Tranny sludge??

[fuel tanker man]

I have a '94 Harley Davidson with a Dyna 5 speed gear box.

The bike has 16K miles on it now, and has been ridden rather easily from what I can discern. The previous owner said that for the last 7k miles it has been going into neutral on the downshift from 4th to 3rd gear every now and then. I've put 2K on the bike since I've owned it and I have noticed this happening on occasion.

I've asked on a few tech forums as to what might be causing this and the answers are as varied as the folks giving them; there is no consensus. I hear "bent shifter fork, something about the 'dogs', poor shifting technique, all the way to "Dyna 5 speeds just do that."

I think if it were anything bent, it would do it all the time, and it doesn't. It could be excessive wear on a cog, but the problem doesn't seem to be worsening as that scenario would likely entail. I do know of two other Harley riders who mention this problem happening on thier bikes. One has been exhibiting the problem for about 20K miles (with 40K currently on the odometer).

My bike's tranny has always been run on Harley semi-syn transmission lube--at least up until about 1600 miles ago. At that point I switched to Mobil 1 75W90 to see if the downshift problem would go away. After going to the Mobil 1, I did not notice the downshifting problem for the first 1000 miles or so; it seemed to help. But now it's doing it again--every now and then, just like before.

My question is this: Is it possible that the trasmission is "sludged up" a bit? If I've read here correctly transmission lubes do not typically contain detergents, so this might not tend to keep the gear box clean. No?

I was thinking of changing the tranny lube out with a heavy engine oil which contains a healthy amount of detergent, and seeing what happens. Harley says that their 20W50 Syn3 can be used in the transmission. Amsoil recommends their 20W50 in the Harley tranny, as does Mobil 1 (V-Twin).

I've heretofore been a strong advocate of transmission specific lubes in the Harley gear boxes, but if it is determined that sludge could be the problem with my downshifts I might just change my mind.

Just wanted to try the easy things first before wrenchin' on her...

Dan

 

[hk33ka1]

I wonder if a product like Auto RX might help? Try looking around for some of Frank's (maker of Auto RX products) post's to see if it is an option.

http://www.auto-rx.com/index.html

 

[medic]

Seems kinda funny - everybody is blaming SYN3 for this problem and this bike has never had SYN3 in the tranny. I guess people need to blame something other than design problems.

FWIW, I have seen abused trannys, with >40k miles on the original fluid, where the fluid is black and there is no sludge in the tranny at all. It is almost impossible to bend a shift fork in this tranny and at this mileage, there should be minimal wear on the shift forks.

Personally, I would first look at the easy fix and maybe adjust the shift lever a bit. I think there may be one problem with this (My service manuals are all at work), which is the primary case will need to be removed to get to the adustment screw on the side of the tranny. Unless you are into this type of work, I would consult a dealer or a good harley mechanic. If you do decide to do it yourself, an official HD service manual (DO NOT use an aftermarket manual) will help out quite a bit.

Obviously, you aren't getting the bike all the way into 3rd gear or it is going past third gear - the easy way to tell is what gear is the bike in when you try to shift down again 2nd or third. If you are in 2nd, your are going by third and ending up in between 3rd and 2nd. If oyu are in 3rd, you just aren't getting all the way into third. The shift drum, by design, doesn't want to be in between gears, but from what you are describing, something is just slightly worn or out of adjustment - either can be fixed with a minor adjustment of the shift lever.

 

[fuel tanker man]

medic,

I think you're right. I did adjust the shift lever linkage, and will reprise part of a post I left at a Harley forum below:

...anyway, I first adjusted the shifter linkage to lengthen it one turn. I took the bike out for a short ride and it did the "neutral surprise" about three times almost immediately--way more than usual. I thought maybe I was on to something...

I figured I had gone the wrong way with the linkage.

I brought it back home and shortened the shifter rod two turns (one to make up for going the wrong direction, plus an extra turn). I took the bike back out for a ride and the problem seemed nearly cured. I had to really, really work to make it fail the downshift.

I brought it into the garage one more time and shortened the shift rod one more turn, and went out for a longer ride this time. So long as I'm riding normally and not making a concerted effort to "limp shift" the bike, it appears that the false neutral problem is almost totally cured.

Another thing I've noticed since shortening the shifter rod a couple turns is that my upshifts have a more positive "clunk" (like normal for a Harley). Prior to the adjustment, the tranny actually seemed to up-shift too smooth if that makes any sense. Most HD's I've ridden have a characteristic "chunck" into each gear. This bike is doing that now, like I believe it is supposed to do.

medic... I've ridden the bike about 500 miles since making this adjustment, and I think it may have hit the false neutral once, or twice at the most. It does go down PAST 3rd gear on the downshift, and I must pull up a bit on the shifter to help the tranny find 3rd. If I downshift again it goes into 2nd

! But as mentioned, it's not enough of a problem now to worry much with. A buddy of mine has a '92 Low Rider and he reports the same thing: misses 3rd on the downshift every once in a while; if he downshifts again it goes to second gear so his is going past 3rd on the downshift just like mine does. The problem seems to occur at a specific road speed at a specific RPM level--might be some kind of synchronizer problem.

I haven't tried shortening the shift linkage any further to see if I can get rid of the problem entirely, but I might try that in the future. This bike has pretty much been babied all its life, and with only 16K on it I wasn't ready to believe there was anything much wrong with the tranny--although that is of course possible since I've seen brand new bikes screw up...

For my purposes I'm happy with the performance of it now. This is apparently not uncommon with the early 90's Dyna 5 speeds. Other than my friend I have one other acquaintance who says his bike does this too. A couple of members on other forums have also mentioned this happening. Probably some sort of design flaw that Harley got straightened out in the late 90's.

One mechanic told me that "these bikes just do that." While he might be partially right, it does appear that adjusting the linkage can improve things quite a bit.

Dan

 

[medic]

This wasn't the adjustment I was talking about, but if it worked I'm happy and I'm sure you are too.

I was talking about the adjustment on the side of the tranny - it controls how far the the shift lever pulls or pushes the drum (cam).

The HD big twin 5 speed is a very simple design - almost too simple. A minor adjustment in one direction or the other can usually fix these minor shift problems. The problem is that on some bikes, harley didn't leave enough room behind the primary case to make adjustments. One that comes to mind is my old '86 FLHTC. I haven't had to do anything other than maint on my '93 FXSTC yet.

Quite a few people claim that harley trannys do this sort of thing and most people accept that. I don't accept it and the problem get fixed. My old shovel-head didn't leak oil when I got done with it. Most people accept that harleys leak oil.

 

[fuel tanker man]

Medic,

Where exactly is that adjustment and how difficult is it to set?

I'm just wondering if I should check mine just to be sure it's right...

Thanks,

Dan

 

[medic]

This would be on the left side of the tranny. As your are looking at the tranny, it would be just to the right of the shift arm.

Like I said, it may be immpossible to get to it without removing the primary case. It will be a threaded stud with a allen wrench fitting in the end. It will have a large nut around it to hold it in place once set. If you can get to it, loosen the nut, and then turn the stud about 1/8 of a turn to the right (for your problem), then tighten the nut back up, holding the stud in place the the allen wrench. This will be a blind adjustment, so you'll want to mark the stud for the original position in case it doesn't work. If the primary case needs to be removed, you may as well pull the top off of the tranny too so you can see how far the shift lever is pulling on the drum.

If you plan on pulling the primary case, I would highly reccomend the assistance of a service manual. It help you significantly. You'll also need a pnuematic impact wrench.