Jatco 3 speed

[mikecaleb]

I've got an 86 720 with a z24 and 3 speed auto. Bought the truck needing some carb work. Swapped it for a weber 32/36 I had laying around. Got it running and drove it around for almost 2 weeks when one night while driving it the Trans started making an awful noise when coming to a stop. About 2 stop signs later the truck would.no longer go into gear. Truck still starts up and runs no problem but won't go into any gear. What could this be? Linkage is intact, vacuum line appears to be fine. And I've got the pan off right now. Was going to change filter and try to adjust bands. Anyone know the correct procedure to do so? Thanks in advance 

 

 

[mikecaleb]

Would like to keep the auto. But if it comes down to it I have a 86 hardbody with a 5 speed sitting in it that I can use. If I measured correctly they are both 31.5.  Am I wasting my time attempting to save the auto? 

[datzenmike]

What does the fluid look like? color? smell burnt?

 

Did you recently check the level or top it up?

[mikecaleb]

Definitely not bright red. But no didn't change it or top it up. Don't recall checking it though. It's been some months that the truck been parked

[mikecaleb]

Also yes it did smell a little burnt. Also the filter seemed to be clogged. I never saw any fluid actually come through the filter part when taking the bolts loose. Only out of the bolt holes of the filter

[datzenmike]

Replace filter and change the DEXRON AFT. Nothing to loose. The old GM S10 Blazers and the Ford Bronco II s would whine when cold from unchanged filters. This was caused by cavitation.

[mikecaleb]

Alright. So I don't need to adjust the band before putting cover back on 

[datzenmike]

The brake band servo is on the driver's side front corner, round about the size of a soup can with three retaining bolts and a stem sticking down in the middle. The brake band stem has a lock nut, loosen it out of the way and tighten the stem to 9-11 ft lbs. Loosen 2 turns and secure the lock nut 11-29 ft lbs.

[mikecaleb]

Thank you will try that in the morning 

 

[mikecaleb]

Well I ended up breaking off one of the pan bolts. Now it won't hold fluid. I think I'm ready to call it quits on trying to save the automatic. 

 

[mikecaleb]

What would be the best approach to getting this truck back on the road? 

 

[NC85ST]

You’ve got 3 options: fix the broken bolt, find another transmission (might be difficult) or replace it with a 5-speed. You said you have a hardbody with a 5-speed, if it’s the same body type as the 720, both king cab or regular cab, you should be able to swap everything in, including the driveshaft. The only thing I’m not sure would cross over is the pedals. Depends on how bad you want an automatic.

[mikecaleb]

I'd rather have the 5 speed. Only reason I was interested in keeping the auto was because I've read that they are sought after in some places. I've measured the Trans and they both seem to be 31.5 inches long. And awhile back I fount the pedal assembly on ebay. Maybe it's still up for sale 

[mikecaleb]

It looks like switching yokes will give me the correct length drive shaft. Or am I overlooking something? Left if 86 king cab nissan 720 2wd auto, right is 86 hardbody regular cab 2wd manual (the vehicle that the 5 speed came out of). 5 speed bolted right up to stock crossmember location along with Trans mount. 

[datzenmike]

'86.5 was the end of the 720 and the beginning of the Hardbody. The Hardbody used the new 71C 5 speed and they are different length than the older 71B. If you have a Hardbody 5 speed, changing the Hardbody driveshaft with it might work.

 

The Hardbody 5 speed has this shift mechanism? 6 bolt cover with round hole for shifter?

 

 

 

[Stoffregen Motorsports]

Swap it. Autos are horsepower suckers.

[iceman510]

I think I have the short driveshaft section from an '81 720 2wd 5 speed around here if you need something for parts. I also still have the 5 speed trans, starter and the flywheel.  Might make for bolt in situation.

[mikecaleb]

Where are you located ice man? And I beat the yoke off the auto driveshaft last night. Starting to wonder if it'd be worth it to just go get the driveshaft shortened. The 5 speed drive shaft is bigger in diameter. And has a new center support bearing. 

 

It seems to be only the yoke on the auto drive shaft that's not allowing it to fit. Being it won't slide in tail of the trans.

 

[NC85ST]

If you can find a driveshaft from a king cab hardbody, it would probably be the easiest, unless you have a good driveshaft shop close to you.