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8 3/4 diff interchange
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59 in Calif
Posted 2018-12-25 1:48 PM (#575798)
Subject: 8 3/4 diff interchange


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Posts: 1096
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Location: Hayward, Calif
Hey Guys, This is a bit non FLK, but will my 8 3/4 diff from my 69 D100 interchange into a 2000 Dodge 1500 truck. My D100 is pretty much wore out, but has a good limited slip diff and I would like to put it in that 2000 Dodge truck. If it is just a matter of R & R. Thanks, Jerry
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Shep
Posted 2018-12-25 2:39 PM (#575799 - in reply to #575798)
Subject: Re: 8 3/4 diff interchange



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Posts: 3114
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Location: Chestertown, NY ( near Lake George)
Does that truck have an 8/34 rear now? Or do mean replacing the axle housing?
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59 in Calif
Posted 2018-12-25 3:22 PM (#575801 - in reply to #575798)
Subject: Re: 8 3/4 diff interchange


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Location: Hayward, Calif
Shep, I don't know what diff it has, as I haven't bought it yet. I am trying to get some info beforehand. I don't intend to swap out the whole rear axel, hopefully just the diff. I'l call Napa tomorrow and see if both trucks use the same mounting gasket. That might be my first clue. There is a gear shop here in town, I'l go talk to him also. Just thought maybe someone on this forum may have some knowledge about this. Thanks, Jerry
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57chizler
Posted 2018-12-25 3:30 PM (#575802 - in reply to #575798)
Subject: RE: 8 3/4 diff interchange



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Posts: 3166
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Location: NorCal
Your '00 1500 probably has a 9 1/4" rear end; your tape measure will tell you if the spring centers are the same. If they are, the other likely differences are the U-joint (adapter joints are available) and the driveshaft length; the 9 1/4" driveshaft will be a little (about 5/8") too long for the 8 3/4" rear end.
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59 in Calif
Posted 2018-12-25 5:36 PM (#575806 - in reply to #575798)
Subject: Re: 8 3/4 diff interchange


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Posts: 1096
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Location: Hayward, Calif
I did some checking around and the answer is NO. The 2000 Dodge diff gears load thru the back side of the axel housing after removing that cover plate. Seems the only option is to get a limited slip unit and have the existing ring gear mounted to it. Summit has them for about $500. Well, it seemed like a good thought at the time. Jerry
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58coupe
Posted 2018-12-25 8:00 PM (#575811 - in reply to #575798)
Subject: Re: 8 3/4 diff interchange



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Posts: 1370
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Location: Alaska
I believe Mopar stopped using the 8 3/4" around 1974 or 75 and started using the 8 1/4" and the 9 1/4" diffs. that are not removable like the older one. If you want to save a little money, there should be plenty of the 9 1/4" diffs. used and with limited slip.
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CrAzYMoPaRGuY
Posted 2019-02-12 10:13 PM (#578124 - in reply to #575798)
Subject: Re: 8 3/4 diff interchange


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Location: Locked in my Canadian garage....
There are tons of limited slip 2000 Ram rears in the wreckers. Cheap!!!
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58coupe
Posted 2019-02-13 11:48 AM (#578147 - in reply to #575798)
Subject: Re: 8 3/4 diff interchange



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Location: Alaska
The problem with using the newer Ram diff. is their bolt pattern. I believe they are 5 on 5 1/2" and of course the spring pads have to be changed. Not sure if the width is close to a FWLK.
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CrAzYMoPaRGuY
Posted 2019-02-13 5:59 PM (#578177 - in reply to #578147)
Subject: Re: 8 3/4 diff interchange


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Location: Locked in my Canadian garage....
58coupe - 2019-02-13 11:48 AM

The problem with using the newer Ram diff. is their bolt pattern. I believe they are 5 on 5 1/2" and of course the spring pads have to be changed. Not sure if the width is close to a FWLK.


He wants the rear for a 2000 Dodge truck no?? Not a Forward Look...... unless I read it wrong..?
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58coupe
Posted 2019-02-14 11:13 AM (#578205 - in reply to #575798)
Subject: Re: 8 3/4 diff interchange



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Location: Alaska
I owned a 72 Dodge 1/2 ton and it had the 8 3/4 rear with 5 x 4 1/2 wheel bolt pattern which is different from the newer Rams. It may fit but you would have to use 2 different wheel sizes.
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59 in Calif
Posted 2019-02-16 11:22 AM (#578289 - in reply to #575798)
Subject: Re: 8 3/4 diff interchange


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Posts: 1096
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Location: Hayward, Calif
Hey Guys, Let me clear this up a bit. I was just looking to see if the 8 3/4 diff (ring & pinion & limited slip ) from my 69 D100 would fit into the axel housing on my 97 dodge Ram. The axel housings are completely different and NO interchange is possible. I have no intention of swapping out complete axel housings. Plan to scout out the local junk yards and find a limited slip unit ( not the whole axel ass'y, just the limited slip unit) from a newer generation rear end. Sorry for all the confusion. thanks, Jerry
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57chizler
Posted 2019-02-16 12:53 PM (#578290 - in reply to #578289)
Subject: Re: 8 3/4 diff interchange



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Posts: 3166
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Location: NorCal
The confusion is understandable, some people call the complete rear end assembly the "rear differential".
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Powerflite
Posted 2019-02-16 3:23 PM (#578301 - in reply to #575798)
Subject: Re: 8 3/4 diff interchange



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Location: So. California
Generally, the center unit by itself with the spider gears in it is called the differential (open or sure grip), the pull-out unit with gears & differential on an 8 3/4 or 8", 9" Ford is either called a pig, gears, or gear assembly. Gears by themselves are called a gear set. The axle housing is just the housing. The axle is just an axle, and the whole thing is called a rear end or rear axle assembly. It's already confusing without even bringing up tall vs. short gears etc. which can be even more confusing.
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58coupe
Posted 2019-02-17 11:07 AM (#578328 - in reply to #575798)
Subject: Re: 8 3/4 diff interchange



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Location: Alaska
Jerry, thanks for clearing up all the confusion. FYI I am pretty certain you have the 9 1/4" in your 2000 truck and Chrysler started using these from the late 70s on. There should be plenty of these available used. You will need to buy or make a special tool to remove/adjust the side nuts on the carrier ( I made mine). It needs to be about 3' long or so and reach in from the ends of the axle tube.

Edited by 58coupe 2019-02-17 11:12 AM
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57chizler
Posted 2019-02-17 6:20 PM (#578342 - in reply to #578328)
Subject: Re: 8 3/4 diff interchange



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Posts: 3166
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Location: NorCal
Some people claim that the hex end of a torsion bar will work to adjust the side nuts. Never tried it.
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58coupe
Posted 2019-02-18 11:38 AM (#578366 - in reply to #575798)
Subject: Re: 8 3/4 diff interchange



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Posts: 1370
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Location: Alaska
Don't know about a torsion bar. I used a large metric hex nut that measured about 35mm across the flats , welded it to a tube and welded a 1/2" socket to the other end.
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