for your reply. :thanks:

mechanoman · Jan 17, 2008

Got it!

tonkadoctor said:
Nice thick heavy grease to try to hold them in place and a lot of patience and 3 extra hands. There is prolly a special tool for this but I was able to do it the hard way by myself...... After a couple hours of "practice"

At worst the grease will let them stick on the first bounce when they fly out.

Hey tonkadoctor, I owe you a cold beer! Finished supper but was still bugged about those #$%& sychronizer balls and springs. Went back to the shop and put all three in in about 5 minutes.

Used some good stiff grease and stuck the spring into the hole towards the center of the mainshaft where it seated and was sitting horizontal. Then I stuck the little ball into the center hole of the plate with plenty of heavy grease to hold it in place. Slid the plate and ball down the groove until it was resting on top of the horizontal spring. With left hand keeping gentle pressure on top of the plate, I used a scribe point to compress the spring by pushing the outer end of the spring towards the center of the mainshaft just far enough to let the plate slip by. Voila! When the plate slid down past the end of the compressed spring the ball seated perfectly into the end of the spring. Repeated this procedure twice more, cleaned up and turned out the shop lights with a big grin. Thanks, pal... I owes you one! ;Sweet

BigRigTech · Jan 17, 2008

If you can't get a bearing race out then run a heavy bead of weld with a MIG around the entire inner circumference....The bearing will shrink and pretty much fall out. Works great on wheel hub races and etc.

riotwarrior · Jan 17, 2008

BigRigTech said:
If you can't get a bearing race out then run a heavy bead of weld with a MIG around the entire inner circumference....The bearing will shrink and pretty much fall out. Works great on wheel hub races and etc.

Now thats a tip I forgot I was told years ago.....I saw a fellow do that once and was amazed...I was bout 15 or 16 I think so um...ya I forgot all bout that.

Thanks for the reminder

How hard is it to rebuild the Zf

Dieselguy123

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