'77 Pacer ring & pinion question
Printed From: TheAMCForum.com
Category: The Garage
Forum Name: Transmission & Drivetrain
Forum Description: If it's between the engine and wheels, it goes here
URL: https://theamcforum.com/forum/forum_posts.asp?TID=101390
Printed Date: Apr/23/2024 at 6:46pm
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Topic: '77 Pacer ring & pinion question
Posted By: Seann
Subject: '77 Pacer ring & pinion question
Date Posted: Aug/12/2019 at 4:47pm
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I'm looking to change the ratio in my Pacer after engine swap. Aftermarket parts suppliers show the Pacer axle as a Dana 35, but this car has tapered axles/separate hubs meaning it could be an AMC rear end, not a Dana. My question is, will Dana 35 parts fit it? I've been told Dana axles have flange shafts...can anyone clear this up? Thanks, Seann
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Replies:
Posted By: Trader
Date Posted: Aug/12/2019 at 6:52pm
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Dana20 or Dana35 parts are not interchangeable with AMC15 or AMC20. That stated, if the cover is round and axles are 2 piece, you have an AMC differential. Now over the years someone could have put a Dana from a Jeep in it or an AMC20. In 1977 the six should have an AMC15 but, being an AMC, an AMC20 may have been put in it right from the factory. As memory serves, Pacer wagons got an AMC20 if the tow package was ordered. That would have to be fact checked! Should add that my 78 Pacer wagon 258 with tow and cold weather packages came with an AMC20. That fact I can verify.
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Posted By: Ken_Parkman
Date Posted: Aug/12/2019 at 10:10pm
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https://en.wikipedia.org/wiki/Dana_35%20" rel="nofollow - https://en.wikipedia.org/wiki/Dana_35
Info from wikipedia says Dana bought the AMC 15 and made it the Dana 35
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Posted By: Trader
Date Posted: Aug/12/2019 at 10:45pm
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Yes the Dana did buy the AMC15 and may be the same in some parts and years. This older thread will get your head spinning: http://theamcforum.com/forum/amc-15-axle-possibilities_topic32248_page1.html" rel="nofollow - http://theamcforum.com/forum/amc-15-axle-possibilities_topic32248_page1.html |
Posted By: farna
Date Posted: Aug/13/2019 at 6:27am
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The ring and pinion from a Dana 35 should fit an AMC 15 with no issues. The axle shafts are different though. Even the non- c-clip axles are a bit different from the AMC 15 axles. AFAIK the differentials are the same as well, but I'm not sure about the spline count or diameter of the axle hole in the spider gears. I think those are the same, but there was an HD axle version of the D35 that had a larger diameter on the hub end (larger bearing and seal). ------------- Frank Swygert |
Posted By: Seann
Date Posted: Aug/13/2019 at 8:41am
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OK, thanks for this info. Next question, how do you tell the difference between an AMC 15 & a 20? Also, if the ring and pinion for a Dana 35 will fit a 15, will it fit a 20? My cover is oval, like the one pictured in Ken's wikipedia link, without the Dana stamp. |
Posted By: Ken_Parkman
Date Posted: Aug/13/2019 at 10:03am
| The 15 (Dana 35) and AMC 20 are completely different. The AMC 20 has a simple round 12 bolt cover, and was used on 8 cyl cars and I believe a lot of bigger cars that did not have leaf springs. |
Posted By: farna
Date Posted: Aug/13/2019 at 5:49pm
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The AMC 15 has a 7.5" ring gear, AMC 20 has an 8.875" ring gear, so no, parts don't interchange. Easy way to tell the difference is the AMC 15 has a fill plug in the back cover, the AMC 20 does not. The fill plug for the AMC 20 is on front to the right of the pinion shaft (right from driver's seat perspective). That AMC 20 cover has 12 bolts and is perfectly round. The AMC 15 cover has 10 bolts and is sort of a flattened circle ("squashed" a bit from top to bottom).
------------- Frank Swygert |
Posted By: Seann
Date Posted: Aug/14/2019 at 9:24am
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OK, thanks...ordering gears from Rock Auto today, will post results, Seann
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Posted By: Seann
Date Posted: Sep/05/2019 at 8:03am
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2:73 to 4:88 gear change for Mazda 13b engine/transmission conversion worked out OK...had to find a diff carrier for the 3:55 and up gears, it's offset to move the ring gear closer to the smaller pinion gear. Also had to use my spider gears. The Pacer is driveable! Thanks for all the tips, Seann
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Posted By: farna
Date Posted: Sep/05/2019 at 8:06am
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This is the first time you mentioned a Mazda 13b rotary engine!! Pics of that install would be real nice... ------------- Frank Swygert |
Posted By: FSJunkie
Date Posted: Sep/06/2019 at 2:41am
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Woah, somebody is building a Pacer the way AMC originally intended to build it: as the rotary engine car of the future with superior performance and fuel economy to other compacts at the time rather than just average on both like Pacers actually were. ------------- 1955 Packard 1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited |
Posted By: farna
Date Posted: Sep/06/2019 at 6:51am
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The only problem is the little 1.3" 13b only puts out 140-160 hp (without turbo... then it's 185-200 with single, 235-280 with dual turbos). The biggest problem with a rotary is they don't make a lot of torque at low rpm. The latest RX-8 engine puts out 238 hp @ 8500 rpm (that's not a typo -- rotaries do like to spin, and that's not redlined!) but only 159 ft/lbs @ 5500. That's why the 4.88 gears were needed. That will get the little rotary spinning enough to make some torque. A five or six speed trans (at least a four speed auto) would be beneficial also. A three speed will be anemic in that heavy Pacer! I think the GM rotary was going to be a bit larger than the little 1.3L Mazda For direct comparisons to a piston engine most sites say multiply the Mazda displacement by 1.5, so it would be more comparable to a 1.95L (2.0L) piston engine. Way too small for a Pacer!!! But it will be an interesting exercise nonetheless, and with the 4.88 gear should be a good around town car. Heck, with the high rpm capability of the rotary it might even be a decent highway car... will be interesting to see the results! A three rotor would be bette, but those are expensive to build. ------------- Frank Swygert |
Posted By: sweatlock
Date Posted: Sep/09/2019 at 2:25pm
Fuel economy is actually quite dismal with rotaries - they’re thirsty little engines. There may now be some technological tricks nowadays to overcome this, but back in the day the fuel economy and emissions were some of the reasons given why GM dropped Wankel development. A modern transmission could help a great deal with fuel economy, along with the aforementioned very low torque output of the design. But there’s a reason why only one car manufacturer decided to soldier on with the Wankel rotary engine design.
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FSJunkie wrote: