Well heck, this just got interesting. I know people have used the word "noisy" before, but this sounds like a bit more than just noisy.... Overdrive better save you some serious pennies at the pump to make this all worth it!

I agree on the embarrassing part and feel for you. I've been chasing down clunks and rattles for a while now and am narrowing in on a completely noise-free truck. I also don't like getting that "look" at a red light lol.

 

I am going back and rechecking all the clutch components, flywheel, replacing the spacer plate with one for a manual, new t.o. bearing and pilot bearing, new slave, etc. and checking the clutch forks to make sure the 'growl' was not coming from any of those.

*I also wanted to restate this for those reading this thread, to help with their own zf install: The manual trans expert at the shop said, 'the zf5 is notorious for being noisy. You can put it behind one engine and it'll make all kinds of noise. Put it behind another and it'll be quiet as a lamb. They tend to be noisy with engines with a big cam, and those idling slowly.'

That being said, I did notice that the noise disappeared with a bit more rpm. Would I have done this install knowing it was going to cost way way more than expected? And still end up with a loud, rude transmission noise? No! But now, with the driveshafts changed and the c6 sold, etc, I'm committed.

Hope that helps. I am adding an extra layer of carpet pad under my carpet to help block the noise. Actually, I'm hoping that by changing the t.o. bearing to Timken, and changing the spacer plate to a manual type, changing the pilot bearing as well, I will eliminate the growl. We'll see.

I am old school and when a trans is growling as it did, I think: something ain't right. But, the trans shop put it on the dyno, and opened the case, and all was peachy, according to them, so here I am. I am rethinking my long-held high regard for German engineering. I guess it does take a great design to growl alarmingly, and not fly apart!!!!

 

I noticed that the Timken t.o. bearing looked much better quality that the one I had in it. Timken is on the right.

Attachment 283561

I changed the slave cylinder as well, and used AMS via RockAuto. It is made in Germany, and came with impressive packaging.

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I swapped the pilot bearing too. For $15 I could not not change it. The clutch, which is a Ram clutch for a 351 looked good.

To help with the installation, I took two old head bolts and cut the heads off, cut a slot in the shaft for a screwdriver, and screwed them into the trans mount holes in the block. The really helped with alignment. I was able to slide the trans onto them, and then just push it forward.

 

Thanks to the member(s) who recommended using a synthetic ATF in the trans, and to fill it one quart over the recommended amount, filling it through the shifter tower. I had been using cheap STP ATF, and I'm very curious to see if the new fluid, along with an extra quart, will quiet down the growl I experienced before. I[m now trying Redline D4.

 

Fingers crossed this works well!!!

 

OMGosh! The truck, the four month project, is finished. The growl is still there with the trans, but is subdued. I don't know if that is due to the extra layer of carpet I added as sound barrier, or from changing some of the components. Anyways, I am driving it! And it is impressive with the new engine and the large cam. It pulls strong and hard in every gear, although I'm yet to try 5th OD.

Attachment 282140

Attachment 280913

One funny thing is that with the header and 2 into one 3" exhaust, into a flowmaster 50, when I wind out the gears, after about 3k rpm, it makes a drone like a Honda with modded exhaust. Me no likey. But for a while I'm tired of messing with it.

The collectors (above) had a terrible exhaust leak even with Remflex gaskets. I took out the RF gaskets, added copper gaskets and a bead top and bottom of Red high temp gasket permatex. Seals like a dream.

 

Carburetor Adjustment: Another aspect of a c6 to manual trans is one no one speaks about. That is that it requires a carburetor re-calibration. I had a .034 acc. pump squirter nozzle in the Holley 1848 that I ran with the c6. After a terrible stumble when starting out, I began re-calibrating the acc. pump shot by changing the nozzles. I read online that a manual traditionally requires less of a acc. pump shot off the line, so I began dropping down the recommended .003 increments and test driving with each change.

I ended up with a .025 squirter, and had to change the cam position from #1 to #2 with the screw.

Now it is a joy to drive, and the final fine-tuning can wait until I get the air/fuel ratio gauge hooked up. I just wanted to post this so others making the swap will know in advance that a dialing in of the carb will most likely be needed.

 

After driving around town a bit, I've realized that this transmission has turned my truck into a road obstacle. The 3rd gear synchros must be worn and prevent a smooth shift into third. I loose acceleration during the pause, and cars speed around and honk! There is also a LOUD rattle from the trans when up shifting and accelerating hard in a new gear. There is no smoothness in acceleration.

I hate this transmission as it is!

Let this be a warning to those putting in a used and unknown ZF. I even had a shop split the case and examine it!!

