1977 F100 T18 to ZF5 transmission swap

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01-31-2014, 03:41 PM

tndallas

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1977 F100 T18 to ZF5 transmission swap

I've got a 77F100 302 long wheel base 2WD with a 4 speed T18 (not original) transmission that I've been investigating putting a 5 speed ZF5 into. I've done a lot of searching here and on the internet but still have few questions. I hope some of you can help.

1) I found a junkyard zf5 with 50k miles for $550. What is the likelihood that this transmission will have to be rebuilt in the near term?
2) I know I will have to go to a hydraulic clutch. I think I have that figured out. I'm hoping to get the clutch/brake pedal assembly from the donor vehicle. My question is what parts should I buy new? Slave cylinder I would buy new so as not to pull the tranny out in the future to replace it. But what about the clutch master cylinder, clutch, throw out bearing?
3) I understand the zf5 for small block comes in wide and close ratio. How do I tell the difference? I believe I want the close ratio because I don't do much towing other than a small trailer and lawn mower.
4) I haven't figured out the drive shaft yet. Would that come from the donor truck as well?

Any thoughts on the swap or any answers to any of my questions would be much appreciated.

My 14 year old says he's going to drive this truck to high school so I want something he can drive easily and safely. There are a few other things I want to do to the truck but this is the starting point. And I have some time before he starts driving.

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01-31-2014, 04:29 PM

GaMachinist

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I'm interested too in this swap so I'll be following. My main difference is mine is 4wd.

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01-31-2014, 05:13 PM

blue04.5

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Slave cylinder attaches to the outside of the transmission case I thought?
Driveshaft will probably have to be custom I would guess.
Good luck with your quest/project. Have any pictures of your truck?

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01-31-2014, 06:25 PM

tndallas

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According to my research the small block (302 351 v6 etc) zf5 slave cylinder is internal while the big block is external. I have seen info where someone using the big block used mechanical linkage to connect to the external clutch fork and by passed the hydraulics. No such luck on the small block.

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01-31-2014, 06:58 PM

whc8100

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Small block ZF is wide ratio only, still a tighter ratio than your T18. Slave is hydraulic and internal. Easy to rig up the hydraulic setup lots have done it on hear including myself. I think the harder part is the shifter as the tranny is taller and hard to make the shifter look "right" in the older truck. IMHO.

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01-31-2014, 07:35 PM

tndallas

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According to blue oval the s542 and s547 both have close and wide ratios. But I agree with you that it's better than the t18.

How does the zf5 drive. Do you pull out in 1st or 2nd? I had a 2001 v6 f150 w/Mazda tranny so I'm figuring its somewhere between the two.

Any tips on working on the shifter?

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01-31-2014, 08:07 PM

whc8100

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I take off in 2nd with 3.50 gears, 460 and 31" rubber, a lot like the four speed. The close ratio is only on the diesels. Still haven't figured out my shifter yet. Using the stock zf one and it works fine just looks out of place. Good thing with the small block ones is the input shaft is the same as the T18, no need for a new clutch.

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01-31-2014, 08:07 PM

Fordidipower

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Had two idi's with the close zf's and starting from a stop in 2nd wasn't a prob. But thats behind a diesel so not sure behind a gasser

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01-31-2014, 08:23 PM

GaMachinist

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My truck is still new to me, I can't start in 2nd with the NP435 behind the 300ci without it shuttering pretty bad. Was hoping the zf5 would alleviate that and have the 1st gear for towing.

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01-31-2014, 10:01 PM

fitzmotor

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I did the swap and it ended up being like a 4 speed, I never used 1st unless I was crawling in 4x4, but it was a great upgrade, used mechanical clutch linkage.
Note; a 2 wheel drive 5 ton box truck trans fits in a 4x4, take off the trans mounted parking brake and you have a transfer case flange.

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01-31-2014, 11:13 PM

blue04.5

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The only zf5 I've been around was behind my 95 powerstroke and it had the external slave. Had 3.50 gears and 35inch tires and started in 2nd. Its an OD transmission so you will still have better cruise rpms than the t18 right for the OP?

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01-31-2014, 11:25 PM

GaMachinist

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Quote:

Originally Posted by fitzmotor

What year range will fit from the box trucks will fit? I thought they had big blocks in them.

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02-01-2014, 09:03 AM

loudfords

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Quote:

Originally Posted by tndallas

2) I know I will have to go to a hydraulic clutch. I think I have that figured out. I'm hoping to get the clutch/brake pedal assembly from the donor vehicle. My question is what parts should I buy new? Slave cylinder I would buy new so as not to pull the tranny out in the future to replace it. But what about the clutch master cylinder, clutch, throw out bearing?

4) I haven't figured out the drive shaft yet. Would that come from the donor truck as well?

Slave cylinders from several different years will work, but make sure to get master & slave cyls as a matched set (ie. from same vehicle) is what I found out when I looked into this swap years ago.

Driveshaft needs to be 2 piece, as ZF has fixed rear yoke on it, not sure what the T18 has. You will also need to make a new tranny crossmember. The tranny is shorter than a C6 (dunno about T18) but the mount is farther to the rear.

Some time ago I had saved a link to pictures from someone who converted the stock clutch linkage to run the hydraulic clutch, but no idea if I could find this back.

I never got around to installing my ZF, and now the truck is parked in the garage indefinitely waiting for restoration.

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02-01-2014, 09:10 AM

fitzmotor

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It was a big block, I thought I would stick that in as useful information, I searched for a BB gas engine 4x4 ZF for a quite a while until I found a cross reference to a commercial application, then a trans was easy to find, sorry I should have mentioned the BB application.
Oops that was kinda a hijack on my part.

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02-01-2014, 09:26 AM

tndallas

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Quote:

Originally Posted by loudfords

Driveshaft needs to be 2 piece, as ZF has fixed rear yoke on it, not sure what the T18 has. You will also need to make a new tranny crossmember. The tranny is shorter than a C6 (dunno about T18) but the mount is farther to the rear.

The T18 is 2 pieces as well. I think my dad had a machine shop customize the driveshaft to make it work. I hope I don't have to do that. I know he had a problem getting it balanced. Is the output yoke the same on the T18 as the ZF? I understand from several comments here to just move the cross member back and drill new holes and it will work w/ the ZF.

Quote:

Originally Posted by loudfords

Some time ago I had saved a link to pictures from someone who converted the stock clutch linkage to run the hydraulic clutch, but no idea if I could find this back.

I found this info on this forum:
 "Clutch pedal assembly from 87-91F-series (150, 250 or 350 makes no difference)
The small arm from 80-90s clutch pedal that connects to the master then “cut and weld” - Link
Clutch Master cylinder line - I'd suggest running these Clutch adapterwith a braided -3 AN line.
Get a 1991 or newer ZF5 because it will have the mechanical speedometer in the transmission as the older ZFs don't have the speedo--I think they used the speedo on the axle????"
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I haven't found a lot of details about how to drill the hole in the firewall. But I figured when I get the clucth/brake pedal I can figure out something. Hopefully I can drill the hole in the correct location the first time. I know it is close to the brake booster on the engine side of the firewall.

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