Dana 18 upgrade...need opinions

I had the old/new flatty out this weekend and found my first weak point. I'd like to know if you all think this might be a fluke or something I'm gonna be doing all the time. I've ordered the new replacement gear and I'm planning on having the whole case Cryogenically treated. They boast a 30% improvement on tensile strength and 100 percent on wear. I read a few old threads on here about the D18 surviving 400 horsepower and small V-8's, and I'm nowhere near that realm. Did I just have a bad day with this one?

 

Also, this is the Dana 18 with the 39 tooth (broken) gear behind an SM465 and a TBI 4.3.

 

just depends on your driving, more or less.
anything can be broken, at any time or place, given the right circumstances.

 

I’ve been pretty mean to mine and it’s survived well so far.

 

I'm running a Dana 18 behind an SM465 with a 283 SBC. I've got 60's f/r and 36" tires with no problems yet. I'd call it a fluke and rebuild it.

Extreem

 

Nickmil has one for sale right now, IIRC.

 

I have another out there rusting away as a spare. Not that I'm turning something down, I just don't think I need it yet. Keep the opinions coming, though. I'd like to hear them all. I'm feeling better about my 18 already.

 

I stripped two sets of gears just like you have pictured behind a stock 360 and t18 fwiw. Although both times it happened I was romping on it, one was a quick 1-2 shift and the other I bounced and didnt let out of the gas. The third set was still working well the day I sold it.

 

Yep, mine surviving just fine behind not too mild 381 sbc. That said, I drive off-road like the old man I am and am only running 33's. I would suggest that you rebuild using a case from a D20-substantially more iron, and put in a set of terra low gears. I really like the terra lows-they were well worth the expense.

 

I'm thinking I'll disassemble it, check everything over good including the intermediate shaft, install new gear, have it cryoed, and then maybe install the Dana 18 girdle and go from there. If that doesn't work, I'll have to find a D20 box and start from there. I like the Terra low gears, especially the crawl ratio, but pretty pricey. That's plan C.

 

yeah make sure everything is tight and the intermediate shaft isnt worn. A loose mesh might have put more stress on the outside of the teeth

 

A friend of my broke his dana 18 once. I had a 20 case, upgraded rear output shaft and a lower gear set(not sure if it was terra). It was behind an sm435 behind a stock ford 302 in an fj-40.

I'm not sure if it was unstucking a 7000 lbs ford from a snowdrift, or the 10 people that rode on it back up the hill, but the gears gave up the ghost on the way off the trail.

A strong transfercase that still has an offset rear output would be an fj-55 case. I've seen one survive in a rig that broke the input shaft on it's sm420.

 

I used a dana 20 caseand put all the dana 18 guts and stuff in it. The dana 20 has a thicker casting than most of the 18's.. Not that it will help your broken gear situation but it is an overall improvement.

 

I'll have to look up that FJ55 case. I'm not familiar with it. The path I'm leaning towards now is buying a buddy's Dana 20 for 150 bucks, and ordering Herm's Terra low kit, swapping all my 18 stuff into it and then cryo dipping the whole thing. That would run about 1000 bucks. In the mean time, I think I'm still gonna replace that one broken gear and take it out again and see what happens. This is still too much money for a 63 year old transfer case, but I'm not sure where to go from here.

 

Herm's Tera-low kit and rebuild kit ordered. I decided against the new Dana 20 case only for money reasons. I'm sure I have plenty of questions coming soon.

 

I thought the D18 and the D20 transfer cases were about the same strength. And the D18 has a lower low gear.

But a D20 with a Tarra Low kit is way cool. Or just go all the way and get an Atlas or Stak...........

 

the early 18's had a thinner case.. the later ones had the same thickness as the 20 but the later 20's had better castings.

BUBBA

 

Yup, I agree.
One thing you want to watch out for on the 20 cases is the location of the fill plug if running the stock parking brake and make sure it has the casting boss for the clutch pivot. Not all of them do and many of the 20 cases have the fill plug on the back instead of the passenger side. Most can be drilled and tapped but something to watch for.

 

Here's mine. V-6 SM465 and 17year old popping the clutch at 3000rpms in low range.

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Here is a griddle I had a friend made for me. He made two other for other friends.



My transfer case held up after I dumped the clutch @ 6000rmp.
I blew up my Muncie M21 transmission instead.