d21 SD25 Transmissions?

SD diesels were widely available in the US in the 1981-86 Datsun/Nissan 720 pickups, and in Canada through '87 in the D21 pickup.

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niseamer
Posts:19
Joined:7 years ago
Location:Ucluelet, B.C. Canada
d21 SD25 Transmissions?

#1

Post by niseamer » 7 years ago

Hi Folks

I have an D21 with an SD25 in it. 2wd with a 5 speed manual tranny. I have a spare motor as well.
I had the transmission rebuilt last year in Port Alberni B.C. and it just jammed in 3rd gear. I managed to get home in third, but only just squeaked over a couple of the mountain hills. When I got home and checked the oil there was NONE!

I am not sure I want to spend another $1000 (or more) on yet another rebuild so am wondering if anyone knows of another transmission that would go in there without redesigning the truck. Would one work from another year and from a gas engine model? I'm not too worried about gear ratios, though I do like what I have now. The big thing is whether it is the right length and/or can mount to the bell-housing.
Nissan dealers tell me that it is specific to that vehicle, but they often don't know much about these vehicle and are only going by what the book says "is recommended" for it.

Perhaps there is a Toyota or other make that would be useable?

Thanks

Niseamer
I live in Ucluelet, B.C. Canada (west coast of Vancouver Island)

dn29626
Posts:249
Joined:10 years ago
Location:Anderson, SC

#2

Post by dn29626 » 7 years ago

The front section of the five speed transmission (diesel and gas) will interchange between a gasser trans and a diesel trans.
Do not damage that front section of the diesel trans. It is the hard-to-find part.
82 King Cab 2wd (nice)
82 Reg Cab (body damage)
Anderson , SC
Since Fall 2009

niseamer
Posts:19
Joined:7 years ago
Location:Ucluelet, B.C. Canada

d21 5 speed transmission swap

#3

Post by niseamer » 7 years ago

dn29626 wrote:The front section of the five speed transmission (diesel and gas) will interchange between a gasser trans and a diesel trans.
Do not damage that front section of the diesel trans. It is the hard-to-find part.
Thank you so much.
This makes my decision a lot easier! I got the tranny sitting on the ground today...I can see it will be a lot harder to align everything for the install though..it seems to be a tight fit for a backyard mechanic with minimal jacks etc.

I will treat the front part of the case like fine china!

Cheers

Gerry

dn29626
Posts:249
Joined:10 years ago
Location:Anderson, SC

#4

Post by dn29626 » 7 years ago

82 King Cab 2wd (nice)
82 Reg Cab (body damage)
Anderson , SC
Since Fall 2009

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asavage
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#5

Post by asavage » 7 years ago

There's also my Dec2005 write-up, which is not as good as the article linked above.

It's here.
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.

niseamer
Posts:19
Joined:7 years ago
Location:Ucluelet, B.C. Canada

Re: d21 SD25 Transmissions?

#6

Post by niseamer » 6 years ago

niseamer wrote:Hi Folks

I have an D21 with an SD25 in it. 2wd with a 5 speed manual tranny. I have a spare motor as well.
.....
...... wondering if anyone knows of another transmission that would go in there without redesigning the truck. Would one work from another year and from a gas engine model? I'm not too worried about gear ratios, though I do like what I have now. The big thing is whether it is the right length and/or can mount to the bell-housing.
Nissan dealers tell me that it is specific to that vehicle, but they often don't know much about these vehicle and are only going by what the book says "is recommended" for it.

Perhaps there is a Toyota or other make that would be useable?

Thanks

Niseamer
In case anyone is interested:

I got another transmission (FS5W71C) from a 1995 Nissan gas pick-up.
I switched the bell housing from my truck. Put it all together and tested yesterday.
I was told the transmission would have to come from something before 1993, but this one works fine.
Everything fit in perfectly and the transmission works well. I was unlucky enough to get one with a little higher gear ratios in the lower end, which means a higher 1st, 2nd and 3rd gear are higher. I am not sure that 4th and 5th are higher though....I don't have a tach.
I would like to have a lower 1st and second though....such is life.

I also put in a different SD25 since the other one was getting little tired with over 500,000 km on it (though is still ran fine). This one has an in-line pump rather than the rotary on the original. I does have a bit more power and does get better mileage. One three hour run got me 43 mpg (imperial), though I am skeptical about my math on that!..seems pretty high except that I did get up to 39 mpg on my older engine once. The older one averaged about 33 mpg, whether running on veggie oil or diesel.

After a bit of testing I will be adding my old veggie oil system to this one as well.

So far I am happy with both the transmission swap and the engine....

Hope this info is helpful to someone pondering this swap as well. Open to questions etc......

Thanks to everyone for their help on this.

Cheers
Niseamer

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