[doonze]

Ok, so I picked up my first quad last week. It's an 88 TRX300FW. Runs really well. Story on the bike is it was a parts bike the seller got when he bought the bike it's parts had been used to rebuild. Mainly they had pulled the rear end out of this bike and put it in the other one. They gave him both bikes when he bought the running one.

As providence would have it, he later realized he had a spare 300 rear end laying in a parts pile in the back of his garage. So he decided to throw that in, and see if the bike would run. Turns out it did. Runs really well for a 31 year old bike really. I'm still fine tuning the carb, but it starts, runs, idles, and shifts good. No smoke, no leaks. He also replaced the front bearings, brakes, and brushes in the starter. Tank is rust free. Plastic is weathered all to heck and pretty ruff. But that's the least of my worries.

Ok, enough story time. So I noticed since I got it that it pops/clunks when turning sharply. I ordered Mobile 1 75w-90 LS for the diff's and transfer case (yes I know it calls for 10w-40 for the transfer case, but I've heard good things about using gear oil as well), air filter, oil filter, spark plug, Mobil 1 10w-40 motorcycle oil, DOT 4 brake fluid, and 4 Kenda Bear Claws (F 24x9x11 R 25x10x11 I also know that's 1" oversized, but I wanted a bit more clearance and tire than stock).


So I got everything but the rear tires in today, and spent the day changing every fluid, plug, and filter. Including bleeding the brakes. Every fluid came out back as could be, and the gear oil came out like gray goo, I don't even think he changed the rear diff fluid when we put the new rear end in! Also, when trying to adjust the brakes I could barely even turn the front tires with the whole front in the air. After a bit I raised all four tires off the ground, and I could move the fronts a whole lot easier, but all four ties spun when I turned the fronts, so still to much resistance to really adjust the front brakes.

What all this tells me is that my front diff clutches are pretty much fused. So now I'm finally coming to my question. (Sorry took so long, just wanted to give the whole picture) The Mobile 1 75W-90 is supposed to have friction modifier in it. Does it take time for it to "unfuse" the clutches? Or should it have been pretty much instant? Should I go out and get some GM friction Modifier and just throw and ounce in now? Or wait?

Any input is greatly appreciated.

Thanks!

 

[shadetree]

80w-90 gear oil, and your over thinking this. use nothing but gear oil...do not use any kind of auto oil in the front or rear diffs !!. the transfer case ( right in front of motor )..you can run auto oil in this ?, but I recommend using 80w-90 gear oil in there as well. front diffs are limited slip. unless its clanking when your turning ?, then this would be the cv joints in the front drive axles, not the front diff !. very seldom do I ever see a front diff in a trx300 go bad ?. maybe bearings ?, but never clutches !.

 

[doonze]

Oh no! I used 75w-90 Mobile 1 gear oil in the front and rear diff for sure! I just ALSO used it in the transfer case. It's hard to tell, but I think my front limited-slip clutches are loosening up a bit with the new gear oil. I might throw some GM Limited Slip friction modifier in there as well. We'll see. I'll post back about it after some time and miles.

 

[Goober]

I use BelRay 80W-90 hypoid gear oil. My first quad popped a little up front — oil was too low to tell color — changed it and ran it for a few days and changed it again. No problems since. My latest project popped too for same reason when i get it running I’ll do a second change. Get some heat in that oil to help clean out the case.

Yes the front and rear drives are all locked together. Do you have it on a motorcycle lift? You can use a tire iron to turn all the wheels just be careful you’re not putting more torque on the wheel nuts.

 

[retro]

The Mobil 1 LS gear oil you used in both diffs is fine. Don't add any more LS additives to them. You may have to drain those diffs a few times to get them cleaned out. It sounds like they both need a good flushing though. I'd flush them out now if I were you.

 

[doonze]

I use BelRay 80W-90 hypoid gear oil. My first quad popped a little up front – oil was too low to tell color – changed it and ran it for a few days and changed it again. No problems since. My latest project popped too for same reason when i get it running I’ll do a second change. Get some heat in that oil to help clean out the case.

Yes the front and rear drives are all locked together. Do you have it on a motorcycle lift? You can use a tire iron to turn all the wheels just be careful you’re not putting more torque on the wheel nuts.

I don't, but it's on the list now that I have this quad. I never needed it for my bikes. I did have it up in the air with two jacks and some jack stands, but it wasn't super stable. I'm not sure exactly how one test the front brake adjustment on these since spinning any tire adds the drag of the entire drive train. Guess I'll just have to play... Thanks for the tips!

The Mobil 1 LS gear oil you used in both diffs is fine. Don't add any more LS additives to them. You may have to drain those diffs a few times to get them cleaned out. It sounds like they both need a good flushing though. I'd flush them out now if I were you.

My boss borrowed it for a trip his family it taking to Colorado this week. I'm expecting them to put some good miles on it. Once I get it back I'm going to flush everything again. Good advice!

