ZF5 with a US Gears O/D or a ZF6?

portlandareae28 · Jan 10, 2014

So the truck is going to need a trans rebuild or replacement soon. I currently have a ZF5 and an Overdrive. That means the truck ultimately has 2 different gear ratios 4.10 (the stock axles) and 3.23 the Overdrive gearing. I am wondering what you guys think about eliminating the overdrive and ZF5 for a ZF6 (overdrive is not compatible with the ZF6 or this decision would be easy) If I went ZF6 I would likely throw 3.73 or 3.54 axles under the truck.

Does the ZF6 have the gear roll over like ZF5 with a SMF?

Is there much difference in shifting quality? I have only driven Dodge 6spds

clutch options? The truck isn't a brute, but stock clutch definitely won't hold

Thanks for all opinions!!

Bobby@cp · Jan 11, 2014

I would stick with the zf5 and od

portlandareae28 · Jan 11, 2014

Bobby is there any advantage to the ZF6 other than I hear they can take a little more power?

m j · Jan 11, 2014

closer gear spacing due to the additional gear.
so less rpm drop on shifts, you might have noticed the ZF5 has one gear that has a little more rpm drop, i think the zf6 filled that hole

portlandareae28 · Jan 11, 2014

yeah I figured it was closer ratio. Are they any less noisy? (gear roll over)

Bobby@cp · Jan 11, 2014

portlandareae28 said:
Bobby is there any advantage to the ZF6 other than I hear they can take a little more power?

Read below.

m j said:
closer gear spacing due to the additional gear.
so less rpm drop on shifts, you might have noticed the ZF5 has one gear that has a little more rpm drop, i think the zf6 filled that hole

They might be able to take a little bit more power but IMO it isnt worth it.

Powerstroke Cowboy · Jan 11, 2014

Honestly for what you would gain I am not sure it would be worth it. If I was to do it again i would have just kept the ZF5 in. The ZF6 is nice and with 4.10 gears it would make a great combo for a tow rig. I have 3.55 and the ZF6 and can still pill good in OD just 4.10 would be more ideal for towing. Unless you can get the ZF6 cheap it honestly might not be worth it. Now that I have it I would not go back!!

Another thing with the ZF6 you will need to hook a cooler up to it. If you do not it will get hot towing! I found that out. It got so hot it did not want to shift the lever would almost not move! BUT I was bucking ahead wind and running through 5% grades. It comes down what do you really want?

Binder man · Jan 11, 2014

What did you do for your master to slave cylinder connection?

Powerstroke Cowboy · Jan 11, 2014

Binder man said:
What did you do for your master to slave cylinder connection?

The Factory ZF5 slave cylinder connector (the fitting is the kind you push in then push a pin through to hold it in place) Is the same as the one on the 99-03 ZF6 slave cylinder. So all you need for the hydraulics is the ZF6 slave cylinder. The line from the Factory 94-97 master cylinder connects right up. The OBS one hooks in at a 90* angle off the cylinder and the SD on goes strait in the back.