6 Speed trans conversion?
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Tuned
Joined: Mar 2007
Posts: 254
Likes: 0
From: Sacramento Ca
6 Speed trans conversion?
Hello all;
It's been a while since I was around here but I have a question or two. I think I am losing the first and second gear syncros in the ZF5 speed in my 95 F350 w/ 7.3. Given I am going to have to pull the trans and put $$$$ into it, I was thinking the 6 speed used on the newer trucks would make a nice upgrade. Gaining a little more OD for the freeways would be a nice benefit.
Has anybody around here done this before? How difficult is it? Is there a conversion kit available for any of the odd parts needed? Is it a simple bolt in?
Any other thoughts or questions?
It's been a while since I was around here but I have a question or two. I think I am losing the first and second gear syncros in the ZF5 speed in my 95 F350 w/ 7.3. Given I am going to have to pull the trans and put $$$$ into it, I was thinking the 6 speed used on the newer trucks would make a nice upgrade. Gaining a little more OD for the freeways would be a nice benefit.
Has anybody around here done this before? How difficult is it? Is there a conversion kit available for any of the odd parts needed? Is it a simple bolt in?
Any other thoughts or questions?
Senior User
Joined: Oct 2013
Posts: 259
Likes: 0
From: Southwestern, Ontario
The ZF6 doesn't really add much OD benefit as the gear ratios are just closer together if I remember correctly. There might be a bellhousing to mate your 7.3 to a Tremec Magnum (or a TR-6060 or T56 if they have the torque capacity), but its usually in the $3000 price range for those transmissions. I'm not good with autos, but I believe most of the 6 speeds require a control module if available at all. Those will likely be pricey as well. It would be cool to see someone make the swap though.
Laughing Gas
Joined: Mar 2006
Posts: 1,164
Likes: 2
From: Tri-Cities, TN
I know the bell needs to be modified at least. I did some research into this when I got my truck - the ZF-6 is relatively common in yards around here - and I couldn't even come close to justifying the cost vs. any potential fuel savings. Of course, there was nothing wrong with my ZF-5, so I would have just been doing it for the small OD improvement. Maybe it's more reasonable if you have a trashed transmission you need to replace as the actual cost for the tranny isn't outrageous.
Lead Driver
Joined: May 2011
Posts: 5,772
Likes: 442
7.3 zf6 will bolt right up.
Zf6 vs zf5 is night and day difference in drivability with the extra gear, and mileage is noticeable if you do a lot of accelerating vs highway driving.
Zf5s have a garbage 3 acceleration gears, 4 is a huge difference.
You'll need tunnel mods, but way worth it IMO.
Zf6 vs zf5 is night and day difference in drivability with the extra gear, and mileage is noticeable if you do a lot of accelerating vs highway driving.
Zf5s have a garbage 3 acceleration gears, 4 is a huge difference.
You'll need tunnel mods, but way worth it IMO.
Thread Starter
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Tuned
Joined: Mar 2007
Posts: 254
Likes: 0
From: Sacramento Ca
I know the bell housing will work just fine as they were factory from 99 to 2002 behind the 7.3. That is the easy part. I am more concerned about things like cross members, drive line length + yoke compatibility, speedo drive, an shifter location.
These are the big questions for me.
When "tunnel mods" are mentioned, What is meant by that?
These are the big questions for me.
When "tunnel mods" are mentioned, What is meant by that?
Cargo Master
Joined: Mar 2010
Posts: 3,326
Likes: 292
From: Laramie, WY
Your speedometer is dependent on the VSS, located in the rear axle, so nothing to worry about there. I read on a diesel site that you'll need to run a SD clutch, due to input shaft differences between the OBS ZF5 and SD ZF6. Also that you'll need a different cross member, but no details there. I'm sure others (those experienced with the swap) will fill in the rest.
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Lead Driver
Joined: May 2011
Posts: 5,772
Likes: 442
You'll have to cut the trans tunnel out and make it bigger to install the towering zf6.
Remove seats and carpet, cut trans tunnel out across the length of the trans, install zf6, build new tunnel around trans.
Remove seats and carpet, cut trans tunnel out across the length of the trans, install zf6, build new tunnel around trans.
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Thread Starter
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Tuned
Joined: Mar 2007
Posts: 254
Likes: 0
From: Sacramento Ca
I am hoping for just this.......
Fleet Owner
Joined: May 2009
Posts: 21,437
Likes: 76
From: Gilbert, PA
You will need a T-Case from a MANUALLY shifted truck and from behind a ZF6
The auto trans t-cases use a different spline than ZF6
Also, have you priced a ZF6?!?!? Yards around here get 2k for one
A FULL rebuild on your ZF5 around here is under $500
The auto trans t-cases use a different spline than ZF6
Also, have you priced a ZF6?!?!? Yards around here get 2k for one
A FULL rebuild on your ZF5 around here is under $500
Lead Driver
Joined: May 2011
Posts: 5,772
Likes: 442
It all depends on what kind of access you have to parts. I've gotten two zf6 for literally 130 bucks a pop at you pull jy ' s, they're in the business of scrap with part sales being icing on their cake. Part recyclers are going to charge a lot more for anything, just cuz they can. Their volume of zf6 and local demand will dictate what they charge
I've also gotten wrecked trucks for 3-4k, after selling everything it's a free trans and misc parts.
I've also gotten wrecked trucks for 3-4k, after selling everything it's a free trans and misc parts.
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