ZF5 rebuild

[gunnibronco]

I'm pretty sure my ZF5 needs to be rebuilt. It was a Craigslist score, that looked very clean and it was cheap enough so I bought it.

After my install, it leaked (badly) out of the front seal. I pulled the case apart and added a "Speedie Sleeve" and it sealed up. Since then I've had problems with it griding into gears despite the clutch pedal completely depressed. This happens on upshifts and downshifts as well as going into reverse or going from reverse into 1st or 2nd.

It rarely, but sometimes slightly grinds/buzzes into gear in 2 Hi. I can usually shift as quickly as I want in 2 Hi without any problem, but sometimes I can feel & hear slight gear grinding.

In 4 low 2.7:1 (Atlas 4 speed), I get more noticable grinding, when I shift quickly.

In 4 low 4.3:1 and low/low 11.7:1, I have significant difficulty making a clean up shift or down shift. If I let the motor completely wind down I usually can avoid grinding. This doesn't really work for offroading as the shifts have to take so long the truck will come to a complete stop before I can shift into the next gear.

I'm assuming this indicates bad synchros and/or bearing play making gear alignment slow/impossible. Is this a correct diagnosis? I assume the transmission shouldn't do this and I should be able to make fairly quick shifts (not looking for race car performance) without grinding gears.

Can anyone recommend a good source for a rebuild kit? I see a wide range of pricing and want to buy quality as the work will obviously be significant. I do have people familiar with rebuilding transmissions available who will help, I know the ZF5 is a somewhat difficult transmission to work with.

Thanks

 

[Timmy390]

What fluid are you running?

Tim

 

[Bitch'nBronco]

Take a look at this video, it does not look like a fun rebuild

Dave Chappelle from Dirt Everyday just swapped 4 qts of Redline MT90 into his ZF and it solved the grinding into gear issue and stopped the bearing rollover noise. I'm going to do the same when I put mine back into the Bronco. From what I've read, the ATF from ford was originally recommended by ZF for cold climates, and was originally a gear oil for regular/hot climates.

As far as kits go, this is the one I've seen recommend in OBS forums https://www.usastandardgear.com/sho...jBocVFYVRSC_vM9Wpj0BlIMGlV7PXxn_8m-5O6YLb9fCf

 

[gunnibronco]

What fluid are you running?

Tim

Synthetic Valvoline ATF. Is the stuff recommended below better or something else?
edit: I just saw the Valvoline Synthetic ATF is approved as Mercon LV, not Mercon V. Is LV low viscosity? and could that be the problem?

Take a look at this video, it does not look like a fun rebuild

Dave Chappelle from Dirt Everyday just swapped 4 qts of Redline MT90 into his ZF and it solved the grinding into gear issue and stopped the bearing rollover noise. I'm going to do the same when I put mine back into the Bronco. From what I've read, the ATF from ford was originally recommended by ZF for cold climates, and was originally a gear oil for regular/hot climates.

As far as kits go, this is the one I've seen recommend in OBS forums https://www.usastandardgear.com/sho...jBocVFYVRSC_vM9Wpj0BlIMGlV7PXxn_8m-5O6YLb9fCf

I'll look up the Dirt Everyday video. I found it on his Dirthead Shed page. It would be great to just swap oil.
Thanks for the rebuild video, I'll check it out. I have read it is a difficult rebuild, but I have some very experienced friends willing to help. Hopefully a fluid swap will avoid the rebuild. Thanks.

 

[Timmy390]

Redline MT90 is good stuff. I run "synchromesh" in my M5ODR2 and it shifts good.

Your issue sounds like a fluid issue to me. I would give the proper fluid a try before I rebuild it.

Tim

 

[gunnibronco]

Redline MT90 is good stuff. I run "synchromesh" in my M5ODR2 and it shifts good.

Your issue sounds like a fluid issue to me. I would give the proper fluid a try before I rebuild it.

Tim

I'll check Synchromesh out and will definitely swap fluids before attempting a rebuild. Glad I asked here before tearing into the trans. I agree it feels like a thicker oil would help.

Thanks

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[phred]

I’m running redline MTF. The roll over noise is bad but it shifts just fine. I had the zf rebuilt about 5000 miles ago. Everything in it is new except the main shaft. I’ll probably change to mt90 at 10k to help quiet it down some.

 

[gunnibronco]

I’m running redline MTF. The roll over noise is bad but it shifts just fine. I had the zf rebuilt about 5000 miles ago. Everything in it is new except the main shaft. I’ll probably change to mt90 at 10k to help quiet it down some.

I've ordered the MT90. I'll update when I get it swapped in. Thanks for the info.

 

[Bitch'nBronco]

I've got the bottles of it ready to go. I want to redo my trans tunnel so you'll probably get a chance to try it out before I do.

 

[gunnibronco]

I drained the trans and refilled it with MT90 and took it for a quick test drive. It shifts better and grinding was greatly reduced, but not totally eliminated.

It seems it's shifting very well between 2nd and 3rd, even in the 4 low gears (2.72:1, 4.3:1, and 11.7:1).

I'm still getting grinding between 1st and 2nd in the 4.3:1 and 11.7:1 low gears. I was testing it with a "worst case scenario" running the RPMs up around 3K and shifting quickly. Do I have unreasonable expectations of these types of shifts? There is a significant drop in gear ratio from 1st to 2nd (5.72:1 to 2.94:1), it does occur to me that it just won't shift quickly between those gears. I can modify my driving style to adapt if needed. I just don't have experience with any other ZF5 to know what to expect.

I've watched several ZF5 rebuild videos and it seems within my capabilities to rebuild it myself if needed.

Thanks

 

[gnpenning]

As you know these are truck transmission and not a race car type shifter. RPM, ground speed are important to a smooth shift. If everything matches you should be able to shift up and down the gears without the clutch. Yes, I know it's not for everyone or every shift, just reiterating the relationship of RPM and ground speed.

Drive any heavy truck with a manual you should be able run the gears and only use the clutch when stopping and starting out.

The end play should be measured before tear down and matched upon reassemble.

I don't know how fast you are trying to go through the gears, try slowing down and see what happens. It sounds like you are trying to row through the gears?

 

[gunnibronco]

That's my thoughts as well. This might just be what I should be expecting.

The transmission that's in question was a Craigslist score of unknown condition. I doubt it was ever rebuilt. I'm trying to decide whether or not to rebuild it. Obviously I don't want to do a rebuild if it's not going to improve the performance.

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