Home » Public Forums » GMCnet » 3.21 fnal drive? and tranny SN
| 3.21 fnal drive? and tranny SN [message #287574] |
Sat, 19 September 2015 19:10  |
skip2
Messages: 544
Registered: September 2011
Location: Winter Haven,FL (center o...
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Couldn't stand it so I pulled the cover off of my final drive and it is clearly marked 1373166-14-45-GM
I counted ring gear teeth and there are 45. So I'm guessing I've got something strange or a little better than stock or both. Something else, the gasket I got from Nick at Applied didn't fit the cover so it went on with RTV. Also does anyone know where the SN is on the tranny? Any input on either subject would be welcome.
Skip Hartline
74 Canyon Lands, FiTech,
3.7 FD LSD, Manny Tranny,
Springfield Distributor,
2001 Chevy Tracker Ragtop Towd
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| Re: 3.21 fnal drive? and tranny SN [message #287577 is a reply to message #287574] |
Sat, 19 September 2015 19:26  |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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skip2 wrote on Sat, 19 September 2015 17:10Couldn't stand it so I pulled the cover off of my final drive and it is clearly marked 1373166-14-45-GM
I counted ring gear teeth and there are 45. So I'm guessing I've got something strange or a little better than stock or both. Something else, the gasket I got from Nick at Applied didn't fit the cover so it went on with RTV. Also does anyone know where the SN is on the tranny? Any input on either subject would be welcome.
Skip Hartline
If you devide the number of teeth on the ring gear by the number of teeth on the pinion gear you will know what the ratio f the gear set is.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: 3.21 fnal drive? and tranny SN [message #287578 is a reply to message #287574] |
Sat, 19 September 2015 19:31 |
LarryInSanDiego
Messages: 336
Registered: September 2006
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IIRC, the '66 and '67 GM E bodies (Toronado and Eldorado) came with a completely different FD and mid axle assembly. The covers are also different from the '68 and later ones.
There's a stamped aluminum tag riveted to the trans slightly above the pan. It has ink printed (possibly unreadable) but also stamped characters. It may say "66 OJ" which means it's a '66 Olds with a specific Toronado application. If the first letter is an A, it likely came from a from an Cadillac Eldorado. I'm not sure what the GMC oem app codes are as I bought mine without a trans and installed a '70 Eldorado trans with FD. Post yours and I'll see if I can find it on the net.
Larry Engelbrecht
San Diego, CA
'73 26' ex-Glacier
TZE063V100319 03/07/73
[Updated on: Sat, 19 September 2015 19:34] Report message to a moderator |
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| Re: 3.21 fnal drive? and tranny SN [message #287596 is a reply to message #287574] |
Sat, 19 September 2015 23:27 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
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The 3.21 has a different number of bolts in the cover. I don't recall how many but it's not the same as any of the other rear ends.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: [GMCnet] 3.21 fnal drive? and tranny SN [message #287609 is a reply to message #287602] |
Sun, 20 September 2015 08:08 |
skip2
Messages: 544
Registered: September 2011
Location: Winter Haven,FL (center o...
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The cover had 8 bolts, So I presume the 3:21 ratio is better than stock but not as good as 3.55. Like how Sears use to sell items "good, better, and best" and this falls in the better. Still geting surprises after four years of the TZE experience.
Skip Hartline
74 Canyon Lands, FiTech,
3.7 FD LSD, Manny Tranny,
Springfield Distributor,
2001 Chevy Tracker Ragtop Towd
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| Re: [GMCnet] 3.21 fnal drive? and tranny SN [message #287612 is a reply to message #287609] |
Sun, 20 September 2015 08:57 |
C Boyd
Messages: 2629
Registered: April 2006
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In my opinion the planetary 3:21 is a "better" differential. I remember when Sears bought Western Auto. A large local WA store had a special sale on Diehard batteries. There were pallets full of batteries in the isles for $49.95. If you walked to the back of the store where the batteries were on the shelf they were normally priced $39.95.
skip2 wrote on Sun, 20 September 2015 09:08The cover had 8 bolts, So I presume the 3:21 ratio is better than stock but not as good as 3.55. Like how Sears use to sell items "good, better, and best" and this falls in the better. Still geting surprises after four years of the TZE experience.
Skip Hartline
C. Boyd
76 Crestmont
East Tennessee
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| Re: [GMCnet] 3.21 fnal drive? and tranny SN [message #287613 is a reply to message #287609] |
Sun, 20 September 2015 08:56 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Skip,
Yep, 8 cover bolts = 3.21 to 1 planetary final drive.
As far as good, better, and best goes that's a matter of opinion. I have heard / read that the 3.21 FD acts a bit like a limited
slip differential, I have no idea if that is correct, however, I have a plan to test that theory next time I'm in the USA.
Also as I understand it GMC had a 3.42 to 1 final drive on the drawing board which was never incorporated as production shut down in
1978.
Double Trouble has a 3.21 to 1 and will run all day long at 70 mph down the freeway and LOVE it. The engine was built by Ken Frey
about 80,000 miles ago, runs 50 psi oil pressure.
I have a switch pitch with a power drive from Manny which I will install eventually and that will result in a 3.66 to 1 final drive
ratio.
Regarding the comments about sealing the cover with RTV and venting; the 3.21 to 1 has a vent hole in the bolt that retains the
drive flange.
http://www.gmcmhphotos.com/photos/fd-visual-differences307-vs-321/p16034.html
Regards,
Rob M.
The Pedantic Mechanic
-----Original Message-----
From: Skip Hartline
The cover had 8 bolts, So I presume the 3:21 ratio is better than stock but not as good as 3.55. Like how Sears use to sell items
"good, better, and best" and this falls in the better. Still geting surprises after four years of the TZE experience.
