Transmission troubles

Dealing with all subsystems specific to the diesel powered Datsun-Nissan 720 pickup trucks.

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greaseburner
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Location: southwest Manitoba, Canada

Transmission troubles

#1

Post by greaseburner » 12 years ago

Haven't had a chance to look at it yet, but this morning my tranny started to make a racket. Not a grinding noise. More like an out of balance shaft or something. And only in fifth. At first I thought maybe I was loosing 5th altogether, but that's not the case. All the other gears are fine. And fifth does work. It almost sounds like somethings hitting the driveshaft, but then it would be in all gears. I just did the clutch and pilot bearing about 8 months ago. BTW, I had some trouble before with slipping out of 5th if not under power. Any ideas??? I won't have achance to look at it until tomorrow, but suggestions can't hurt. Thanks :?:
1987 Kingcab SD25
Dave

Nissan_Ranger
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#2

Post by Nissan_Ranger » 12 years ago

Check your U-joints and hanger bearing CAREFULLY. Even a single seized U-joint cap can feel (and be ) quite tight and yet have the driveshaft out of true enough to cause a vibration that may show up only at higher speeds. Really loose joints are obvious; no further description needed :-)

Hope it works out...

N_R
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asavage
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#3

Post by asavage » 12 years ago

Nissan_Ranger wrote:Check your U-joints and hanger bearing CAREFULLY. Even a single seized U-joint cap can feel (and be ) quite tight and yet have the driveshaft out of true enough to cause a vibration that may show up only at higher speeds.
Not off-topic, really, because it's Nissan . . .

Early in my career, I did contract maintenance and one rig was a B210 with the A14 engine. It came in with a bad vibration. I swapped in a whole 'nother rear end, but the vibration persisted. It was a seized joint, and the first driveline I'd seen with non-replaceable joints. I put in a custom-built driveline with replaceable joints, problem solved.

The Nissan dealer had new driveshafts in stock!

greaseburner
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#4

Post by greaseburner » 12 years ago

It's definitely 5th gear. All the other gears are fine. No vibes there. I talked to a local nissan mechanic today while getting filters and hea said that the nut that holds the gear for 5th likely backed off. Not that uncommon apparently. SHould be able to pull the tail piece and snug it back up. Or so he said. The noise is much more akin to a gear that is not fully engaged and is skipping. Going to be bone for a couple weeks. I'll check it out when I get back. Thanks for the suggestions.
1987 Kingcab SD25
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#5

Post by davehoos » 12 years ago

main shaft bearings etc.
the [2]nuts holds the [2] fifth gears and the rear bearings.there is also a bearing after the nut that can be loose in the housing.
itis also not uncommon to break the lower shaft if you have been driving at low speeds it top gear.

if the front shaft has been strained by the clutch/pilot bearing you may need to replace all bearings.you havnt got symptom that indicate the front bearings are faulty.

with the rear housing off you should be able to check all.to do any serious replairs it all needs to come out.
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asavage
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#6

Post by asavage » 12 years ago

greaseburner wrote:. . . he said that the nut that holds the gear for 5th likely backed off. Not that uncommon apparently. SHould be able to pull the tail piece and snug it back up. Or so he said.
Member Knucklehead has a pic of the same problem over in the FS5W71x thread. Wordy, but highly recommended thread to read.

Image

If at all possible, you will want to replace at least the front bearings . . .
Image

. . . and even the rears go bad.

Image
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.

plenzen
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#7

Post by plenzen » 12 years ago

From reading this and the other threads that relate to the transmission woes on these little guys, am I to understand that it is "inevitable" that the transmission “WILL” die? Am I looking at a "hard" rebuild in my future? (all bearings, bushings, synchros etc.) I know that everything wears out, but are these like the early Chrysler Mini Vans or early 90's Ford Aerostar trannies and just pile up? Is there something that I can do to avert this, other than parking it?
Last edited by plenzen 12 years ago, edited 1 time in total.
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asavage
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#8

Post by asavage » 12 years ago

My bias is for synthetic lubricants, esp. for this transmission.. The early FS5W71 transmissions (pre 86) have too small of a front countershaft brg for the duty they get. That brg was enlarged for 1985.
Image

However, that's not the only brg that fails, and the reverse gear is fairly fragile (or Nissan owners are harder on them than usual, take your pick). OD gear's needle brg and the front/rear mainshaft needle brgs wear badly too. At the least, a better lubricant may delay the needle brg wear.
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.

plenzen
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#9

Post by plenzen » 12 years ago

I have bought the red line synthetic and will install same on the next oil change in about 800 Kms. I will also avoid going backwards, u turns much easier on parts. I am to understand that in 87 at least I have a larger frnt brg. That is good, but does not address the needles. I will definatly change the oil to synthetic. We changed the tranny oil when we did the clutch about 40,000 Kms ago and from what I recall of the plug it was pretty clean. We put in the reccomended dino oil and did the diff at the same time. I have the Red Line for the diff as well and will do that too. Those real cold winter mornings it does not like to shift to 2nd or 3rd till there is a bit of heat there. I am hoping that the red line will help that.

