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Diff Lock Mod as a troubleshooting step??

8K views 8 replies 6 participants last post by  Patrix 
#1 ·
I am not very versed in mechanics especially when it comes to engines and transmissions. To me this is way outside of my comfort zone. Unfortunately I have reached a point in my project where I found that I cannot shift into super low gear. From my reading I have found that there are 2 gears on the same shaft and they could be seized and I might need to take the side cover off to take a look. I was first going to remove the cable and see if I can move the lever by hand without it connected in hopes that its just a cable. My question is since I cannot operate the diff lock until I can get it into super low should I do the diff lock mod to bypass this to check on the function of the front transmission (terminology correct here?) I understand the concept of doing this however am not sure if this is a good idea to do or if I would be adding more wear and tear to the machine by adding a "feature" that it didn't have before. Is the diff lock mod a good idea in general? I am very weary of getting into the transmission but will if I have to. I think I will need super low gear as I really only plan on plowing a 350 ft driveway up a small hill and pulling a 4x8 very light utility trailer full of barrels of leaves to the curb as well as other misc yard work.

I just bought oil for the machine and plan on doing the front dif and the engine oil once everything is put back together (suspension). Would it be wise for me to wait to do all fluid changes until the end or does it not matter. I was going to wait to do the engine oil change because if I understood in my reading the oil is shared between the engine and transmission so I will just be wasting quite a bit of money if I change it now and I have to take the side cover off. The front transmission however I don't know if it matters if I change it or not. I haven't done much reading on it other than how to change the fluid. I know it works in 4WD but am unsure of the locking diff part works as well. Like I said I am very limited in my knowledge of this area and only know what I could comprehend in my reading. Any assistance would be appreciated.
 
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#4 ·
I don't think that is the problem on super low.....it only effects going into diff lock.
 
#5 ·
The diff lock mod is very easy to do. I don't use diff lock often outside super low but haven't had any issue's yet. The only plus to doing this for me was it makes it slightly easier to shift. I'm unsure how it will help you troubleshoot. The only thing this would tell you is if the front differential locker works. Either way there are videos online showing how to do this.

If rocking it doesn't work. Try shifting into 1st gear then shifting to super low while bumping the throttle or driving slow off throttle. Mine doesn't always shift easily. When it's in gear it is easier to shift into high low or superlow.

Sometimes it is a pain to shift these quads. Their gears are the old style unsynchronized straight cut gears. Tough as hell but harder to shift and noisier.

The engine transmission sub transmission and rear diff are all built into the engine case and share oil. Make sure to use oil that is compatible with wet clutches.
 
#6 · (Edited)
The diff lock mod will not harm your bike if you are careful with it’s use. This is not confirmed, but I will only utilize diff lock in low or super and at speeds no more then 20 KPH (12 MPH) to avoid possible damage to certain parts moving quickly. Again, there is no proof going any faster will do any damage, but I don’t take the chance.

And the proper terminology your looking for for front transmission is (Front Differential). And unlike the engine and rear transmission, the front differential utilizes a Hypoid gear oil, (80/90). The engine/transmission utilizes 10W40 motorcycle oil. Make sure your oil is JASO-MA approved when you change it.

As for your differential lock not working, try rocking your bike back and forth as mentioned while trying to shift into gear. Also check the gear oil level in the front diff and make sure it’s not low or non existent. If all is good with the level, try disconnecting the shift linkage directly at the front diff and moving it by hand to see if it’ll engage. If it won’t engage that way, then you may have an internal issue within the front differential. But whether you chose to do the diff lock mod for troubleshooting purposes or just for overall versatility. Either way, once you’ve done it it’s a great mod to have.


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#7 · (Edited)
Thank you everyone for your quick and helpful replies. I will for sure try the rocking back and forth thing once I get it back on the ground.

I plan on putting Valvoline 80w90 GL-5 gear oil in the front differential as that is what I found at the parts store. Just for anyone who is looking for the size of the drain nut like I was, it is a 21MM bolt head. Surprisingly the service manual does not show sizes for anything. It gives the part a name and points to it in a photo which is helpful for us visual learners however not as helpful as saying use your 21mm socked to remove the bolt pictures in figure 21. The fill hole nut is a 17mm and is on the passenger side of the unit.

I was taking off the plastics yesterday and was then able to see the mechanics of shifting the differential to the different gears and saw that they were quite rusty and needed some TLC to allow them to shift smoother. I took a wire wheel to the metal teeth (grooved piece that locks it in each setting) to remove all the rust and polish out the metal. I will end up putting some grease here as well once I put everything back together in hopes that it stays smooth and rust free.

As for the oil in the engine and transmission I bought some Mobile 1 Motorcycle oil that says it is supposed to be used in wet clutch situations. I think I will wait to change the fluids all the way around until after it is all put back together.

Fandom fun fact for you guys to laugh at me at. Once I got the bike home and off the trailer I drove it around and my wife said what is that green fluid dripping underneath it. Based on the look of it I said it looks like coolant, great another thing to worry about. Turns out it was tire sealant coming out the really bad cracked tires. I thought the machine had a radiator and was leaking. Turns out it doesnt have a radiator and I made up a whole problem based on the look of the fluid that this machine cant possibly have. Shows you how much I know.I can confidently say it is a lot less of a mystery to me
 
#8 ·
Just for the record, the main reason diff-lock is available only at the super low is that locking the front wheels together is very stressful on the gears and CV/U-joints. While it may not harm anything to go fast in a straight line, turning with diff-lock on is difficult and would add extra stress if moving fast. The CV/U-joints are a weak point, as is the front differential gearing.


I have an 89 that is very difficult to get into super low and diff-lock, usually takes rocking it back and forth a few times with each lever.

My 1990 shifts easier to superlow, but once in a while it is difficult to diff-lock it. Again, just rocking the machine back and forth or bumping the throttle while in first gear.
 
#9 ·
I just bought my first brand new quadrunner 1987 4wd. :p The ''transmission'' didn't work on jack stand. But when it was running by him self, everything went good (diff lock). This ATV must ''move'' to pass to another gear.

By the way, got to rebuild the front brake completely (suzuki swift brake cylinder, way cheaper! ;) ) un-freeze rear brake, change intake valve (the rocker ajustement was way too far!!) new battery, undo some electrical mod that was made by a previous owner, oil and filter change (after 5 minutes of running on stand, the oil is already blacK!!! so another oil and filter change is done) front diff oil change (was slushi), one rear wheel bearing and one in front, voltage regulator, carb rebuild, and some love everywhere! :p

The starter didn't work (motor turn but not crank motor) So the one-way bearing is defect (starter clutch) I read somewhere about a guy after trying to remove starter clutch nut and fail with an impact.... After that the one way bearing was working.

Didnt have to go there... with the oil change, and runnning 10-15 min, and sitting on garage for 1 week after running, the one way bearing work! Starter work perfectly!

Will do he diff lock mod since it's just a pin in the lever body and all the plastic are out a this time. It will be so easy!

These quad are beast! Love the old stuff!

 
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