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D300 popping out of low range

This kind of problem has been discussed before but even so, I'm curious as to a solution. The other day I installed a d300 behind my t19. I never realized how much noise a properly operating d20 made compared to the quietness of a d300 (all gears having a helical cut will do that for you). I had replaced both poppet springs with the stiff kind (one original spring was softer and I replaced it) and even shimmed behind them a little bit.

In low range it slowly forces itself out of gear. I presume it is the low shift rail poppet that isn't holding when this happens. I also note that the plastic covers on the shifting forks, when installed, are so wide that there is no real clearance between the plastic and the sides of the channel in the collar and they can drag. One thought is that some clearance would be desirable as maybe the collar isn't really going that last few 10 thousandths forward to fully engage the poppet. It probably needs all the "detent" it can provide.

So in any case I'll need to pull the case and remove the front output bearing retainer. I'm also of a mind to re-install the original plastic covers - still in good shape - that I saved. I think there should be some clearance in that channel. Do I add more shims? I read where there's an overly strong poppet spring fix for this but it is so stiff that you really shouldn't go that route unless you really need it. Any other thoughts on this?

And yes, all new bearings set to 0.002" endplay, new im shaft and needle bearings and thrust washers, yadayada.
 

ScoutBurton

Member
Mark,

take a look at jb conversions, inc web site. Under Dana 300, their twin stick ball & spring kit. It will give you a good visual of the 2 bores, their different heights, and how they use a ball bearing to make the 2 bores the same height, and then use stiffer springs. I've installed several of these kits into Dana 300's and never had a popping out issue. As stated on the site, that isn't always the "guaranteed" fix, but most of time it is. Rarely, it can be excessive wear on the teeth on the front/rear outputs where the sliding collar engages, or the sliding collar teeth themselves. I wouldn't think the plastic shift fork tab clearance would affect this, but? You could almost certainly purchase the ball bearing and stiffer springs in jb's kit at your local hardware store for pennies on their dollars also. Hope this helps.
 
Mark,

take a look at jb conversions, inc web site. Under Dana 300, their twin stick ball & spring kit. It will give you a good visual of the 2 bores, their different heights, and how they use a ball bearing to make the 2 bores the same height, and then use stiffer springs. I've installed several of these kits into Dana 300's and never had a popping out issue. As stated on the site, that isn't always the "guaranteed" fix, but most of time it is. Rarely, it can be excessive wear on the teeth on the front/rear outputs where the sliding collar engages, or the sliding collar teeth themselves. I wouldn't think the plastic shift fork tab clearance would affect this, but? You could almost certainly purchase the ball bearing and stiffer springs in jb's kit at your local hardware store for pennies on their dollars also. Hope this helps.
Your comment about the ball bearing just rang a bell. When I took this d300 apart an extra ball bearing appeared in my haste disassembling it and I couldn't figure out where the heck it came from. I'll bet it was installed by a previous owner! Which rail poppet would that have gone to? The inner (low range) one?
 
I've read up on the problem and now need to decide how to fix it. Being previously ignorant, I saw that I had the stiff spring in the deep hole and a softer spring (red paint) in the shallow hole. I didn't know one hole was deep and the other shallow...so I got two new stiff springs from the vendor as a solution. Being very ignorant of things, I put a shim under the stiff spring (maybe the one in the shallow hole as well), making it somewhat stiffer, but apparently not stiff enough. On the other hand, I really made the other one super stiff, probably too much! But not enough to keep everything in gear in low range. My thought is to yank the t/c and front bearing retainer and remove the shims, put the 5/16" ball back into the deep hole with the stiff spring, and put the red spring back in with a 0.050" shim (found a great write-up on this approach on another site). This should make both poppet balls apply about the same amount of force. I'm also going to take the edge of a hand grinder and deepen the rear low notch(s) slightly, say, 0.020" or so. And of course, put heli-coils into the stripped holes in the t19 rear bearing retainer/adapter. Grrrrr!!
 

ScoutBurton

Member
That sounds like a good plan Mark. I think that deepening the detent notch on the shift rail will definitely help. Along with putting the 5/16 ball bearing back in the deeper bore and making both springs a little stiffer. Will hopefully solve your problem! Let us know.
 
I posted my gripe over on the BP. This week put the 5/16" ball bearing under the rear shift rail poppet, and slightly deepened the rail's notches. Still pops out, just not as quickly.

Stumped as to where to go from here.
 

ihpartsjeff

Administrator & Owner
Staff member
If memory serves me correct you are running a T19 transmission? Are you using an actual manual D300 bull gear? Or is it an auto D300 bull gear that has been resplined for the manual transmission?
 
If memory serves me correct you are running a T19 transmission? Are you using an actual manual D300 bull gear? Or is it an auto D300 bull gear that has been resplined for the manual transmission?
No, it's the correct bull gear. We've got a discussion going on BP that may have honed in on a solution that may address the problems with worn parts. Next time you have one of these critters apart in your shop, would you mind getting a few measurements for us?
 

ihpartsjeff

Administrator & Owner
Staff member
No, it's the correct bull gear. We've got a discussion going on BP that may have honed in on a solution that may address the problems with worn parts. Next time you have one of these critters apart in your shop, would you mind getting a few measurements for us?
Which part? We have new shift rails in stock.
 
Which part? We have new shift rails in stock.
We are looking at machining a pocket 0.008" deep in the thick thrust washer that is held in place by the bearing cone (rear output) to reduce the axial play of the clutch gear back to the spec'd 0.005-0.010" (I guess that's what it is called - the large gear for low range). It would then clear the splines or hub the collar rests on. I would place a shim of comparable thickness between the washer and the cone so the geometry of the cone isn't disturbed. Mine, like many or most with miles on them, are running around 0.014" and that creates the wobble that causes it to pop out. That's the theory, anyhow. I would need the diameter of the journal the cone is pressed on to see what shim could clear. I'm thinking something like a pinion gear shim might work. This, plus the stiffer springs (I swapped out the lighter front spring for the same one as used on the rear).

We're all just applying our creative juices to solving problems with old trucks!
 
I misspoke. Thrust washer would then clear the clutch gear journal. The shim i think of adding might just be one used for setting endplay. Have to consult the exploded diagram again
 

Hondo

Member
I ended up twin sticking mine. Wanted more resistance to help keep it from popping out, so ended up using some fairly large, rough, hardened flat washers between the two shift arms and the ear on the transfer case, also reduces wear on the aluminum ear. Added some Belleville spring washers outside the shifter arms to provide adjustable pressure to the stack. The aircraft nut that goes on the end of the ½ -20 bolt can then be adjusted to add quite a bit of resistance to the shifter arms movements. Haven’t had it pop out since doing this. It does take some patience to get all the washers, shifter arms, bolt, and nut installed, but it's worked well for me. Do yourself a favor and drill/punch an access hole in the tunnel if you haven't already. The threaded end of the bolt does not thread into the second ear, it is just kind of resting in there for additional support. The 5/16 bolt that normally retains the pin for the single shift arm keeps the bolt from rotating. The twin stick kit isn't really cheap, but less painful than pulling the tranny and transfer case out.
 

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