Paul
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asavage
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#10

Post by asavage » 12 years ago

plenzen wrote: I will also avoid going backwards, u turns much easier on parts.

AHAHAHAHA!

Several newer trucks, notably Mazda, have synchronized the reverse gear!

From the damage I've seen, it seems as if people are still crashing into Reverse, instead of the sane and normal practice of:
  • Come to a stop
  • Move shifter to any synchronized gear (eg 3rd)
  • Move shifter to Reverse
If the gears are not moving in relation to each other, they do not grind. All the damage I've seen in the few bad Nissan Reverse gears are tooth edge wear and breakage, which is due to incorrect shifting IMO.
I am to understand that in 87 at least I have a larger frnt brg.
Larger front countershaft brg, not larger front input shaft brg. See my notation in red at the lower edge of the picture above. Nissan enlarged one bearing only!
Those real cold winter mornings it does not like to shift to 2nd or 3rd till there is a bit of heat there. I am hoping that the red line will help that.
I would put money on it: cold shifting will improve with synthetic oil.
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.

greaseburner
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Location: southwest Manitoba, Canada

#11

Post by greaseburner » 12 years ago

Thanks guys. That's exactly the info I needed. I replaced the front bearing and pilot bearing last winter as I had to replace the clutch, so, that should be good. I'll be gone for a few weeks, but when I get back, I'll tear into her and look at the rear bearing and retaining nuts. Thanks again. :)
1987 Kingcab SD25
Dave

plenzen
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#12

Post by plenzen » 12 years ago

Learned the "Stop Everything Moving" technique when I was 16 and had my first (and only) 57 Chevy with a Hurst Mystery Shifter on the old Chevy 3 spd. Stuck with me ever since. In that case it was into 2nd and then into first or reverse so you did not embarrass yourself in front of your buddies. It continued on into the M21 as well, (2nd sliders in the old 3 spds would blow up a lot)
I still do it today even with the Nissan, into 3rd and then to first or reverse. Old habits I guess




Paul
Last edited by plenzen 12 years ago, edited 1 time in total.
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asavage
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#13

Post by asavage » 12 years ago

greaseburner wrote: I replaced the front bearing and pilot bearing last winter as I had to replace the clutch, so, that should be good.
When you say "front bearing", do you mean the clutch throwout bearing, the input shaft brg, or the countershaft brg? The latter is the weakest one and pretty much requires that the case be split to replace.

It's the brg that lives in the lower bore in this picture:
Image

Under cover No. 1 in this pic:
Image

It looks as if you can pull the front cover and replace that brg, but you can't. The front case has to come off.
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.

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ecomike
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Re: Tranny troubles

#14

Post by ecomike » 12 years ago

greaseburner wrote:Haven't had a chance to look at it yet, but this morning my tranny started to make a racket. Not a grinding noise. More like an out of balance shaft or something. And only in fifth. At first I thought maybe I was loosing 5th altogether, but that's not the case. All the other gears are fine. And fifth does work. It almost sounds like somethings hitting the driveshaft, but then it would be in all gears. I just did the clutch and pilot bearing about 8 months ago. BTW, I had some trouble before with slipping out of 5th if not under power. Any ideas??? I won't have achance to look at it until tomorrow, but suggestions can't hurt. Thanks :?:
I had the same problem with mine jumping out of fifth gear when not loaded, like when decelerating, or if I gently hit the brakes, for nearly a year before my rebuild. I also had vibration, but a lot of it turned out to be the drive shaft out of balance on mine (poorly built custom drive shaft), plus multiple well worn needle and main bearings through out the tranny. As I recall it had either a chipped tooth or two on the 5th gear. It also jumped out of reverse the last few days before I pulled it and rebuilt it. The reverse gear was missing an entire tooth by that point. Probably because some ignorant driver ( hmmm?) did not know how to shift into reverse, by shifting into third first! Thanks for hint guys!!!!!

Perhaps synthetic gear oil will help these beasts (trannys) last a bit longer!?
Regards,

Mike

1985 Jeep Cherokee Pioneer, 2WD, retrofitted with SD-22 & 5 spd manual trans, a 4X4 Gas Wagoneer ltd. (XJ) Jeep, 4.0 L w/ AW4 auto, and now 2 spare 2wd Jeeps, 87 & 89.

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