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741 differential.

Russ69Runner

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I have one close to home I am looking at. Is their any difference in the dates they where made. Would you be able to tell if it came out of a Dodge or a Plymouth. Dose it make any difference if it came out of a truck or car. Just asking. Want to get it rite. I was stuck with what came in the car. Don't believe it came in the runner when it was built. Due to it had an automatic transmission in it and it was a four speed car.
 

droptop

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All 69 RR came with a 489 case unless you have the 6 bbl, or those funny holes in your valve covers. Then you got the Dana. All components for a 489 sure grip 8.75 are available.
 

Russ69Runner

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Ran across this.... Frig that! https://www.musclecardiy.com/performance/how-to-rebuild-the-rear-axle/ Nice to know Plymouth made something easy once upon a time.

Can’t answer your last question Russ, never knew enough about them.
Well I watched the or should I say read the article on the clunk problem and all the rest. I was raised by a mechanic in his own rite. His father was a mechanic had his own shop in the depression. Worked on Model A and T's. He showed his son's the in's and out's. My father had a well drilling company and his cousin and he had a machine shop. They rebuilt diesel motor's and gas motor's. Line bored. Put sleeves in the block's. Shaved the block's. Had crank lathes. All types of work on that part of vehicle's. I was their every after noon from school and on the week end's. We never have called a mechanic out to work on our machinery. Like most guy's I have learned by trial and error. Also what I had learned working on my own vehicles. So all in all I should have loaded the axel drive gear's then tried to turn the input on the pinion. After lookin at the spider gear's and axle drive gears seeing no apparent damage to them and with out specks for them figured they where with in tolerance. But so have it they where not so hence you have the clunk. Just to much slack between the gear's. Now I could fix it but you can't get the part for them any more so it is trash. They could be welded up and ground to speck's to get the proper spacing but it is not worth that kind of work. When Racing my buddy and I tore every thing up that you could. Broke pinons off. Broke and twisted drive shaft's. Shattered clutches. Broke 8 blot main's. Twisted axels into. Destroyed bearing's. Destroyed motor's. What can I say. Experience is the best teacher. Book's can only teach you so much. I was told that experience is the best teacher. I have grease and beat up hands from working on car's-truck's and motor cycles. A long with all type's of machinery. So in the end the old story never assume any thing it will bite you in the ASS. Ok enough this novel wont be published. And an Old dog is never to old to learn new trick's. :lol: Russ.
 

69hemibeep

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If memory serves me correct automatics had more lash than a standard that being said less lash will be fine behind an automatic. In fact I don't think Chrysler ever did them differently it was a GM or Ford thing. Ill have to peak at my service manual
 

Russ69Runner

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Bob I have the manual four speed going into the car that is what it came with from the factory. Some one had put this running gear in the car at some latter time. When moving it into the barn I put it into drive and it went clunk. Yes the pinion and ring gear where worn real bad. Looked like butter knives in stead of a gear.
 

69hemibeep

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Personally I would ditch the 741 they were intended for small block A bodies, it might work for you depending on how you drive but why worry. I like the 742 and 489
 

roadrunninMark

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Russ, I think you will be fine with a 741. Remember, any of the old sure grips units will work in any of the modern housings (741,742,489). The ring and pinion are case specific. I am not sure on the the aftermarket stuff but I would assume the same thing. Therefore, if you really want a different to change to a 742 down the line, get another set of gears and bolt to your unit you have in the 741. I plan to run a 741 in Barracuda with a well warmed up 318 (aka junkyard jewel) and 42RH transmission. Unless you have a lot of hp and a 4 speed will you need a Dana.
 

Russ69Runner

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Thanks Bob and roadrunninMark. All info is appreciated. I read that the 742 is rated for at least 500hp with the sure grip. Yes I have the four speed. I would go with the 489 but think that is over kill seeing how I am not racing the car. Just want a driver. Yes the 741 is the lighter differential for a lot less horse power. Once finding out you cant get parts for the darn thing and it being a lighter hp differential will go with a 742. Will have to change up the drive shaft for bigger yoke. Get a way from the miss matched bearing. That way I don't have to order a special bearing. We put a Dana rear end in our street rod and we broke it. So nothing is not hand grenade able. Russ.
 

droptop

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......... I would go with the 489 but think that is over kill seeing how I am not racing the car........


Keep in mind that Chrysler had the most and best engineers of the time (aka the Ramchargers) putting together these cars and they made the standard, not optional rear a 489.
 

Russ69Runner

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Well I am going to make you all happy. I am putting a 489 in the runner. :kartman: now it will take at least a case to put this in. Russ. :steering:
 

Fred69Runner

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Any of the modern 8 3/4 (741,742,489) limited slip units interchange into each other. The gears do not.
Mark, new to this, so if I pull the 741 carrier (non-sure grip) can I install a 489 sure grip and not have to change any other bearings or axles? Thanks for any insite you can provide.
 

droptop

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Mark, new to this, so if I pull the 741 carrier (non-sure grip) can I install a 489 sure grip and not have to change any other bearings or axles? Thanks for any insite you can provide.


You will most likely have to change the drive shaft when changing from 741 to 489. Most 741 use the smaller u joint and the 489 uses the larger one. I have heard of a 2 size u joint but I have no experience with them.

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Fred69Runner

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Thank you for the detailed info. I was thinking I could use the u-joint housing off the 741 and put it on the 489 and not change drive shafts. The u-joint yoke looks like it screws off of the pinion. Thanks again for your hep.
 

roadrunninMark

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Hi Fred, you may have to change the universal joint. As droptop said, it depends if that 489 uses the larger u joint. They do make the 2 sized u joint to make it easy and you dont have to use a different driveshaft then.
 

Russ69Runner

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So it looks like every one else missed saying the 489 has a bigger pinion shaft than the 741 so you need a new yoke on the differential. They make like drop top say's a staggered U joint so you can match to your drive shaft. If needed you can go to a drive shaft shop and have that end changed so you can use the same size bearing through out. That is a better idea but the front bearing will still be small. At some point or another once I do put the 489 in my car will change from transmission to differential all the bearing's to the same size. Doctor Diff. Has a lot of the part's. Good luck my friend. Russ.
 
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