5-speed swap?
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New User
Joined: Sep 2010
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From: Troy, MO
5-speed swap?
I just got an 87 bronco with the 300 inline 6 and a four speed. its only got 115,000 miles and barely any rust (just the rear fenders and a bubble on the tailgate). My problem is- I love the 4-speed, but its high geared. It's great for highway driving and cruising, but would be a nightmare for trails and backing trailers. you have to ride the clutch a lot on hills also. Would a 5-speed have a lower first gear and reverse? would it be worth my time to swap one in?
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Joined: Apr 2004
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ZF 5er has a lower first, and less of a gap than that 4 speed. You probably have the 4 speed OD, with a tall first, a big gap 2nd to 3rd, right?
The ZF will be found behind 300s and 351ws in F250 and larger trucks. It is an integral bell, internal slave throwout bearing set up.
You should have a hydraulic clutch already.
Info here:
Domestic Truck Tranny Guide
Note there is also a Mazda built 5er found behind 300s and 302s in F150s. First is not as low as the ZF, but at 3.91, lower than the 4 speed. Ratios are tighter too. Not sure about reverse, may be a little high.
Ford Motor Company Transmission Gear Ratio's
The ZF will be found behind 300s and 351ws in F250 and larger trucks. It is an integral bell, internal slave throwout bearing set up.
You should have a hydraulic clutch already.
Info here:
Domestic Truck Tranny Guide
Note there is also a Mazda built 5er found behind 300s and 302s in F150s. First is not as low as the ZF, but at 3.91, lower than the 4 speed. Ratios are tighter too. Not sure about reverse, may be a little high.
Ford Motor Company Transmission Gear Ratio's
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New User
Joined: Sep 2010
Posts: 13
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From: Troy, MO
Thanks for the help. I'm probably going to look for the 3/4 ton ZF, but I'll wait until I burn up the clutch in the 4-speed before I do the swap 
I have to drop some money on tires first, they didn't work so well on this foot of snow we got here in Missouri. lol
I have to drop some money on tires first, they didn't work so well on this foot of snow we got here in Missouri. lol
Lead Driver
Joined: Sep 2002
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From: Gateway to the West
Recently did some number crunching based on the setup you are considering. This thread details my math and the suggestions of from several others. BTW the overall crawl ratio of a wide ratio ZF, BW1356 t-case, and 4.11:1 axle gears is better than 60:1 in first with the t-case in LOW.
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Joined: Mar 2005
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From: Earth
To do the ZF swap you'll also need the tranny crossmember from the donor truck and you'll need to shorten the rear and lengthen the front driveshafts. The transfer case shifter is a pain, but later model trucks may have the cut-out in the floor already?
The ZF drives like a three speed around town - hardly ever use the granny 1st (5.72:1 iirc) and the OD is only for highway speeds. It's got a pretty low 2nd gear, too; easy to start off in 2nd. No worries, great swap. My Bronco came with a T-18, so I basically just picked up an OD gear and synchronized 1st.
The ZF drives like a three speed around town - hardly ever use the granny 1st (5.72:1 iirc) and the OD is only for highway speeds. It's got a pretty low 2nd gear, too; easy to start off in 2nd. No worries, great swap. My Bronco came with a T-18, so I basically just picked up an OD gear and synchronized 1st.
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