D30 and 37" tires

[Stu Olson]

I was at TBT's shop yesterday doing a little work and my buddy stopped by and dropped off his TJ. For the past two years, he has been pushing 37" MT/Rs on an ARB equipped D30/D44 combination. Not too long ago, he took out the short side shaft on the D30 (stock axle shafts). He picked up some alloy shafts (Superior brand....I forget) as the splines on the stock shafts were quite twisted. I don't remember if he also got CTMs or not...I know he was thinking about it. He did not have a Warn hub kit.

Anyway, his D30 R&P blew the while he was wheelin' in New Mexico last week....but it appears that the shafts survived (they will know for sure when they pull it). There are some bets going around that his ARB lost the battle too....won't know until it is opened up.

I realize this is not earth shattering news....D30 and 37" tires are not an ideal combination.....but I thought I would just pass it along as another data point. Over the past couple of years, the trail difficulty he has been running has increased and he obviously found the point where something more than a D30 is required.

[jeepik]

37 inch MT/R weighs less then my 35 inch Krawler and less then some 35 inch Swampers

and people get away with it

point is people break dana 30's with 33's too and some people use their dana 30's with 37's without issues

anything can break

[John]

What ever became of that test with the cryo-treated ring and pinion?

[Stu Olson]

Originally posted by jeepik
37 inch MT/R weighs less then my 35 inch Krawler and less then some 35 inch Swampers

and people get away with it

point is people break dana 30's with 33's too and some people use their dana 30's with 37's without issues

anything can break

Anything can break and people get away with all kinds of stuff....no doubt about it....my buddy did for 2 years.....and people break things with 33" and smaller tires....they sure do. But that was not the point I was attempting to make.

The point I was making was that the R&P went. A number of the guys I have Jeeped with (and in our club for that matter) have broken stock D30 shafts. Very few that I Jeep with that have alloy shafts break them. I've never been on the trail when someone's D30 R&P went and I rarely see anything posted on the club's BBS concerning it.

A number of rock crawling folks that frequent this board, myself included, use the small Warn hubs as the "intended" fuse....to save the expense of an R&P and possible differential replacement....and my buddy had not gone that route yet.

To clarify.....alloy axle shafts and bigger tires push the weak link to the R&P. I'm sure he probably would have had the same results with your Krawler tires too.

Sorry I didn't make my point more clear in my first post.

[Darrell C]

Interesting.

I wonder how much stronger a D44 center section is compared to the D30?

Stated another way, if your buddy had a D44 front, I wonder if the R&P still would have went first? Or if the u-joint would more likely to blow first.

Just curious...

[Stu Olson]

I'll have to find out if he was running CTMs or just regular joints. I'm sure the R&P has seen some stress over the past years and that too will take its toll.

[Joe Dillard]

Stu, I think you may know boulderbob (Bob M. from Boulder, CO). He sometimes hangs out on the Colorado4x4 forum. He has been running 37" MT/R's on his ARB equipped LPD30/F8.8 for a while now. I'm not sure if he has upgraded his axle shafts/joints in the front, and I don't recall the diff gears he runs. It's worked well for him and prior to the 37's he ran 35 MT/R's.

Bob is having Chris O install f&r 60's. My guess is that Bob wants to step up things trail wise but wants to upgrade axles along the way.

[TJeeper]

Bob was running Warn inners and outers and CTMs with his 37s. I can't remember if he had 4.56s or 4.88s but I think it was 4.56. He had also re-enforced the axle tube. Part of the reason to upgrade the front to a D60 had to do with the Atlas 5.0 he was having put in.

I have wheeled with Bob a few times, he has an easy right foot, and brings lots of spare parts. I don't think he ever broke an axle with the 37s.

The last time I talked to him, about 4 weeks ago, he was planning on keeping the rear 8.8 and using a wheel adapter to change the bolt pattern. Chris O. would know for sure.

[Joe Dillard]

Originally posted by TJeeper
I have wheeled with Bob a few times

Me too. Next time you see Bob & Monique, tell them I said hi!

[ChrisO]

Yep, Bob had a LP D30, 4.56, ARB, alloy shafts, CTM's and small Warn hub kit. It's sold now.

He still has the F8.8, ARB & I believe the shafts are stock.

I've got the Tera 60R installed with custom long arms (two lower, one upper, & TB), Currie A/R, and it's getting coil-overs (Warn/Black Diamond/Fox). He got a smokin' deal on the axle, shocks & bead-lock wheels from a guy outta Salt Lake City.

I'll be putting spacers/adapters on the F8.8 to match the front width and change the B/C to 5 on 5.5.

I'll post some pics of the suspension when I'm done. The Atlas is in and done and I've posted pics of it here on an earlier thread.

Back on the subject, D30's & 37's. I ran my HPD30 last year with no issues. I've got 4.56 R&P, full Detroit, Warn alloy inners & 30 spline outers (big hub kit), but stock 297's! I'm gonna jump into this season using the same stuff, cause I havent had time to get my new F9" W/CHP built yet.

[sethmark]

Its one thing to throw 37s on an axle and run trail. Its another thing entirely to do front digs with it.

[Iceman]

Originally posted by Stu Olson


I've never been on the trail when someone's D30 R&P went and I rarely see anything posted on the club's BBS concerning it.

A number of rock crawling folks that frequent this board, myself included, use the small Warn hubs as the "intended" fuse....to save the expense of an R&P and possible differential replacement....and my buddy had not gone that route yet.

it happend to me in Moab last year -> LP Dana30 stock with Noslip and 3.73 gears running 35" MT/R's -> the ring and pinion failed before axleshafts -ujoints ....... which was a big surprise to me (it didn't destroy anything else with it though).
Now it sports the Warn conversion (5x5.5, so an oddball compared to the rest due to most wheeling buddies having the 5x5.5 bp) with Warn inners and outers and 297 ujoints, 4.56 gears, still the Noslip and 35" MT/R's -> KOW so far

My buddy runs 37" MT/R's on his CJ stock Dana30 with Lockrite and has had no problems so far
But like mentioned -> it all depends

[TDW]

Originally posted by sethmark
Its one thing to throw 37s on an axle and run trail. Its another thing entirely to do front digs with it.

I do it all the time on the slick stuff up here in the winter. Now climbing up out of Spider and wedged pretty good last summer, front dig was not one of the smartest offroad decisions I have made.