Hello, new member here. Not new to Dodge trucks though. I've searched in the forums and haven't found another post that covers this so if I missed it....sorry. I was hoping someone has done this and can give a quick answer. I have an 86 D150 Royal SE, that has an 8-1/4 rear axle with 2.94 gears. It has the 318 with lockup 904 transmission. I want to swap to 3:55 gears. I found a clean 9-1/4" rear end in a 95 B1500 in the salvage yard that has 3:55 gears and sure-grip. I didn't have a tape measure with me so I couldn't get dimensions today. Can anyone tell me if the rear axle width is the same as the D150? It has the same 5.5" bolt pattern on the wheels with 15" tires and doesn't have the different offset like the 2nd gen trucks have. Lastly, will I have to shorten the driveshaft if the rest of the dimensions are the same?

The salvage yard also has a 92 dakota with an 8-1/4 and 3.55 gears. The ring and pinion should interchange so I can go that route if the van rear won't fit. I would like to upgrade to the heavier duty 9-1/4 for towing and more power later down the road if anyone's curious. I also grabbed the lower control arms from the van as I plan on lowering the truck front and rear.

 

Well I went back to the junkyard today to check the rear axle in the van. I brought the tape measure with me today. Here's the dimensions on a 95 B1500 9-1/4" axle. Axle flange to flange without the drums measures 66". Leaf spring center to center is 49". The 8-1/4 in my truck is 43-1/3". The distance from the center of the u-joint on the pinion yoke to the center of the axle is about 12". That one is kinda hard to measure accurately. Inside to inside of the backing plate mounting flange is about 60". It's hard to measure accurately with a tape measure and the rear cover on this too. The 8-1/4 in my truck measured 59" at this point.

From what I checked it's the right width, bolt pattern is the same and the pinion yoke to the center of the axle is the same so I won't have to shorten the drive shaft. Here's the things that will need modified to make it work:
1. Will have to cut off the spring perches and move in about 3" on each side. This is going to put the edge of perch right on the edge of the step down in the axle tube.
2. The b-van axle has shock mounts welded to the axle tube on the front side of the axle. They are set up just like a 2nd gen dodge truck and use a bolt through the lower shock instead of a stud with a smooth shoulder like the first gen trucks.
3. The brake line and vent are on the passenger side. First gen trucks are on the driver's side.
4. There is an ABS sensor on the differential. Older first gen trucks won't need this.

I went ahead and bought it. It cost $135 with the drums. The oil looks like new. There was no rust on it. The van was a fleet model so It looks like it was well maintained during it's life. I can make the few changes necessary to make it work in my truck. I just wanted to post all of this in case someone else wanted the info.

 

I forgot to mention in the last post that the the U-bolts and plate that hold the axle to the springs in the B1500 will work for an axle flip lowering kit. It has the rounded u-bolts that go over the axle tube instead of the squared off u-bolts that go over the leaf spring like the D150. The u-bolt plate that goes under the axle on the D150 won't work well for an axle flip. I think the plate from a car would work better for an axle flip because it has the shock mount built into it. The van plate doesn't have a shock mount on it, it's just a rectangular plate with 5 holes in it. I'll have to research that a little more before I make up my mind though.

 

You should be able to find the right rear end, 78(ish) to 93 D100-150 will bolt into your truck/ though if you get one from an 84 or earlier you will need to put your axle shafts into the replacement housing and use your drums, because of bolt pattern difference for wheels.
have done this before.... this is assuming your replacement is also an 8-1/4. If the replacement has 10" brakes and yours is 11, easy to swap backing plates between axles.
Again I have to ask Why oh why do so many people want to LOWER these trucks (as I shake my head)

 