The PO said he did the front bearings so I'm thinking those are fine, however it could be my shafts I suppose. I really don't know enough about these yet to tell if it's the front diff, CV joints, or bearings. I'm not apposed to replacing stuff without 100% verification. It IS 31 years old, any wear item I have to replace I see as PM, less to go wrong down the road. However, there are other projects first (clutch and master cylinder for example)

I appreciate all the input and advice. I was expecting there to be an overwhelming amount of info out there on these. But honestly I'm find info scarce. And parts hard to find.

 

[GirlsRideToo]

^^^ diff flush.

You said the PO replaced the bearings but I'm assuming you do not know if the bearings were OEM. Bad bearings go bad quickly. Even good bearings will not last as long as they should if they are not packed properly with grease. It seems even OEM bearings do not arrive to you packed properly. This has been discussed many times on this forum. @retro taught me how to pack them properly.

The popping noise with sharp turning is a common issue discussed here. The problem is typically bad CV joints, as @shadetree said. I had this very problem on my 2014 Rancher 420FM.

 

[fishfiles]

You think the noise could be from the front drive shaft spline at the pinion slipping , seen that a few times now

 

[doonze]

^^^ diff flush.

You said the PO replaced the bearings but I'm assuming you do not know if the bearings were OEM. Bad bearings go bad quickly. Even good bearings will not last as long as they should if they are not packed properly with grease. It seems even OEM bearings do not arrive to you packed properly. This has been discussed many times on this forum. @retro taught me how to pack them properly.

The popping noise with sharp turning is a common issue discussed here. The problem is typically bad CV joints, as @shadetree said. I had this very problem on my 2014 Rancher 420FM.

I'm kinda going through this thing and replacing all wear items. I got it cheap enough I can justify spending some extra money to refresh everything. I really feel the PO's only replaced things when they failed. I likely will just get new CV's, bearings, and tire rod ends. Just to have it done and out of the way. Plus that will take problem items out of the equation. I'd rather do all this while it's still new and I'm still excited about it, seems not to be such a chore then!! LOL

You think the noise could be from the front drive shaft spline at the pinion slipping , seen that a few times now

How would I tell?


In other news, since I replaced the front diff fluid, I think it's been leaking out the bottom of the diff. The new "non-sludge" synthetic fluid may have been light enough to find it's way through the gasket. I'm not 100% on this, but when I got it I had no leaks, now it seems I do. It COULD still be oil/fluid running around the skid plates from my oil change/diff fluid change. I didn't have a funnel handy when doing the oil and got a bit on the plate. And the diffs drained about 1/2 what was in them onto their plates. But I really feel I've got multiple leaks since changing all the fluids. I guess I need to get a true ATV lift and start removing skid plates to verify.

 

[fishfiles]

jack all 4 wheels of the ground and turn the front tires by hand and by engine power --- does your bike have the 2 inch shock absorber lift in it ?

I would check the oil levels again if you think you have a leak

 

[Goober]

You have to remove the diff guards to drain the diff using the oil drain bolt. At least i couldn’t find a way to access the drain bolt without removing the guards. Uhhh did you remove the wrong bolts?

Yes this first year TRX300 may require some diligent parts hunting. Use the service manual and parts links to get to know your quad better and practice parts hunting. Set up some parts searches on fleabay. Only buy OEM parts or used parts the seller states came off of a model matching quad.

I have to do the same with my 86

 

[KoolBreeze]

I’ve been chasing a front end pop for a while on my ‘88 350. Have replaced the CV axles twice with used ones (and repacked them), replaced every bearing and seal in the front end, took the clutch packs apart and cleaned and soaked them in oil, and it was still popping a little last time I was on it. If I was doing it again today, I’d replace the clutch packs, as I think that’s what is the problem with mine. They were on the high side of the torque spec when a reassembled them, even after cleaning and soaking them in oil. I do intend to try some friction modifier but don’t use hardly any during the summer and just haven’t gotten around to it yet. Good luck.

 

[Goober]

Here’s a pic of how i load up the diffs using an oil squirter. Oil in the diff Stays level on a bike lift
If you roll the wheels while your filling the ring will suck the oil into the diff. Then you wait for it to level and top it off

 

[doonze]

Thanks for all the advice! I'll be going through at least the rear again as it's developed a leak where the left axle goes into the diff. I'm also going to top off the front using the tire spin trick!

I got it back today, my boss had borrowed it and took it on a 6 day ATV camping trip in Colorado. It seems all those ruff miles finally freed up the front clutches. It doesn't seem to be popping anymore! But I'll need a bit more time with it to be sure. But right off the bat it seemed to steer much better.

And of the 6 UTV's and ATV they took (most newer), guess which one was the only one they never had to work on, and had zero problems with?? Yep, the 31 year old Honda 300! Ha!