Transmission swap
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Junior User
Joined: Apr 2010
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From: Trinity NC
Transmission swap
I have a 85 carb 300 with a 4 spd with od 4x4. it is geared too high so im thinkin im gonna swap it out for a 5 spd out of a later model efi 300 4x4 will it bolt up? and is this a good idea?
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Joined: Dec 2007
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From: Boise, Idaho
It'll depend on the transmission you get. If it's the Mazda 5 speed, it'll have the same gearing as the one you currently have, just spread out to 5 gears instead of 4. If you get the ZF-5 speed, it'll be the same transmission you currently have, except it'll have an additional granny gear.
Either way, neither will really change your overall performance unless your only issue is off the line (in which the ZF will help.)
The biggest factor you'll run in to is whether or not you currently have a hydraulic or mechanical clutch. If you have a mechanical, you'll have to convert it over to a hydraulic setup to use either of the trannies. Other than that, they're pretty direct swaps with minor issues like crossmember location and driveshaft length.
All in all though, if gearing is your issue, you may just be better off regearing. If you have a 3.08 final, go with a 3.55. If you have 3.55, go with a 3.73, 4.11, etc.
Either way, neither will really change your overall performance unless your only issue is off the line (in which the ZF will help.)
The biggest factor you'll run in to is whether or not you currently have a hydraulic or mechanical clutch. If you have a mechanical, you'll have to convert it over to a hydraulic setup to use either of the trannies. Other than that, they're pretty direct swaps with minor issues like crossmember location and driveshaft length.
All in all though, if gearing is your issue, you may just be better off regearing. If you have a 3.08 final, go with a 3.55. If you have 3.55, go with a 3.73, 4.11, etc.
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Joined: Apr 2004
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It'll depend on the transmission you get. If it's the Mazda 5 speed, it'll have the same gearing as the one you currently have, just spread out to 5 gears instead of 4. If you get the ZF-5 speed, it'll be the same transmission you currently have, except it'll have an additional granny gear.
Either way, neither will really change your overall performance unless your only issue is off the line (in which the ZF will help.)
The biggest factor you'll run in to is whether or not you currently have a hydraulic or mechanical clutch. If you have a mechanical, you'll have to convert it over to a hydraulic setup to use either of the trannies. Other than that, they're pretty direct swaps with minor issues like crossmember location and driveshaft length.
All in all though, if gearing is your issue, you may just be better off regearing. If you have a 3.08 final, go with a 3.55. If you have 3.55, go with a 3.73, 4.11, etc.
Either way, neither will really change your overall performance unless your only issue is off the line (in which the ZF will help.)
The biggest factor you'll run in to is whether or not you currently have a hydraulic or mechanical clutch. If you have a mechanical, you'll have to convert it over to a hydraulic setup to use either of the trannies. Other than that, they're pretty direct swaps with minor issues like crossmember location and driveshaft length.
All in all though, if gearing is your issue, you may just be better off regearing. If you have a 3.08 final, go with a 3.55. If you have 3.55, go with a 3.73, 4.11, etc.
The 4OD: 3.25/1.92/1/.78
The Mazda: 3.91/2.24/1.49/1/.80
The ZF: 5.72/2.94/1.61/1/.76
Mostly road, no heavy towing or loads? Mazda. Will still be ok off road due to low range in the tc if needed. 3.91 is a bit better than 3.25, and you get rid of the god-awful 2nd to 3rd gap in the 4 speed OD.
Heavier loads, towing, lots off road? ZF. Still fine on the hwy, now you have a real creeper gear, and you still reduce the 2-3 gap.
My '85 had a juice clutch with the 4 speed OD. Not sure how that set up will match up with the ZF or Mazda set up, but it will be closer than a mechanical set up!
IMO, the gearing idea is sound, but the 4 speed OD will still have the gap issue and a tallish first. Heck, do both.
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Junior User
Joined: Apr 2010
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From: Trinity NC
Mine has a hydralic clutch and i dont think the tranny i found is a mazda. Where i need the low gear is off the line pulling. first gear in my current 4 spd is just too tall. its about right when im not hauling or pulling but when i am it just dont work. is there an easy way to tell the mazda from the zf?
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Joined: Dec 2007
Posts: 7,987
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From: Boise, Idaho
If your issue is mainly off the line with heavy loads, the ZF will do you great, that and it's a bit more heavy duty than the Mazda.
There should be some identifying numbers on the casing, but from what I hear, the ZF actually has a "ZF" cast onto the side of it.
Elder User
Joined: Nov 2006
Posts: 973
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From: Texas
Go with the ZF. I swapped a ZF in place of my mazda. The mazda has too many problems and is a much lighter duty transmission. And you will be thankful for the lower first gear in the ZF, it isn't quite a granny, but its close.
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Joined: Apr 2004
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'87-'88 for these transmissions to go to integrated bell. Pics here:
Domestic Truck Tranny Guide
You'll see the difference between to two--big enough diff to spot from a distance. Look for the ZF in F250 and above vehicles with the 300 or 351W.
Domestic Truck Tranny Guide
You'll see the difference between to two--big enough diff to spot from a distance. Look for the ZF in F250 and above vehicles with the 300 or 351W.
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From: Gadsden Purchase
Postmaster
Joined: Aug 2005
Posts: 2,760
Likes: 8
From: Gadsden Purchase
Butthead in AZ
NP435 = 6.69 3.34 1.74 1.00 r8.26
T18 === 6.32 3.09 1.69 1.00 r7.44
4OD=== 3.25 1.92 1.00 0.78 r=?? (from "83's" post)
Mazda = 3.91 2.24 1.49 1.00 0.80 r3.39
ZF ==== 5.72 2.94 1.61 1.00 0.76 r5.72