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My 1988 Dakota 2wd needs a new rear end.

21K views 54 replies 5 participants last post by  RalphP 
#1 ·
I'm Keith and I own a beautiful(to me) 1988 Dodge Dakota 3.9l 2wd truck that I happen to LOVE. I bought it from a Farmer about two years ago and one trip into Jiffy Lube and the rear end was squealing like crazy. It ended up being my differential bearings. I bought the bearings, but I've been discouraged from taking this task on myself. I can pretty much do anything I learn on Youtube, but I want this truck buried with me, which means I need this job to last. I've been told that it would be easier just to switch out the entire rear end for a different one. My question is, since this rebuild is probably beyond my ability, and the 7 1/4 angular pumpkin diff that's on it seems impossible to find in a salvage yard around these parts, what other rear ends are compatible with my truck that I could get from the salvage yard and get her back on the road? Let's call this a "work truck" restoration. My everyday truck is a 2004 Tacoma Prerunner, but I want this Dodge to live. Any suggestions? Sorry, I'm typing this at work, so pictures yet. I'll add some later. She's ugly, but she's mine.

Thanks for any and all suggestions.
 
#2 ·
1987-1990 Dakota 2WD rear ends bolt right in.

1991-1996 will work, but you'll need to swap the axles and brakes over.

Also, I'd upgrade to a 8.25" rear end while doing (you SURE that's a 7.25" rear end on it?)

To help, here's a quick chart that lets you visually ID the rear ends Chrysler's used through the years:



RwP
 
#5 · (Edited)
That 7 1/4 is definitely mine. I didn't mind the drive before, but if the 8.25 is an improvement somehow, I'll seek that one out. I want a smooth drive. It won't haul anything heavy, I'd just like to get it to cruise on the expressway. Suggestions? Also, I've never swapped out a rear end before. Is there a "how to" somewhere on here, or will my venture at the boneyard be my only practice?
 
#4 · (Edited)
One other consideration for DakotaKeith is that if he picks up a rear end out of the boneyard, he can pick a 8.25; might could find one with a SureGrip unit; and maybe better gearing.

I'd then rebuild THAT one *grins* That way, the truck isn't down all that long while it's being redone.

But the choice will be not only availability but also on his personal preference and ranking of ease / speed / upgrade possibilities / etc.

To DakotaKeith - if you DO pick up a different rear end, check and get the speedometer drive gear out of the transmission also; unless it's the exact same ratio as your current one. I'm finding the Chrysler drive gears to be like $30 or more on line; the local shop up the street from me (PATC) gets about $39 for a gear. A lot pricier just because I forgot to grab one at the boneyard.

RwP
 
#6 ·
The 8.25 is just beefier; some folks buy trucks to haul stuff in, and the 8.25 can take a bit more guff before it decides to become a pile of parts.

It's not a problem with the torque from the 3.9 *grins*, nor with the duty you say you'll be doing with it. The 7.25 is also good'nuff for some folks.

Does your 88 have the 3 speed or the 4 speed auto, or does it have the 5 speed manual?

RwP
 
#8 ·
Here's some pictures of the diff. Now that I look back at it, it doesn't look exactly like any of the Dodge diffs. The trucks a bit of a "frankenstein". Can anyone tell from the photos if it's the 7.25?
 

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#10 ·
I took my last post down and decided instead to do more research. I measured halfway around the ring gear and it came to about 12.5 inches, which is why I thought I had the 8.25 differential, that is, until I found a write up on another forum and found my identical rear end on a different truck. It is, in fact, the 7.25". I think I may have measured beyond half way around the ring gear, accounting for the 25" estimation. I've decided to disassemble it on my workbench and replace the pinion and axle bearings. Attached is a pic of the Motive Gear part #R7 .25r Bearing Kit W/Bearing Incl. F/R Pinion-Carrier-Pilot Bearings/Pinion Gear And Nut/Gear Marking Compound/Crush Sleeve/Brush/Loctite/Gasket-Rtv.