Unfortunately finding a good 9-1/4" rear from an 85-93 Dodge 1/2 ton pickup in my area is nearly impossible. If I found an 84 and older model that had a good rear axle, I would still need to find and 85-93 model to rob the large BP axles out of. Over the past 25 years of junkyard scrounging that I've done, I rarely if ever find a 9-1/4" rear in a 2wd version. I estimate 90 % of the 2wd models I've seen have the 8-1/4" rear. I had a 79 D150 back in the 90's that had the 9-1/4 rear, but it was a Warlock with a factory 360. I also had an 87 D150 with a slant 6, OD 4 speed and 3:91 8-1/4 rear. It's also been rare to see a 360 from the factory in a 93 and older d100 or d150. Of the few d100's and 150's that had the 9-1/4" rear, all of them had a 360 or big block engine.
I've found that most of the 4wd 1/2 ton models have the 9-1/4" in them, but rarely have the 3:55 gears in them. Nearly all I run across have 3:23 gears. Every one I've found recently from a 4wd is either rusted too badly, has 3:23 gears, has been underwater and is full of mud and water, is attached to a complete parts truck, or is still in someone's running truck that they want too much for(for my budget).
This is why I'm trying to make this rear work in my truck.
As to the reason why I would want to lower this truck....why not? I've had many Dodge trucks in my life. This 86, the 87 slant 6 one, an 85 royal SE D150 shortbed that I put a 360 in(I sold it to a guy in SW Missouri around 2000, I wonder whatever happened to it, new black paint, red interior, every option available?), The 79 D150 stepside, 89 Ramcharger 4WD and a 71 D100. My Dad owned a 66 D100, a 76 D200 and an 84 D100. They were all stock except for the 360 swap in the 85 royal SE. They were all used as a truck was intended. This one isn't. I guess I'm tired of driving stock looking trucks at this point in my life. Now that it's running and driving good it's not worth much. There's still plenty of nice examples like this around. It's not rare or collectible($$$ collectible). This truck was going to be a donor for body parts for a first gen cummins project. The guy I got it from bought it, then decided he wanted to go a different direction and didn't use it. He was going to sell it for parts since it didn't run well and had no brakes. I paid $500 for it and got the brakes fixed and engine fixed(had a flat cam lobe, first one I've ever seen on a 318) and it's a decent rust free low mileage truck. When I lower it, I won't be doing anything that can't be undone easily by myself or someone else down the road. If I didn't lower it, I would sell it and someone else would just run it into the ground using like a truck or part it out to fix the rusted out body on their first gen cummins. So in my opinion, the best chance for this truck to stick around is to lower it. If I don't like it I'll put it back to stock.

BTW, is this the same VolareDon that's on the Slantsix.org site?

 

yeah that's me.
I don't get how lowered/not lowered would determine whether a truck sticks around. You sound like me I've had a few of those trucks, and still prefer those to a new one. I got my85 almost a year ago, been looking. I wish they were still as all over around here as by you. They are a tough find in any sort of decent shape around here. I'm always looking on CL in the south that I can't seem to get out of illinois to do anything about, but even at that they have become slim pickens

 

I see this thread is almost a year old. I need a rear for my 86 which is a 8.25" with 3.55 gears. I found one that someone picked up for their 72 D series. The say it has the 5.5 lug circle but I need to make sure the spring spacing will be correct before driving 4 hours to see it. Is the spring spacing the same for a 72 d100 and the 86 D150? They use the same u joint at the rear so I should be good there. I can always swap axles if the pattern is wrong as it was the pinion bearing that grenaded in my old rear. To think a bearing failure at 515000 miles, what has happened to quality control??

 

72 is probably 5 on 4.5" bolt pattern.

 

The person that ha sit said it is a 5 on 5.5 so it should work there. He purchased it for a 72 and it was supposed to fit. Not sure why they are selling but it never got put in. I just need to confirm that the spring spacing is correct for the 86 before driving 4 hours to get something that might not Fit.

 

Ive put an 8-3/4 from a 69 into a 79, bolted right in. But it was 5 on 4-1/2 just like the original rear that was in the 79. never seen that early of a Dodge truck with 5 on 5-1/2. The housing from the 72 will bolt right into your 86, though the brakes are probably narrower 2" instead of the 2-1/2 wide shoes on an 86. Just buy all rear brake components for the 72 and you'll be good there. IF in fact the bolt circle is right/
you can always get rotors from an 84-older and make teh fronts 5 on 4-1/2 so you can put matching wheels on and not have to carry 2 spares.
4wd went to a 5 on 5-1/2 starting with part time 4wd models in 79 or 80. otherwise if full time 4wd they were still 5 on 4-1/2