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Index > Engine/Drivetrain > Thread: Driveshaft -> Differential bolt size
Thread: Driveshaft -> Differential bolt size
rotarynews


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Too Many Rotary Websites
Posts: 206
posted September 29, 2001 07:02 PM

Driveshaft -> Differential bolt size


Anyone know the bolt size that holds the driveshaft to the differential? Metric size 8 (m8) is too small, and it looks like M10 is too big, or maybe the wrong thread size.

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Jeff20B


Moderator
Posts: 661
posted September 30, 2001 12:41 AM

Try an SAE like a 1/2 or 9/16 or 3/8 or whatever those things are haha (I like metric). Chances are somebody replaced the stock Mazda bolts with some easily obtained off-the-shelf, cheap bolts and nuts. Unless they thread into the diff part? It's been a few years since my tranny swap so I can't remember if it used nuts and bolts or just bolts. It's also late at night here so I can't go out and check.

By the way, I think I used 12mm or 14mm tools on mine. Only one of mine was tight. The rest were finger tight! However the one that was tight was extremely hard to remove. I think it was over torqued or something. While reinstalling everything, I used blue loctite. You should have seen what a loose tranny mount bolt will do to aluminum (especialy when the other bolt was missing).

Did the above paragraphs make any sense? Sorry, but I really tired (yawn).
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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rotarynews


Moderator
Too Many Rotary Websites
Posts: 206
posted September 30, 2001 01:57 PM

Yep, threads into diff yoke

quote:
Unless they thread into the diff part?


Yep.. this is the case...

What I ended up doing is got a set of M8 bolts that were just long enough, some washers and lock washers, and pulled the whole thing together.

I still don't have a clue what thread size it is going into the diff.. M10 didn't work, nor did the near-same size English bolt work...

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Jeff20B


Moderator
Posts: 661
posted September 30, 2001 11:28 PM

Ah, that's what you meant. I was too tired to notice that you were describing thread pitch! Oh man! Hmm, is it the same as the pressure plate to flywheel bolts? They are m24 I think. The battery box negative ground bolt is different however. It has a strange pitch (I should know since I once tried to find a replacement).

Good luck and let me know how it turns out.
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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draggin_2600i


Redlining
Posts: 235
posted May 21, 2002 08:09 PM

How can I check to see which differential I have on my 75 REPU. Does it matter if it was automatic or standard? I don't know what tranny the truck had since the whole setup had been swapped out before we bought it.

       
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jfaplanet


Redlining
Posts: 356
posted May 21, 2002 08:16 PM

What it should be

If its a 75 with a 4 speed it should be a 4.375, with an automatic it would have been a 4.111. 76 they went to 4.111 in both and 77 was a 3.900. This information was taken from http://mrmazda.members.atlantic.net/tranchrt.txt if you want to see some other numbers.


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draggin_2600i


Redlining
Posts: 235
posted May 21, 2002 08:55 PM

thanx for the link. The problem I have though is that I have no Idea if the truck was automatic or not. The whole engine and tranny had been swapped out for a 4 cyl. engine and 626 tranny. is there a way to check on the diff. itself?

       
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Jeff20B


Moderator
Posts: 661
posted May 21, 2002 11:37 PM

Is there a clutch pedal? Even that won't be 100% proof, but it's a start. Next, check the door plaque (that sheet metal thing that shows the GVWR and stuff). What does it say?

       
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Brad


Rotorhead
Posts: 1671
posted September 17, 2002 02:34 PM

to determine what ratio your diff has:

jack up the rear of the car so the tires are off the ground
take off brake and put it in neutral
spin the driveshaft by hand
how many turns of the driveshaft it takes for the tires to make one full rotation is what your diff's ratio is

so if the driveshaft has to be turned 4.62 revolutions for the tires to make one revolution, u got a 4.62.

u get the idea

--- it might be easier to spin the tire than the driveshaft!


____________
-brad-
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-
Bridge

       
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repuguru


Redlining
Posts: 319
posted September 17, 2002 08:23 PM

I think that the tunnels were cut with different holes? The manual with a large round one for the tranny tower. The auto had an opening that was not quite as large with a braket to bolt the shifter to.
If someone put a piston combo in they obviously gave no reqards as to modify the tunnel or not, so it still may be tough to tell.
There were relays that would have been in the cab itself and not on the original auto drivetrain when it was pulled.
Most REPU's had a stick...SO who knows?????

       
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Brad


Rotorhead
Posts: 1671
posted March 26, 2007 08:34 AM

back from the dead

quote:

Anyone know the bolt size that holds the driveshaft to the differential? Metric size 8 (m8) is too small, and it looks like M10 is too big, or maybe the wrong thread size.



It's M10 x 1.25mm. An oddball thread, most M10 are x1.50mm.

And the nuts that hold the driveshaft center bearing to frame are same thread, as are nuts&bolts that hold rear axle bearing housing to axle housing itself in case anyone's keeping score.

I just bought and installed zinc plated nylox nuts for the above two items from thenuttycompany.com.
____________
-brad-
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-
Bridge

       
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