Dana 18 Small Hole vs Big Hole

Hello from Portland, OR!

I've just found this awesome forum resource, and I have been soaking up the knowledge since my T86 spun the cluster shaft.

I have a 1964 CJ5, with a 225 V6. Not sure if the V6 is native, the motor mounts are very nicely welded. Here are some pictures:
http://flickr.com/photos/sydolta/tags/jeep Some of them show the restoration.

So, I saw that Herm had a half dozen transmissions for sale, and he was nearby. After chatting, I think I've finalized on a T90, since my T86 had T90 guts, I figure just cut out the middle man!

Anyhoo, Herm really wants to sell me a small hole dana. I was kinda thinking I wanted a big hole dana, since thats what the factory put on em in 68+ (right?). Its set up for the V6.

What pitfalls are there with a small hole dana, other than the lack of Tera Gear upgrade, and maybe fewer trans swap options later? Every time I search I see "swap out the small hole for big hole dana". Novak history lesson says the guts are virtually identical.

Am I going about this all wrong or loosing sleep over nothing? I don't think Herm would steer me wrong, but the T90 was already set up for a small hole dana. I can understand him not wanting to work harder than required.

Thank you for your advice.

 

Only difference I am aware of is the larger center shaft. I have also heard the large hole case is stronger.
Keith

 

Do you have a transfer case already? what is it?

The T90 to big-hole t-case mating is a piece of cake. You just use a different bearing retainer in the back (the same one you must have already been using if you have a big-hole case?)

He probably has several small hole dana 18's already built.

 

Thanks for the response! Searching around the forums late last night (my head is a little spinny from all the t/tcase combinations here..) Someone mentioned/thought/I am halucinating a T86 retainer will work with a Big Hole D18 on the T90 :?).

I have a core Small Hole D18. I recall it having a 1 and 1/4 intermediate shaft diameter. From my untrained eyes, Something Bad happened to it at one point (PO), and nocked a large portion 80% of the front bearing supports out of the inside of the front case. Still ran ok though (well enough for me to not know :evil. Maybe I'll get pics next time when I see Herm.

Even if I did get a Small Hole case from Herm... is upgrading (later down the road) to a Big Hole D18 no biggie as far as maybe input/output Yokes (I think they are splined different :? ), and maybe a different gear on the (Herm's Souped-up Warn) Overdrive if required? That doesn't sound too bad then. I just don't want to be "locked in" to a Small Hole World. (cue annoying music) Do It Right The First Time!

As a newbie Jeeper here, I look around at "the cool kids" whom have done interesting transmission swaps/mods, they seem to usually have Big Hole D18s.

I think Herm is a little swamped right now also.. His work looks top notch, but that tradeoff of course costs time

 

If your swapping trans, a good easy swap would be a T14, and stick with the big hole transfercase. The t14 is very sim. to the t86 only a little stronger and has sincro first gear which is nice. the only diff. is its slightly longer, maby an inch, so trans boot has to move back slightly and rear drive shaft might have to be shortened a little. (I did the swap on my cj however and didn't) The T14 what was in :v6: cj's from 68ish up to 71 so it is even a stock trans.

As far as dana 18's as long as they have a 1 14" int. shaft, they should be fine, big or small hole, just more opptions with large hole i.e. t14.

Welcome aboard!

 

You are right on the t86 bearing retainer on T90 for big hole case.

the spline on the transmission output shaft and tooth count of the drive gear determine overdrive application. In your case, both would be 6 spline/29 tooth. So, no problem.

http://www.novak-adapt.com/knowledge/transfer_case_gears_grid.htm

the smaller intermediate shaft was on older dana 18's. no problem there either.

 

To me the big advantage to the large hole case is being able to separate the transfercase and transmission without removing the transmission drive gear.

 

...and being able to bolt it to the back of a Jeep T-18.

 

Thanks everyone for the input!

I think I'm understanding the differences between BH and SH now, and the FUD is starting to clear.

So far, only have the single Jeep. Just starting out. Someday, when I have a few more bills in my back pocket, and an opportunity presents itself, I will "upgrade" to T14 or T18 and another D18 and worry about all this again. That way I will have spares! And I'll know what to do!

Call me crazy, but before my T86 spun the shaft (maybe it was spun all along?), I had no complaints. (Disturbingly, before opening the '86 and seeing the "macaroni" shaped needle bearings, I could still drive it nearly the same as the day I bought it, 3+ years ago). I thought better and decided to rip into it.

I can only imagine what a new trans will feel like! R)

carnage pictures:





Full set / larger here:
http://www.flickr.com/photos/sydolta/sets/72157600528002310/

I think Herm's a sharp and friendly guy. He stands behind what he does, and from what I've seen of his work, its solid. When the '86 let go a few weeks ago, ECJ5 was instrumental in my transmission crash course.

Again, many thanks all.

 

So what years/engines had the big hole case? Thinking my 69 :v6: might have it.

 

If I remember right all the v6 Jeeps had the big hole case.

 

I recall I had to use the big hole d18 to install my warn overdrive...

 

shouldn't have...... I pulled my OD off of a small hole D-18 on put it on my big-hole

 

I thought I read that the very first year V6 didn't use the T-14 and thus would've had the small hole case.

 

Large hole cases started in 1966 and were standard with the t86 and t14 not the t90 though.

 

so if i am reading this right all T-90"s come with the small hole transfer case? going to be getting into this stuff myself and i dont know what i have yet,it is still all bolted together

 

If stock yes.