Transmission grinding into 2nd and popping out of gear

[Rshields85]

1986 Nissan 720, 2wd shortbed, 5 speed. Door plate says FS5W71B, but I am only finding rebuild kits for the 71C. Transmission is leaking from rear output shaft, grinds into 2nd gear, and will pop out of gear when I let off the gas. 5th gear also has a strange rattle, but doesn't grind into gear. Also occasionally if I let it sit and warm up the engine will stall out when I let out the clutch, but as soon as I put it back in it will idle fine. If I just start it up and go I do not encounter this problem. Also I can't shift into first gear unless I am completely stopped. Once stopped, shifts in just fine.

 

So what I need to know is will the rebuild kits offered online from companies like cobra transmission that advertise their kit as being a direct fit for my truck work even though they are listed as being for a 71C?

[G-Duax]

I found my 71B kit on eBay.

[datzenmike]

The trans is likely pooched but probably caused by a dragging clutch.

 

Place in neutral, let out clutch. Now depress clutch pedal and slowly try to place into reverse. Does it grind gears?

[Rshields85]

Just did your test datzenmike, no grinding.

[datzenmike]

There's not much you can see or do from the outside. One thing is check the transmission oil level. The fill plug is about half way up the driver's side. You should easily be able to dip your finger into the oil if it is full. Might be a good idea to just change it if you have no idea when it was changed last. Two liters of GL-4 80w90. Do NOT use GL-5 as it contains concentrated additives that will attack your brass synchro rings. Any oil you use must be GL-4 or marked safe for brass/copper/'yellow metal'. This is unlikely to fix the problem if the transmission is full but if low or near empty.... you never know.

 

Is the end of the tailshaft where the driveshaft connects, wet with oil? This would indicate the transmission is low or perhaps empty.

[Rshields85]

It is leaking there and the fluid appears to have metallic particles in it. I'm going to het some GL4 today per your recommendation and drain and refill it. If it is wet back there though wouldn't that indicate a leaking output shaft seal?

[datzenmike]

Yes it does. If leaking, how long? Long enough to run dry? Long enough to grind up the bearings? Re-filling may prolong the use of it but any damage done is permanent.

[Rshields85]

Fairly recent, and very little. I intend to rebuild it for piece of mind, but I am hesitant to buy a kit labeled for a 71C, are there any rebuild kits out there that you recommend?

[datzenmike]

The switch to the 71C from the 71B was '86.5. The C signifies the style of shift mechanism. However some other C transmission parts were also introduced on late 71B transmissions. The after market transmission rebuild kits don't include the shifter so as long as the bearings and synchros are compatible they called them a C even if in the older style B case.  Only way to be sure and get the correct B parts is from Nissan. Otherwise quote your exact year/model and build date when ordering parts.

[Rshields85]

Build date is 12/85 so I am assuming it does have the 61mm countershaft bearings along with the other upgrades to 71C standards. Would mine have the syncros that are all the same size?

[datzenmike]

1-4 are the same but 5th is not. The C type are different again.

 

All 720 after Sept '84 have the 62mm counter bearing 32219 V5201

[Rshields85]

Do you happen to have the p/n for the syncros I would need as well, from what I am seeing piecing together my own transmission rebuild kit from nissanpartdeals.com may not be the cheapest, but best, option to ensure correct fit and longevity.

[datzenmike]

Build date is 12/85 so I am assuming it does have the 61mm countershaft bearings along with the other upgrades to 71C standards. Would mine have the syncros that are all the same size?

 

1-4 synchros.............. 32604-P0100 about $40 ea

5th synchro................ 32604-E9801 about $50