Now I am thinking of whether to have it rebuilt or dip into he bank and just go with a new, modern TREMEC.

 

6-speed Tremec + 300 I-6 combo.... que the Homer Simpson drool....

 

LOL! Hey Aaron. I don't know if I'd go with a 6 speed, but right now I'm not ruling it out. What I don't want is to spend another $1-2,000 on this loud, clunking dinosaur, and end up with a loud, clunking dinosaur of a trans.

 

Fair enough! I'm happy that you've posted all your progress, challenges, and even the complaints. The ZF-5 often comes up as the "king" of upgrades for a standard trans on these forums - no different than the Eldorado Calipers for brakes. It's great to know that the grass isn't always greener because I feel as though a lot of folks don't post up the true information like you have.

Kudos to you for taking the risk and the time to do all this work and to admit you don't like it. Nothing wrong with that in my books. And thanks for sharing along the way!

 

Please keep in mind that the trans I have, in the state it is in, may be far different than the noise level and shifting ability of a rebuilt or properly working ZF5. I have a long pause when shifting into 3rd. I'm sure that is not 'normal.' I also have a terrible noise that I assume is needle bearings? Couple that with the fact that I was trying to dial in my Holley carb so it wouldn't stumble at take off, and you get a horrible driving experience with people shouting at me!

I have a forum buddy with a freshly rebuilt zf5, and he says he shifts with two fingers and flies through traffic, always ahead of the pack. So ... two very diff. trans. Two very different driving experiences.

 

Very interesting that I read here ZF S5-42, S5-47 Transmission Specs & Ratios in the specs chart footnote, that 'zf5 equiped vehicles are equiped with a dual mass flywheel to suppress engine harmonics and resulting noise through the transmission!!! Where the *&# was that info when I was thinking about installing one?????????

To anyone considering a ZF5: They can be noisy to the point of making you hate to drive the vehicle it is in. Having the OD, however, means being able to drive with the flow of traffic at 75 mph, and to feel completely safe, at a relatively low rpm, while doing so. Apart from the sometimes exasperating noise, the zf has brought my truck up to a new level. I am curious now about the mpg after a long trip on the freeway.

 

One of the last things I needed to do with my ZF was recalibrate my speedometer. I downloaded a miles per hour app to check my mph, and I was traveling about 10 mph faster than my speedo said. Recalibration is very simple. Only one 7/16" bolt holds the speedo cable to the trans tail housing. I removed that and pulled out the cable.

Attachment 283247

Above is the one that came on the trans. That plastic gear is the one to change. Only a simple metal clip holds it on. Pop off the clip with a small flat blade screwdriver, and the gear slides off. I changed from a 20 tooth gear to a 19 tooth one, and that produced a 3 mph change. Smaller or gear with fewer teeth make the speedo spin faster. Larger gears or those with more teeth, make the speedo spin slower. Because I saw a 3 mph change, I calculated that I needed a gear with 17 teeth. Here is a site that sells the gears new: https://transmissioncenter.net/shop/...ransfer-cases/ But I'm a cheap skate and found a used one on ebay for a fraction of the price.

*Note for those thinking of installing a used ZF5. I did, and regretted it. It is soooooo loud when I accelerate in 2nd and 3rd that I'm afraid residents in the houses on the street will come out and shout at me for disturbing them. A trans that makes noises like that, imo, can't be long for this world. So, I'm taking it in to have it rebuilt. I was told that a starting price was $800, labor and materials, and that would go up if gears, shafts needed to be replaced.

 

Now that I've been driving it for some months, the machine gun sound the trans makes when accelerating in third gear has driven me loopy and I'm pulling the trans to have it rebuilt. The shop wants only $600. They only replace the bearings and seals, etc., not the needle bearings for that price. I told them to replace the needle bearings too, and they said extra $100. For $100 why would anyone NOT do it? Timko bearings.

I'm thinking about doing the short-shift mail in conversion for $300. It takes forever to shift with this thing.

The growl it made when I first installed it, has diminished to nothing. But all the action of the clutch is in the first 2" of travel, so I've decided to cut off the end of the clutch rod, thread it, and install an adjustable heim joint with a lock nut.

The best aspect of the trans swap is the jump in mpg. I was pleased to find that I was getting just over 20 mpg on a recent trip. I am looking forward to installing my Quadrajet with the APT (adjustable part throttle) that allows me to minutely move the metering rod up or down in the jet, according to what the AFR gauge says, and dial it in to produce ultimate mpg. It still strikes me as odd to put a 800 cfm carb on a 307 ci engine, but hey, gm put the same carb on 230 ci v6's! Variable cfm carb.

Attachment 282321

Above is the end I'll be cutting/threading.

Attachment 282322