Skip Hartline
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: 3.21 fnal drive? and tranny SN [message #287651 is a reply to message #287574] |
Sun, 20 September 2015 21:23 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
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Manny did a tranny overhaul at the GMCWS rally today that was chock full of information. One of the things is that a 3.70ish ratio is good. He said that he can get to 3.50 with the power drive (changing the sprockets and chain in the tranny and if someone had a 3.21, that was the cheapest way to get to 3.66. If you had a 3.07, you were cheaper buying a new 3.70 tranny from Applied. Of course, you have to have your tranny out. When I lunched my first Manny tranny by my stupidity, I purchased one of the ones Manny had rebuilt and stored at Ken Hendersons and changed my powerdrive over from the old one to the new one. It's not difficult to install once the tranny is out.
If you decide to go the "I'll just buy a 3.70 diff from Jim K" route, don't throw away the 3.21. It definitely has value that can be used to offset the cost of the new diff.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: [GMCnet] 3.21 fnal drive? and tranny SN [message #287653 is a reply to message #287609] |
Sun, 20 September 2015 21:38 |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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skip2 wrote on Sun, 20 September 2015 06:08The cover had 8 bolts, So I presume the 3:21 ratio is better than stock but not as good as 3.55. Like how Sears use to sell items "good, better, and best" and this falls in the better. Still geting surprises after four years of the TZE experience.
Skip Hartline
Skip,
I don't tow often and have a 455. I have used 2.73, 3.07, 3.21 and 3.55. I love the 3.21 and drive about 63 at about 2500 RPMs and that seems just about right to me. I have been told by smart guys that the 3.21 is a superior design.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: [GMCnet] 3.21 fnal drive? and tranny SN [message #287656 is a reply to message #287653] |
Sun, 20 September 2015 22:05 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
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George,
If you open a 3.07 and a 3.21 side by side you will quickly see why I agree with the smart guys, the 3.21 is much "beefier."
It is also way more complex and probably more expensive to manufacture which is probably why GM only made them for 2 years!
Regards,
Rob M.
The Pedantic Mechanic
-----Original Message-----
From: George Beckman
Skip,
I don't tow often and have a 455. I have used 2.73, 3.07, 3.21 and 3.55. I love the 3.21 and drive about 63 at about 2500 RPMs and
that seems just about right to me. I have been told by smart guys that the 3.21 is a superior design.
George
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] 3.21 fnal drive? and tranny SN [message #287669 is a reply to message #287656] |
Mon, 21 September 2015 06:20 |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
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I replaced my 3.07 with a 3.21 and, according to Miss Garmen, I have no speedometer error. The PO had a speedo correction card that is now not needed. Interesting huh.
Also, getting into our barn can be a problem when it is wet out. It is easy to spin a tire. I can detect no anti-slip effect with the 3.21.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: [GMCnet] 3.21 fnal drive? and tranny SN [message #287776 is a reply to message #287669] |
Tue, 22 September 2015 22:31 |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
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midlf wrote on Mon, 21 September 2015 04:20I replaced my 3.07 with a 3.21 and, according to Miss Garmen, I have no speedometer error. The PO had a speedo correction card that is now not needed. Interesting huh.
The speedometer gear for the 3.21 is unique to the FD and is a metal gear. The others are nylon. So, when the right gear is in the right FD things do come out nicely.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: 3.21 fnal drive? and tranny SN [message #287781 is a reply to message #287772] |
Wed, 23 September 2015 06:05 |
skip2
Messages: 544
Registered: September 2011
Location: Winter Haven,FL (center o...
Karma: 3
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Thanks for the lube level info I was just getting ready to top it off after I found out it needed 4 1/4 pints instead of the 4 pints a normal FD uses. Saves a crawl underneath, I've noticed lately the ground is getting lower and getting upright is getting higher.
Skip Hartline
74 Canyon Lands, FiTech,
3.7 FD LSD, Manny Tranny,
Springfield Distributor,
2001 Chevy Tracker Ragtop Towd
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| Re: [GMCnet] 3.21 fnal drive? and tranny SN [message #287782 is a reply to message #287776] |
Wed, 23 September 2015 06:07 |
skip2
Messages: 544
Registered: September 2011
Location: Winter Haven,FL (center o...
Karma: 3
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I thought the speedo drive gears were in the governer on the tranny.
Skip Hartline
74 Canyon Lands, FiTech,
3.7 FD LSD, Manny Tranny,
Springfield Distributor,
2001 Chevy Tracker Ragtop Towd
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| Re: [GMCnet] 3.21 fnal drive? and tranny SN [message #287792 is a reply to message #287782] |
Wed, 23 September 2015 12:13 |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
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I like to disagree...
I have the 3.70's and love them. I'm very happy I didn't go 3.55 or 3.21, but I never drive 70, 60 is my fave and the 455 loves it there with the 3.70.
I can even drive 55 0r 50 if I have to on hilly roads without downshifting, or opening the secondaries.
If you drive through the Michigan UP, you will agree.
But anything is better than the 3.07
Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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| Re: [GMCnet] 3.21 fnal drive? and tranny SN [message #287807 is a reply to message #287776] |
Wed, 23 September 2015 20:29 |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
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George Beckman wrote on Tue, 22 September 2015 22:31
The speedometer gear for the 3.21 is unique to the FD and is a metal gear. The others are nylon. So, when the right gear is in the right FD things do come out nicely.
I have no idea what speedo gear is in the governor. The governor was off the old transmission, and the FD was converted from a 3.07 to the 3.21.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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