8 1/4 Gear Change Question

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74desertduster

74desertduster

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Have an 8 1/4 with 2.76's in my Duster and would like to go to 3.23 or so.

Have never done a gear change before....I am a mechanic but just never done a rear. Is there a good write up someplace on doing this? Would I be better off buying a complete rear end and swapping it?

Thanks!

Brian
 
well depends on what your doing. if its goin to be a race car just go straight to 8 3/4 or dana. just streetable it will be fine if you dont go too big with the power.now to how easy i assumje you can get the rear appart now can you do pinion depth, gear tooth pattern, bearing preloads and stuff like that its not that bad. you just have to get the rear out cause itll be alot easier. like im doin it now to my 8 1/4 with 3.55 sure-grip. im 17 and everything so far has been easy to me but puttin it back together is another story. my dads friend who is good with mopars and rears is helping me with it.
 
I'm looking into doing the same thing. I want to put a set of gears and a sure grip into my stock 74 rear. It's not going to be a all out drag car, but it will see track time. One tire fires in the burnout box are lame.
 
well my 8 1/4 sure-grip came from summit = $313. pinion bearing and seal,axle bearings and seals, carrier bearings from randy's ring and pinion= $145.3.55 gears out of a jeep = 40. lakewood bfl yellow label gear oil for clutched limited slip rear ends = $27 for two bottles. cover gasket from fel-pro = $8. two spinnin,squealin,smokin tires= priceless. actually not really lol. $533 for a complete rebuild of my 8 1/4 rear with new sure-grip,gears,seals, and bearings. you could probably find some stuff for cheaper but i went all american so i paid a little more.
 
When I went to 3.55 gears in my 8.25 I got a master rebuild kit (all the bearings and seals) and ring/pinion from Randy's. It came with a video that was very good on the basics of rebuilding a rear end and setting up the gears.

I would recommend getting a setup pinion bearing too. It slides on and off the pinion and will allow easy changing of shims to get the pinion depth right.
 
I am going to be doing the same things to my 8.25 within the week, I finally managed to get all the bearings off - long story. I hollowed out the old pinion bearing to use for setup. I have several questions though.

1. Since I failed to pay attention to the direction of the adjusters when I took them out, I'm assuming they go back in with the hex hole toward the outside/ wheel? Also, what's the torque setting for these adjusters?

2. I have 2 sets of 3.55 gears, can I use the pinion off one and the ring gear off the other if they're both Chrysler units, in other words, are they interchangeable?

3. Does anyone have a picture of a known GOOD ink pattern for these rears, esp with 3.55s?
 
1. the hex face out on the carrier bearing adjusters. the adjusters must be turned with a special tool that allows you to reach down the axle tubes. i dont have the torque specs for it at the moment but i can get them

2.no unless your old gears were 3.55's you can not mix gears

3.yes i just have to get it off of my phone it was pefect on the first try with 3.55 gears.
 
what I was saying was that I have two different sets of 3.55 gears, due to extenuating circumstances, I messed up one ring gear, but the pinion in that set looks better than the pinion in the good set, so I was just going to pull a switcheroo.
 
If you mix rings and pinions from different used sets you are guaranteeing that you will have a noisy rear end. Once a set has developed a wear pattern you can't mix the parts without it making noise.

If you are going to go through all the work to rebuild a rear end I would recommend a new ring and pinion, they are that expensive. You can get a set for well under $200 from Randy's or National.
 
I'll just keep the set together, and besides, I'm not sure I want to keep this gear set for very long anyway. If I like it with the OD trans, then I'll put a new set in, IF the old set isn't acting right. Are the adjusters really supposed to be torqued to 100 ft/lbs? Ring gear bolts to 55? caps to 70? I've been doing searches and coming up with different numbers.
 
I dont think so. The adjusters have keepers that are bolted in place to keep em from backing out. Where did you hear that? A good snug fit and then bolt the adjusters in place. No torque value comes to mind. I'll research it though. On your backlash setting it is very minute. I've got to where i dont use the guage all the time. I just do it by feel. Once you've done a few you develope a sence of feel. If i do it for someone else i will guage em but for myself i can feel what i'm looking for. Sort a like petting a fly. A fine sence of feel is required. As far as a tool for the adjusters, i made two of em. I took a rod the right length and welded a hex bolt head on one end and then took an old socket and slipped it over the rod on the other end so the 3/8" drive would be exposed so as to accept a ratchet and they work great. The hex bolt head had to be ground down so as to get a good fit. Good luck and go ahead and dive into it. The bearings are difficult to get off unless you have that set of tools from Randy. Piece of cake if ya have em. As stated earlier, save the old ones and grind the inside out for future mock ups.
Small Block
 
