F.5 plus 4 spd

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Jul 29, 2007
Keene, Ca.
My F engine is coming out this week (burnt valve) to put in a '74 F.5 (transition engine; I really don't know what to call it). The guy I'm getting it from has also offered a 4 speed transmission and bell housing (I have a '67 with 3 spd). Will this basically bolt in or will I have to fabricate mounts and get new driveshafts, do I use a '74 clutch assembly etc etc? I will be keeping the original transfercase and buying the Mark's Offroad adapter to mate the 4 spd trans and TC. Any advice is appreciated.
I guess another question is: am I really gaining anything with the 4 spd? The 3 spd leaks a little and crunches from gear to gear but is still serviceable.
final drive ratio isthe same from 3 to 4 speed...you gain an extra gear while wheeling ...the advantage of the 4 speed.

f.5 .... or...... f and a half...f & 1/2 ...what ever you call it...i have one and they are a great motor...my last one lasted just shy of 430,000 miles...i replaced it because of all the oil leaks...and the lack of power...i put in a 60k f.5 ...and runs great.

i have the 3speed transfer to a 4 speed tranny...i dont remember putting in an adapter.

and afaik it bolts in ....but....i could be wrong...somebody else will chime in a bet :)
I think your motor mounts will be OK, but you will need driveshaft length adjusting.
I believe that is was late '74 that the change from the 3-finger clutch to the diaphragm happened...you could probably use either. As long as you use everything from either set-up.
congrats on a great motor...........seems the .5 F is the strongest of the series; my 0.02....go with the 4 speed!

You will also gain the lower 1st gear of the 4 sp and the lower 4 lo of the 3 sp t-case.

I'm finishing up a 4 sp tranny swap into my 71 with the 3 sp t-case. No adapter needed but you will have to get the following items:

29 tooth 16 spline t-case input gear (Mudrack has them or Mark A)
16 spline PTO gear or a spacer from a 4 speed t-case. (Mudrack or Mark A)
These gears are needed to mate the 3 sp t-case to the 16 spline 4 sp output shaft.

1974-1982 Datsun B210 pickup truck rear axle bearing part # RW114R (any good auto parts store) Needed to mate the 3 sp t-case to the 4 speed tranny output shaft.

Complete 4 sp tranny to t-case shift linkage if he doesn't have it. An option is to run the vacuum shifter stuff (what I'm doing). Then all you have to do is lengthen the 4-hi to 4-lo shifter linkage about 3 inches.

4 sp t-case to tranny bolts. (They are longer)

4 sp bell housing

Either the 3 sp or 4 sp clutch assembly will work but you must use all 3 sp or all 4 sp clutch parts, no mixing. I'm keeping the 3 sp clutch parts in mine to retain the heavier flywheel. The 4 sp clutch is smoother though...

An option on the drive shafts is to get a set of 4 sp shafts, a 4 sp e-brake drum, and a set of front and rear course spline pinion flanges and a front t-case output flange with the 4 sp hole pattern (from Cruiser outfitters). This will allow you to run STOCK 4 sp drive shafts which are stronger anyway and won't leave you on the trail with a custom drive shaft.


Be aware that the 4 sp tranny is longer resulting in the e-brake drum being VERY close to the cross member. So close in fact that you will NOT be able to pull the e-brake off (or drop the t-case) without either pulling the motor or removing the rear engine mounts and lowering the whole assembly.
Thanks for the advice. I'll start collecting the parts and seeing what I can scrounge up.

I appreciate the reply. I also looked at your website--what a wealth of knowledge.


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