73 4 speed to 81 5 speed transmission

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04-11-2004, 04:52 PM

bluesman1958

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73 4 speed to 81 5 speed transmission

I just purchased a 81 5 speed trans for my 73 240. I was told by the seller that it will bolt right up. Is this true? The shifter looks like its shorter with a crook to the left and I was wondering if it's going to work. Has anyone out there in forum land attempted this swap?
alan

04-12-2004, 07:45 PM

bluesman1958

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This transmission

The transmission is marked on the top with one of those paint pens "81 280ZX". Is this a T5? Does anyone know what the gear ratios are? In swapping it with my stock 4 speed in my 73 240, can anyone share the pros and cons? More bottom end? Better gas milage? ????
alan

04-13-2004, 12:07 PM

Bleach

The Evil Twin

Join Date: Mar 2001

Location: Seattle, WA

Posts: 9,294

It will bolt up fine. I think even the length is the same as the 240Z 4-speed so the rear mount will line up. I'm not totally sure on that.

The T-5 is all aluminum housing and was only available in the 1982-83 turbo. The 81 turbo came with automatic only. However, if it is a T-5 then it may have been swapped into a 1981 car.

If it is indeed a non-turbo 1981 transmission it will have more top end speed. A lot more. That transmission has a higher 1st, 2nd, and 3rd gear than your 240Z's transmission so if you leave the rear gear the same you will have less torque. 5th gear is very tall and you'll be at a very low rpm at highway speeds. The 81 280ZX came with a 3.9:1 rear gear ratio. I think your 240Z has a 3.3:1 or maybe 3.54:1 For best results, swap to a 3.9 or 4.11 rear differntial.

1st: 3.062
2nd: 1.858
3rd: 1.308
4th : 1.000
5th: 0.745

04-15-2004, 08:01 AM

bluesman1958

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Thanks for the reply

Makes me wonder if I want to swap or not. I would like to have the stop light to stop light torque. Does this mean I'm going to loose this in the swap if I don't change the rear gearing? I would like to have the best of both worlds. I'm installing a stage III cam, triple 40mm carbs, header with 2 1/2" exhaust.
What would you do?
Thanks,
alan

04-15-2004, 08:20 AM

AllmyZs

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If you want the best of both worlds, get a 5 speed out of a 75-78 280Z, or get a tranny out of a 77 Datsun pickup. You will have to swap out the bell housing, but this was the best combination i ever had. I did this to a 70 240Z, off the line was great up to 4th was nice and powerful. 5th was for the highway only. i could cruise at 85 doing just over 3k rpm. When i finally blow my tranny out of my 78 280z i am doing this swap.

04-15-2004, 03:31 PM

zr8d

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Join Date: Oct 2003

Location: boise, id

Posts: 123

i have a different point of view on that but mine is not from experience it's from what i've read and learned by talking to old z guys out here. The T-5 is really the way to go from what I here because the 5-speed that came in the 280z's was a four speed transmission that was forced into a 5-speed by adding the 5th gear to the same tree as 4th which makes it very weak. So, it has a tendency to wear out quicker. You'll still get a lot better performance out of a 5-speed over your stock tranny even without doing the rear diff upgrade. It would be a huge improvement if you were to do it though.