I've seen some very good Youtube videos and I've learned a lot, so my confidence is up. I plan to remove the rear end, install the bearings, replace the brake lines, replace the rear u-joint, treat the surface rust and repaint it. My only concern is reseating bearings without the proper tools, but I'm confident I can either build a jig or use my vice and a large socket to accomplish this.

If there's something that I'm not considering, please make me aware of it. I'm looking forward to learning more about this truck as I restore it.
 

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#11 ·
That's a universal kit, I think - fits more than one rear end.

As long as the gasket matches, it SHOULD be fine.

I'd grab a good rear end rebuild book (I own this one from Amazon: https://smile.amazon.com/gp/product/B00BKRVQUA ) and study it very well before you tackle it.

Since I've not done one (again, I read that book and decided that it was easier to pay someone else instead *grins* but that was my choice), I can't help much past that with actual hands-on.

RwP
 
#13 ·
Well, just as a note, that book I linked to includes the 7.25" diff (front/rear doesn't matter for most of the instructions).

But yah, I've made the same choice due to the tools I'd need. And the space. And it'd be nice to have a garage to work in, instead of not even being a shade tree mechanic (that implies I have a shade tree ... )

RwP
 
#16 ·
i had to do mine on my durango 2 months ago taking it all out is a pain but its fairly easy to put back in. my pinion bearing went then i kept driving it for 7/8 months and it just popped. threw it in 4wd brought it home and it sat for a couple weeks because i lost time but i had to replace everything in the end from it sitting but here are the old gears they have been outside for a little while
 

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#17 ·
Thanks for sharing! I still think this is beyond my ability, but I'm curious. Where did you buy all of the gears and was that more cost effective than replacing the entire differential, OR is this considered a new differential, assembly required? The thing that gives me pause is the possibility of having to use shims.
 
#19 · (Edited)
the only hard part is getting the diff out then back in. then adjust the carrier so the gears meet in the center of eachother and torque down your pinion... thats the only thing i for got to do drove it down the road and it hummed when i let off the gas. had my unlce ream the thing down since he has more weight then me and it has not hummed and is now sporting 33s after i broke in the gears (normal driving for 3/4 days then retorque everything and change oil with normal tires which is recommended )and i never had to use shims but every truck is different. has lasted through trails, red light racing, and small towing. havent thrown a derby car behind it or taken it on a 2 hr drive yet to really test it
 
#24 ·
The hardest part usually is properly setting the crush sleeve.

Here's a replacement part:

http://www.ratechmfg.com/chryslerspbs.htm

I'm going to keep looking; there's a reusable crush sleeve replacement for the Ford 8.8, I can't see why they don't make one for the Chrysler 8.25 / 7.25 .

But be DARN sure to measure when you take it apart - I'm not going to swear to it, but I'd bet that's actually a 8.25" rear end from the shape.

RwP
 
#26 ·
Okay, so I've come into an 8.25" rear axle assembly, 3.54 ratio(which means it's a dana, right?) for a steal. The question is, I'm buying it from a guy who has the 4wd version of my '88 Dakota. Could there be a compatibility issue? If not, I can swap this one out for mine and take my time rebuilding mine in the meantime.

Any thoughts?
 
#28 ·
The 4x4 axle for a 1988 factory isn't a Dana; that's different.

(None of the factory ones for the 1988 trucks are Dana's.)

The 4x4, if it's from a 1st Gen, will be under the leafs; your 4x2 axle is over the leafs; it will raise the back of the truck a bit.

If the truck is a 1st gen it's coming from, try to get the speedo drive gear out of the transmission also! That's a good $30 or more on the open market, and is required to get the speedo working right.

RwP
 
#30 · (Edited)
3.54 and 3.55 are essentially identical - it just depends on whether the manufacturer rounded up or down during the calculation. It's possible to have a 3.54 front and a 3.55 rear from the factory.

The Dana 44 has an 8½" ring, Dana 60 has a 9¾" ring. 8¼" is a Corporate rear.

The Dana covers are 10 bolt and look like a poorly drawn stop sign. The 8¼" has a 10 bolt oval cover.
 