Like I said, I've done a lot of searches online, some on the NAXJA forums, and everyplace has different torque specs. I do know that the adjusters are supposed to be tight enough tro preload the bearings, enough that when you remove the caps, you still have to pry or tap the carrier out. I have already made a tool for the adjusters out of a chev torsion bar and a 1/2 drive socket adapter. $10. You can remove the pinion bearings and carrier bearings with a bearing separator - I know because that's what I used, and I already have the new carrier bearings pressed on, and the old pinion bearing ground out for setup. Funny thing is, out of three pinion bearings I pressed off - 2 were 3.55 pinions and one was the 2.45 pinion - only 1 had a shim, which looks to me to be around .018 - but I dont' have a caliper at the moment. The other two were seated flat against the pinon gear. Now all I need to do is finish setting everything up, and try to get a good pattern, but I also need to know torque specs for everything. My Haynes manuals don't list them. In my searches, I've read everything from 55 lbs to 80 ft/lbs of torque on the ring gear bolts. Does anyone have anything concrete to go by?
 
I've got the diff book from Randys in the shop. I'll go get it and be right back with the info..........Here ya go.
8.25
Pinion preload 12-15 in. lbs. (new)
6-9 in. lbs.(used)
Backlash .006 - .010 inch
Ring gear torque 65 ft lbs
Carrier bearingcap torque 75 ft lbs.
Pinion nut torque crush sleeve

Just for reference the torque on the pinion nut on an 8 3/4 742 case is 240 ft lbs

Make a note when dissassembling the unit where the shims were and how many of what thickness and put em back the way they came out. This will give you a good starting point upon reassembly.

Keep in mind that the ring bolts are probably left handed.
Hope this helps.
Small Block
 
There actually were no shims in it. Which I thought was weird. The only shim I had was in the gear set out of the dakota 8.25. The gear set 70aarcuda sold me had no shims either. Thanks for those torque specs.
 
72BlueSwinger said:
Funny thing is, out of three pinion bearings I pressed off - 2 were 3.55 pinions and one was the 2.45 pinion - only 1 had a shim, which looks to me to be around .018 - but I dont' have a caliper at the moment. The other two were seated flat against the pinon gear.
Click to expand...

When I rebuilt my 8.25 the pinion shim was not between the bearing and the pinion. It was between the race and the carrier. Much easier to set up that way, the race taps out with little effort.
 
I'll check there, then, I haven't gotten the races knocked out yet, which I need to do, but that won't be a problem. Haven't had a chance to work on it with the storms and a 4 month old daughter demanding attention, lol.
 
How easy is it to pull the sure-grip and gears out of a 8 1/4?I have a rear sitting here with new 4.10,s.The rear has 1 broken axel,so I want to pull it apart and sell the center.Any advise will be appreaciated.Thanks.
 
No problem getting the stuff out, Pettyblu. Push the axles in, remove the c-clips from inside the carrier, pull the axles out, remove the caps, and pry out the carrier. You might have to remove the center pin in the carrier to get the c clips out, I can't remember, either way its no biggie. Setting it all back up is the problem.

Alright, so I have a question about these housings. Are there any clearance issues in these 8.25s going from 2.45 open carrier to a 3.55 suregrip? I seem to be getting contact between the suregrip unit and the housing beside the upper right hand cap bolt, where there is a diagonal line coming off the surface of the housing where the cap meets it. It may be because I don't have everything setup right yet, and the carrier is too far over. Wish I had some of you guys around that knew what they were doing. I'll get there sooner or later, though.

Something seems fishy about all this. I hope I have the right suregrip for my rearend. I know it fits the ring gear perfectly. here.. I "borrowed" this pic from pettyblu.. hope ya don't mind.

Picture%20011.jpg
 
I realize what I did now. I bought a suregrip from a dakota 8.25- it looks exactly like the one in the pic above, except the right side shoulder on the carrier is a little squarer - not totally, but there is a difference. The Dakotas have a little larger bearing on the carrier, which provides an additional 1/4 inch of clearance in the spot I drew a circle around. Now I guess I need to clearance my housing just a little bit? Cause there's no way I'm buying another $200 suregrip. If I have to, I'll have the Dakota 8.25 housing cut down to fit under the Dart. I'd really rather just clearance my housing a bit, as it evidently doesn't hurt anything. What do ya'll think?

AND.. should I really have to adjust the carrier over THAT far? I have already added another shim between the pinion and the large pinion bearing, and you can tell the pattern is getting better. So should I buy some more pinon shims, or try to adjust the carrier over some more?
 
my setup was
pinion bearing preload- 26 in. lbs.
carrier bearing caps to- 100 ft. lbs.
solid spacer instead of a crush sleeve .020/.005/.002 shims
backlash .008
and a .070 shim under the pinion bearing cup came like that
i do believe the adjusters are to 75 ft. lbs.
the guy that helped me had a "mopar bible" haynes or somethin and he had all the specs for it but i can see if i can get the specs to put up tomoro

i broke the power cord to my laptop so i cant be on for long waitin for it to come in the mail
 
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