8 3/4 gear swap

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Jul 31, 2008 | 02:44 PM

mopar_go_car

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8 3/4 gear swap

I have an 8 3/4 (741) casting with 3.23 gears. This setup is currently in my 74 plymouth valiant with a built 318/360 heads etc. (nothing too radical) My question is what do i need to do for a simple gear swap. (For adjusting the depth etc.) I have a set of 3.91 i would like to put in it. I know my 741 is the weakest of the 3 housings but it will have to work for now. I bought an installation kit from Richmond Gear and I can take it all apart but its getting the new one set up right i need some assistance with.

thanks

rick

Jul 31, 2008 | 11:35 PM

Doc

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Are you sure the new gear set is a 741 style ?

Aug 1, 2008 | 10:28 PM

chlngr1970

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Good topic. I will be replacing my gears in my Duster soon, and have the same questions. Is an 8.75 housing universal, in that you can change from a '741 to a '742/'489 housing? I guess my other option is to just pick up a new hosing from Mncini Racing

Aug 1, 2008 | 10:48 PM

Doc

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ALL those housings are diff ... the most popular of the 3 is the 742. And the 742 has also the largest selection of ratios .. the last time I checked.

Aug 2, 2008 | 08:58 AM

mopar_go_car

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My housing is a 742 (midgrade i guess) and i ordered from summit a
rmg-6903751 ring and pinion set. (3.91) and a
rmg-831037-B (half installation)which has the following

Brand:Richmond GearProduct Line:Richmond Gear Installation KitsPart Type:Ring and Pinion Gear Installation KitsPart Number:RMG-831037BCover Bolts:10Ring Gear Bolts:12Pinion Spline Count:10Ring Gear Rotation:StandardCover Gasket Included:YesPinion Shims Included:YesCarrier Shims Included:NoCrush Sleeve Included:YesPinion Seal Included:YesPinion Nut Included:NoRing Gear Bolts Included:NoHead Bearing Included:NoTail Bearing Included:NoCarrier Bearings Included:NoAxle Seals Included:NoAxle Bearings Included:NoQuantity:Sold as a kit.

Aug 2, 2008 | 11:30 AM

Doc

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So you have both the 741 and 742 housings ?

Aug 2, 2008 | 04:52 PM

chlngr1970

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Quote:

Originally Posted by Doc

ALL those housings are diff ... the most popular of the 3 is the 742. And the 742 has also the largest selection of ratios .. the last time I checked.

Sorry to go off topic, but does this mean that I can't put a 742, or a 489 case in my 8 3/4 housing?

j

Aug 3, 2008 | 12:34 AM

Doc

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??? ... people label things different. If what you are calling a HOUSING the part that the axles are in ?

Aug 3, 2008 | 02:39 AM

chlngr1970

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Well, I have an 8 3/4 Rear End Housing

that has a 741 third member

Will a 742/489 third member fit in any 8 3/4 housing?

Does that make more sence?

j

Last edited by chlngr1970; Aug 3, 2008 at 02:55 AM.

Aug 3, 2008 | 10:58 AM

#10

Doc

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Yes ! ...

Aug 3, 2008 | 12:37 PM

#11

chlngr1970

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Great!

It's good to know we are on the same page.

Back to the origional question, If you can make sure all your cllearences are good, then you should be set. If you are not good at rear gear setup, get to an expert...they can save a lot of heartache.

I'm on the lookout for a good grear man here in NW Washington.

j

Aug 3, 2008 | 07:33 PM

#12

Doc

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Housing, case, third member .. !! .... I have heard people refer to all three differently. It is kind of like the way people label rear end GEARS ....

Some say a 2.76 gear is a SHORT gear .... or a TALL gear.

I say it is a SHORT gear.

Aug 4, 2008 | 02:13 PM

#13

mopar_go_car

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I was wrong in my initial post. Thought i had a 741 BUT I actually have a 742 currently in my car with 3.23 gears. Have the 3.91's new in box and im thinking i need the tool to know (adjust) the depth on the new ring and pinion.

Aug 4, 2008 | 10:13 PM

#14

chlngr1970

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Yeah, the 742 is the better of the two, congrats. I need to get under my truck to see what it is. Been a long time, but IIRC, it is a feeler gage, like a key ring of different thicknesses of metal, starting at like .005" thick and going to say, .1" thick...

Wow...I didn't think I was that out of it. I found out yesterday that one of my past gurus that I would trust on all things MOPAR passed away, and I find out about it almost 5 months later. Moving half a country away realy takes you out of a scene