Datsun Roadster Forum-311s.org

Can anybody tell me the physical difference between a 4 speed and 5 speed transmission mount. I'm currently using a 4 speed mount on my 5 speed transmission. Third gear wants to slip back to neutral if I don't hold it in. I'm wondering if swapping to the 5 speed mount will change anything. Will it change the driveshaft angle for example.

Do you mean the crossmember or the rubber mounting?

Guess I should have included the cross member in the post. Pretty sure both are for the 4 speed. I assume I probably need to swap both pieces??? The drive-line angle does look kind of steep but I don't have anything to compare it to.

Yes, you need the 5 speed crossmember. I think that you can make the mounts work (different bolt sizes iirc, but I am not sure of the detail differences), but the crossmembers are wildly different.

Big differences, there are at least 3 different mounts check here for lots of details and measurements: http://www.311s.org/phpBB3/viewtopic.ph ... t&start=30
Now, do you have to hold it in gear because the shift lever is physically hitting the transmission hump hole? If so, then yes the mount may fix it, but if it is not physically hitting something, and pops out of gear, I would think something mechanical inside the box is at fault. With my experience, I am surprised you can even get a 4 speed mount to work - it just wouldn't physically bolt up for me, I couldn't get the engine mounts to line up.

Thanks for the links to reference guys. I'm going to crawl under tomorrow and have a closer look. I'll post some pics afterwards.

rubber mounts are interchangeable as the only difference is the hole size on the 5 speed is slightly larger. the big difference in the steel mounts is that the 4 speed mount is much taller than the low profile 5 speed steel mount. Did you use the thicker 5 speed plate between bell housing and transmission case?

Ross
sports imports

Unfortunately I bought the car in boxes so I don't know exactly what I have. I did notice today that it looks like the front of the tunnel is what's causing the transmission to slip from 3rd into neutral. Does the fact that the shift lever sits so far forward tell you anything about changes I need to make?

Pictures would help, but yes, it sounds like the mount might be incorrect. Look at the front motor mounts, are they stressed/stretched at a front to rear angle?

Are you CERTAIN that the car had a 5-speed INSTALLED.
The lengths of the transmissions are different inasmuch as the gear shift lever position is concerned.

Pix would certainly help.

I've taken these pictures, but I'm not sure how much they'll actually tell you. The flange the shift lever goes into is 1 1/2" from the front of it to the front of the tunnel. From the back of the flange it is 4 1/2" to the rear of the tunnel cut out. Seems to me the lever should be further rearward as the shift now is nearly under the dash in 1st, 3rd and 5th gear. Still trying to determine what I need to change. I included a shot showing the spacer between the gear box and the belt housing, not knowing if it should be a thicker version. The engine mounts are not stretched in any direction. I can measure the transmission mount if that might help determine what I need to do next. Another hint is that the gap between the U- joint flange and the front of the driveshaft is about 1 1/4 inches, with about 3/4" of splines showing. Any more thoughts?

What year vehicle, or frame? Earlier cars had different way of supporting the trans mount, and, yes, the mount height is different between 4 and 5 speeds.

Not seeing a pic where the trans bellhousing bolts to the engine.

Not recognizing what the middle row of pics are. Luckily, there's more knowledgable folks who can.

Are the bottom pics the trans drain plug? If so, then that's looks like a roadster 5-speed.

The car is a 67 1/2. The car originally had a 4 speed in it but I swapped it for the 5 speed. The middle row pics show the cross member and where the mount bolts up. Pretty much impossible to get a shot of the mount itself. The bottom row pics show the plate between the gear case and the bell housing. Does the lover appear to be coming out of the tunnel in the correct location?

When you put the 5 speed in, did you trim the tunnel sheet metal? On the 67.5, under the carpet, there is a stamping in the metal that you need to cut out to clearance the 5 speed lever. IF you can see clearly under the carpet you should be able to see the "indent" that needs to be removed.

The 67.5 tunnel does NOT need to be trimmed. It is big enough for both shifters to come up. Only the 68 and later have the detent. It has been a while since I have looked at it, but that appears to be a 4 speed crossmember. Replacing that will lower the back of the transmission, and it will also shift the engine and transmission rearward slightly. Dave Brisco modified a crossmember some time ago, but I don't recall the specs.

Of course I could be mistaken.