#31 · (Edited)
So this "great deal" was for a Chrysler 8.25 rear end 3.54 ratio with opposing shock perches. One facing forward and one facing rearward. It's from a Jeep XJ.

(Query: What exactly does opposing shocks help anyway?)

Unless I figure out how to move one perch or replace them both, I'm still without a rear end. Is there some third party solution that will enable me to use this rear end or should I just buy it and sell it to a Jeep Owner for more money? This is becoming quite an education for me.
 
#33 · (Edited)
Yeah, mine are not opposite. My truck is first generation 1988.

I'm wondering if it would be easier just to weld an upper shock mount in the appropriate place to receive the forward shock instead of moving the forward axle mount to the rear. I'm not going to be off-roading in my truck, so that might be the better solution. Anyone with any experience along these lines, please chime in.
 
#34 · (Edited)
Okay, so here I am.
I had to cut one of the rear leaf spring bolts off, but I'll replace that and the insert.


The rear axle with diff lid off is what came out of my truck. The other, a Chrysler 8.25" 3.54 ratio rear axle assembly out of a Jeep XJ is what's going in. I've pretty much decided to relocate the upper shock mount to accommodate this new rear end with the opposing mount.

I'm about to clean it up and install it, but I'm not sure where the inbound brake line goes. Does it attach onto what looks like a bleeder tip on the right of the brake line junction in the "New Close up" pic or is that the axle vent? I assume it's either that bleeder thing or the center hose. I cut my previous one because I couldn't figure out how to get it off of the axle.

Also, what should I clean this rear end with? Just mild detergent or should I hit the entire thing with brake parts cleaner or is that a bad idea?

Sorry for so many questions, but as much as I'm enjoying this learning process, and I am immensely, I'm still a complete Rookie.
 

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#36 ·
That white plastic thing is probably supposed to be a vent; on my 1988, the T-block is held in place by the axle/diff vent tube (which just has some rubber hose up into the frame to let it vent any fumes out.)

You realize you're going to raise the rear end quite a bit (about 3" IIRC) with the spring seats on the top, right?

RwP
 
#37 · (Edited)
Actually, I was told it's going to lift it about 5 inches, which would be weird so high in the back, so I'm installing a flip kit. Any suggestions? I can't seem to find one specifically for my Dakota. Should I get a kit for XJ because of the axle?

Oh, and does that plastic thing need a hose?
 
#39 ·
Lol, there's no shop. I'm doing the work myself. I'm not going to cut the perches off and modify the rear end. That way if this doesn't work, I can sell it in it's original form. There are some universal flip kits. I assume one of those will do as long as the U bolts fit around my axle.

Oh, and the brake line with the tee is part #V1128096AA . I'm ordering that to complete this job.
 
#40 ·
*frowns*

I'd ask someone who's used a flip kit ... I'd rather have secure spring perches welded to the axle tubes personally.

That said - the flip kit for the Jeep XJ would be what I'd look for, since the flip kit needs to fit the axle.

Of course, you've checked that the out to out on the axle is the same, and that the center to center on the spring perches are the same, right?

Most of the flip kit may not be needed - the shackles and mounts for your current springs, for instance, should still work fine.

RwP
 
#41 ·
Got the rear axle assembly installed. Man, do I hate the stance of the truck with the Jeep rear end in. It is so adolescent. It doesn't matter anyway because I didn't properly measure so the drive shaft is about 1/2 inch short, lol. I can take a hint. Back to replacing the bearings in the original.

So what's the trick to getting the pin out? I've tried WD40, tapping the back side with a socket. What else can I try?

Having a ball, btw. I hope the lurkers are at the very least entertained.
 
#42 ·
So what's the trick to getting the pinion shaft out? I've tried WD40, tapping the back side with a socket. What else can I try?

Having a ball, btw. I hope the lurkers are at the very least entertained.
Problem solved on the 7.25" rear axle. The pinion shaft lock bolt was actually broken off inside. Since I can't drill it out because of the angle of the socket, I'm going to drill out the pinion shaft until I reach the broken piece of the bolt and replace both, that is if I decide to continue. The only real reason I'm attempting this is because I've had the bearings for some time now and if I can rebuild this rear end, I'm back on the road. Before I damage something I will enlist the help of a local shop to complete this job. The XJ rear axle assembly will be for sale on Craigslist by Wednesday morning.

