Dana 25/27 Weak Points?

I bought a 53 m38a1 about two years ago and haven’t really had the time or money to mess with it until recently. I put tires on it about a month ago and went with fairly close to stock size I think. They’re 235/86 16s so I’m not worried that I’m running too big of tires, but me and a buddy went out playing in the snow today and got stuck in a drift that I think I could’ve gotten out of if 4wd was working. It has (stock?) full time hubs from what I can tell and the front driveline is turning when I lock it into 4, so something is broken in the front end. Anybody have any idea what it’s most likely to be before I tear into it?

 

The side gears and spider gears inside the diff are usually the first to go, but the axle shafts are a close second.

First, jack up the front end and confirm something is broken. When both tires are up, if you spin one wheel, the other should spin. If the other spins the same direction, it's working and you have a traction-aiding device. If it spins the opposite direction, it's working and you have an open differential. If the other one isn't spinning.... yup. It's busted.

I only ask to confirm because some of these jeeps have such stiff springs, you'd swear something was broken when it's just a tire spinning from a lack of flex.

If something is broken, pull the diff cover first. As you spin a tire, you'll be able to see what is spinning in there and what isn't.

Good luck!

 

That is exactly what I experienced when I got my '63. Tried to go up a hill in a gravel pit on 4wd. Only had one rear tire digging. Neither front tire was spinning. Backed down onto the flat and confirmed hubs were locked in...yep. Had the wife drive it slow while I watched the front drive shaft. Yep...turning. When I opened the front diff both spider gears were smooth as a baby's behind. After a new set of gears it crawled up the same hill, no problem.

 

Always best to check any "new to you" Jeep by pulling the diff covers to check what is there, that both gear sets are the same ratio and that nothing is obviously broken. Either way if the oil is 60 years old it needs changed and the pinion seals needs to be changed on pretty much every old Jeep.

 

I went out and lifted the front end and spun one tire and the other isn’t spinning either direction so I guess it’s something inside. So I guess the next question is would I be better of putting a new set of side gears in it if that’s the problem or just dropping In a lockright? I was thinking I was gonna put an Aussie in the back already but I can’t find an Aussie for a 25 so would I be better off doin lock right front and rear or Aussie in the back lock right in the front?

 

My personal opinion is this: if you have power steering, go with the locker. If not, and/or if you do any street driving in 4wd (snow), keep it open.

 

I’m not planning on driving it much in the winter since it doesn’t have a cab or heater of any sort so maybe driving once or twice a year in 4wd. And it doesn’t have power steering but neither has most anything I’ve ever owned. Throughout high school I drove a Toyota pickup with the v6, 33” tires and no power steering and I survived. How bad will a locker actually affect the steering though?

And I assume they are the full time drive flanges, I don’t see any way to lock them in or anything. When I get a chance I’ll pop the cover off of there and take a closer look. Also to get the carrier and everything out am I going to have to remove any of the steering linkage? It looks like I have enough room to pull the cover off no problem but I’m not sure about anything inside. I’ve never really done anything with any sort of differential before now.

 

Flanges, yes. They are a steel disk that bolts to the hub with a dust cap over the axle end.

 

Yep that’s what I’ve got on there alright.

 

So, what would locking hubs cost me?

 

10 spline hubs are super cheap. Can't hardly give them away these days. $50 tops for a good set of old Warn hubs.

 

I'm a broken record on this but I wouldn't put the money into a 25/27. Other than finding an entire assembly to swap in ( which will be cheaper than a set of hubs and on par with r&r the differential) I'd find a narrow track 30. Beefier, better supported for limited slips/ locker , better brakes and paves the way for a steering conversion down the road.

 

Is a Dana 30 a drop in conversion or what kinda work is gonna be involved?

 

I agree with Rich, but I would cast it like this. A 30 is so much more desirable than a 25/27, that your only reasonable option with a 25/27 is to replace it complete. Daryl can verify this, but I'd expect you can find a replacement axle for near scrap prices. Setting up gears is technical and expensive, so yeah, don't put any money into a 25/27 if you find broken gears. Maybe you'd want to replace axle shafts with used parts ... don't know if it'd be better to fix it or replace it in that case.

No personal experience, but I believe a 30 will bolt in and you'll have to adjust the caster. Doesn't a M38A1 have 5.38s? So you'll have to either make the rear axle match whatever the front axle is (3.73s or 3.54s are common but useless for F134 Jeeps, 4.27 or 4.11 was optional but not common) or regear the front to match the rear. Not cheap or easy.

We are getting ahead of the plot. Take the cover off and look. Look that your gears and axle shafts are ok.

 

It doesn’t have the little 4 banger in it anymore.
The PO put a Buick 225 in and converted it to propane. More than likely I’m not going to be wheeling it hard or anything. Just snow and a little bit of mud. Maybe trailering it down to Moab once or twice a year with some buddies of mine but I’m not planning to do any serious rock crawling in it. I’ve got a 74 scout with a 350/th400 on 35s that I’ll be using for anything real serious. More than anything I just want this Jeep to be something I can take on some light trails around here without worrying about getting stuck.

 

A 30 will require new u bolts, your spring plates will drill out to the larger dia. A new drag link and probably some minor brake line work. Caster you'll have to check once installed, with stock springs you may be OK. You'll have to check ratio on the 27, it may be possible to source a 30 the same or have to regear it.

Like Tim says source another 27 complete otherwise. $100 all day here....