My thoughts on d300's

[jeeping1974]

I'm seriusly considering swapping my 208 for a flipped, twin sticked, low geared, heavy output shafted 300. It sounds like exactly what I need.

I wouldn't install 4:1 gears into the D300 with it going in a FSJ unless you plan on cutting out some weight. In a wrangler, I would do it because of the weight. Once you install a lower gearing in the t-case, the t-case will take more of the stress from the axles. In a light weight rig, the chances of you breaking something is unlikely, but not impossible. In a FSJ, you could strip out a get set or worse. I would stick to just the twin stick, HD outputs and clocking ring. Thats what I did in my rig and went with 1350 non-CV yokes all around.

[jeeping1974]

ive been working feeverishly for the last 6 moths swapping a new drivetrain under my fsj...i kinda planned it all around the d 300. i went with a doubler and 203, 700r4 in front of that, and finally said goodbye to the 401 for a 350. the case is nice and small and tucks up into the jeep body far better than the quadratrac. ill post a buildup thread someday.

The D300 is also 30 pounds lighter that a QT case.

[jeeping1974]

The J10 I just bought has a twin sticked Dana 300 in it. This may be the dumbest question ever, but even with the twin sticks the transmission (727) needs to be in Neutral before shifting the transfer case, right?

Yes.

[dusty]

I wouldn't install 4:1 gears into the D300 with it going in a FSJ unless you plan on cutting out some weight. In a wrangler, I would do it because of the weight. Once you install a lower gearing in the t-case, the t-case will take more of the stress from the axles. In a light weight rig, the chances of you breaking something is unlikely, but not impossible. In a FSJ, you could strip out a get set or worse. I would stick to just the twin stick, HD outputs and clocking ring. Thats what I did in my rig and went with 1350 non-CV yokes all around.

FYI I am running 4:1 in my cherokee chief with the 4bt after stripping out the stock small gear in low range pulling a trailer up to the ranch. I would put the jb conversions lomax 4:1 gears up against the stock dana 300 gears. I have had several stock dana gears crack on customers and then mine cracked with absolutely no abuse just let loose while pulling a trailer. and when you disassemble the 300 you can see why the cast gears are recessed the jb gears are imho a lot stronger so far so good 3 years a healthy 401, Now a 4bta, and a fair amount of dirt road, steep grade trailer tugging and lots o miles and so far so good.

My buddy is running a TPI 350hp cheby 350, a NV4500, Klune and a D300 with 4:1 and 32 spline outputs in a Toyota 4 runner sporting 4 links, full exocage, Corp 14 and Dana 60 on 46's tipping the scales a 5300 lbs Id suspect that if ever a D300 were going to break that'd probably be the one especially since it's been through little sluice just about every third weekend through the last three summers.

[jeeping1974]

You guys have had some luck then. (edit ->) That is impressive actually. (<- edit) I have seen local guys wheeling with 4:1 kits in their D300s and have the gears let go. It could be the kit they got was not up to par. I do know that JB's kit is really beefy, maybe none of them were running it though.

[dusty]

You guys have had some luck then. (edit ->) That is impressive actually. (<- edit) I have seen local guys wheeling with 4:1 kits in their D300s and have the gears let go. It could be the kit they got was not up to par. I do know that JB's kit is really beefy, maybe none of them were running it though.

I won't EVER RUN NOR RECOMMEND to anyone that they run Teralow gears EVER AGAIN.

I know i stripped out my teralows doing nothing strainuous 33's T-18. Absolutely stripped out and blew apart. no warning Garbage and after looking at them i can definatley call their 4:1 gears IMHO absolute CRAP....................I was running stock dana 300 outputs i figured they would twist and break before the gears and i was running 1310 u joints both of which should have popped LONG before the gears stripped... when the gears strip they usually break, lodge pieces of themselves between the case and the gear and then crack the case.

I know of 8 other guys locally who also had their tera's either in Dana 20's or in dana 300's strip out like mine did. Cheap crap. The Lomax gears were side by side a defiante improvement in the design.

I shocked when my stock dana gear cracked. the Tera gears though thicker than stock were not a huge improvement the mettalugy does not look as high a quality as the jb stuff obviously they proved to me their inferiority.

I honestly think Mike should have stepped up to an Atlas by now

[2006rubicon]

TH-400 atypical output shaft compatabilities

for bolting one up to a TH400 you will need a TH400/208 adaptor housing and the output shaft out of the same TH400. get the 32 spline input gear and the clocking ring from JB Conversions. their input shafts fit perfectly onto my TH400.

Hey guys! New poster here just got my first FSJ toy project started! I have a question, I have a TH400/454 out of an RV that I'm swapping into my 88 waggie. The thing is, this thing came with a drum brake E-brake on the tailshaft instead of the standard 32 spline slip yoke, does anyone know if it the same length output shaft as the more typical setup? How are these shafts measured? see pic to see what I mean, it's a wierd setup! (apologies if it does not upload, dumb FNG here!)
Also, Has anyone else done a big block swap? What would you recommend for engine mounts, solid or rubber? Have been advised solid mounts shake too much and can cause fatigue cracks in frame welds. Any other insights would also be GREATLY appreciated!

[Heimeken]

First of all, welcome to the forum, I don't know the answer but you should probably start a new thread for your question.

[cajun_lad]

First of all, welcome to the forum, I don't know the answer but you should probably start a new thread for your question.

Talk about waking the dead. Did you see when that last post was made? August...2009

[jaber]

Back on topic here, looking at the outside, the 300 case looks just like a D20 case, with a different input pattern. Are the internals the same? I know most of the D18 and D20s are interchangeable as for gears and such, is the 300 any different?

[Sambo]

the internals in the 300 are alot diffrent than that of a d18/20.size and thickness.
i wouldnt run tera low gears either.jb low max would be the way to go

[PalmerBS]

for bolting one up to a TH400 you will need a TH400/208 adaptor housing and the output shaft out of the same TH400. get the 32 spline input gear and the clocking ring from JB Conversions. their input shafts fit perfectly onto my TH400. plus the clocking ring will help you to lay the dana 300 almost perfectly flat between the fram rails.

you can run a 2.5" exhaust on the passenger side but the inner side of the exhuast pipe should be flatened a little to give a little more space between the dana 300 and the pipe.

i have mine installed in a 74 j10 with dana 44s front and rear. the driveshafts will bolt right up. the rear shaft will work fine if your running a 4" lift. the front will work fine if you are stock height. a little difference in height, the drive shafts will probably still work but you could run into something breaking if the suspension is fully compressed (rear) or fully extended (front) take the time to do some measuring.

i'll be installing a set of j20 axles in my j10 in the next week or two so i'll post up about the driveshafts then. i have yet to run mine so i have no feed back on that, yet.

Here's where I'm at with it. 78 Chief, rebuilt 401, rebuilt T400 w/ novak adapter to D300. CUCV tons, Dana 60 front/14 bolt corporate rear. 6" BJs offroad springs & due to D60 being spring over I flipped back.

Basically I'm sitting on 11" - 12" of total lift on this rig and what I didn't plan well for is driveshafts. I'm looking for any and all help on driveshaft options w/ the D300 and the best position to clock it?

Any help will be rewarded with many thanks!

[orangecherokee]

How do you know your driveshafts won't work? have you already put them in and flexed it out? I recently put a new shaft in mine and I had to stretch it out before I found that I had an issue.

You could also run a bigger yoke and get a better angle that way from the joint.