1987-1990 Dakota 2WD rear ends bolt right in.

1991-1996 will work, but you'll need to swap the axles and brakes over.

Also, I'd upgrade to a 8.25" rear end while doing (you SURE that's a 7.25" rear end on it?)

To help, here's a quick chart that lets you visually ID the rear ends Chrysler's used through the years:



RwP
This post was the best advice I got in this thread and I should have listened. I had a bad case of "Youtube" courage, thinking that this stuff is as easy as it looks in a video. Man was I wrong. If the rebuild costs more than a direct match rear axle swap, I will be purchasing the correct real axle.

So I've come full circle and I know this truth to be self evident; I'm no Mechanic...I'm a check writer.
 
#43 ·
...and she's back on the road.

I found a 1989 Dakota in a salvage yard, pulled the rear end and performed the exact match swap without complication. Thanks, Ralph P for your original advice!

It's definitely an 8.25", but that's all I know so far. It must be a higher ratio, because the truck now has some get up and go. When I accelerate from a stop, I burn a little rubber now, which is cool. It's a limited slip or locking differential because, unlike my original diff, both wheels rotate in the same direction while on jack stands. I'm going to Google the serial number on the pumpkin to find out specifically what the ratio is.

I'm actually going back to get the tailgate, rear bumper and even the bed liner off of the same salvage truck. I would even consider changing out the dashboard components because my 88 offers very little monitoring information. Glad to have her back on the road.

I still have the Jeep rear end for sale on Craigslist...
 
#44 ·
A few more suggestions:

1) Grab the speedo gear out of the transmission, and swap that into your truck. That will help keep the speedometer a bit more accurate.

2) There should be a tag on the rear end - mine has 2 9 on it (for 2.94, open).

3) Grab as much of the dash wiring harness as possible, and a copy of the 1989 FSM so you can verify the wiring is OK. You'll have to add the proper temp and oil pressure sensors to the motor to use the gauges, alas.

RwP
 
#45 ·
How complicated is replacing the speedo gear? Not being a Mechanic, and having wasted so much time already, I'm a bit intimidated. My speedometer is currently showing 55mph when I'm doing about 30mph, so I understand how important this is. I'm going to leave changing out the front panel for a later date.
 
#46 ·
Well, it's a single bolt (about 3/8" IIRC) to release the fork, release the VSS from the housing, and twist and remove.

Also, pay some attention - there's four ways it fits in, only one fits properly for that gear, and it should be in that way. I.E., note what numbers are at the bottom (that's the speedometer gear tooth range for that position).

If you can, I'd also grab the VSS ... them things are pricey when you have to buy one!

To replace, just put the gear back into the plug you remove, ease it in turned the right way, and the fingers on the holddown will line up with two of the notches when it's turned the right way. Put the holddown back down, tighten the bolt, reattach the VSS, and you're golden.

That reminds me ... I've got to swap mine, I got new tires that are a bit bigger so my speedo (which was spang on with 215/75R15s) is a bit off (due to having 235/75R15's on).

(Also I'm getting intermittent VSS failures, code 15, so I'm replacing that also. Le sigh. Another $100 down the drain ... )

RwP
 
#47 ·
Great! I can handle that.

I'm wondering about the bed liner and tail gate now because I was comparing my '88 with the salvage yard '89 and they are different widths. According to Wikipedia, the '89 is about 1 1/3 inches wider. I'm going to measure my truck and compare the measurements with the '89 so that I'm not stuck with a bed liner or tailgate that won't fit.

I've never noticed this before, probably because I've been driving my Toyota every day for months, but the Dakota is a noisy ride. It sounds like snap pops when I drive over gravel, even at a speed of 20mph. The sound is up front. I think it might be the new transmission oil pan. How can I dampen this sound? Any ideas?
 
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