Rear-End Identification help - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Tx70Gmc · 01-14-2022, 01:17 PM

Can anyone help identify my rear-end?

I posted a reply in a very old thread, but did not have any luck getting responses, so I figured I would try to post a new thread.

I have searched the forums and came across a post that referred to some identifying factors, but I'm not sure what it all means.

here is the post:
http://67-72chevytrucks.com/vboard/s...79#post9018479

Can you help me identify mine?

67890 - GM 12 bolt
E120 - May 12, 1970
NF3896838

Axle Stamp = TDA 0521W1

so I think the TDA means its a 3.73 gear and I think the 052 is the 52 day of the year it was built? and I have no clue what the 1W1 means?

any ideas?

Thanks,

**MikeB** · 01-14-2022, 06:00 PM

Yes, TDA on a 1970 rear end means 3.73 gears. Funny, but on 1971 models TDA means a G30 van with 4.57 gears.

I didn't spend a lot of time searching, but can't find anything on 0521W1.

**Getter-Done** · 01-14-2022, 06:40 PM

I did not find the 0521M1 either.

I did find this in the link below.

Link: https://www.chevyhardcore.com/tech-s...rearend-guide/

Tx70Gmc · 01-14-2022, 06:57 PM

I read that entire article and it helped with date code, etc but not the 0521W1

**Getter-Done** · 01-14-2022, 07:08 PM

Quote:

Originally Posted by Tx70Gmc

I read that entire article and it helped with date code, etc but not the 0521W1

Yeah

There is lots of info for cars.
I tried using different search words to dig a little deeper for truck stuff

Maybe someone will know the answer

BigBird05 · 01-14-2022, 10:19 PM

Mike B 71 is a different axle than a 70.

BigBird05 · 01-14-2022, 10:48 PM

I am looking at it a different way. 0521 is May 21st day, W is the plant that assembled the axle, 1 is first shift.

Tx70Gmc · 01-15-2022, 12:01 AM

Quote:

Originally Posted by BigBird05

I am looking at it a different way. 0521 is May 21st day, W is the plant that assembled the axle, 1 is first shift.

Maybe your on to something.
The pumpkin has the code E120, which was May 12,1970
And maybe the axle was made on May 21, 1970?

Would that make sense?

**MikeB** · 01-15-2022, 05:32 AM

Quote:

Originally Posted by BigBird05

Mike B 71 is a different axle than a 70.

How so?

BigBird05 · 01-15-2022, 06:59 AM

Quote:

Originally Posted by MikeB

How so?

Tx70Gmc, The pumpkin code is cast into it, the axle code is stamped.

Mike B 70 and 71 axles are a different width. I think the 71 is wider by maybe an 1 inch.

**uncle** · 01-15-2022, 10:58 AM

Is the rear axle a five or six lug. What year is your truck? About 95% of the 70 model trucks that I’ve had had the same width housing as 71 and 72. I’m not saying they all do but most that I’ve experienced have.

**uncle** · 01-15-2022, 11:02 AM

I probably didn’t read all the above post very carefully but here’s a post from a board member years ago as far as the code and gear ratio.

**uncle** · 01-15-2022, 11:04 AM

Pic

**MikeB** · 01-15-2022, 01:23 PM

Quote:

Originally Posted by uncle

Is the rear axle a five or six lug. What year is your truck? About 95% of the 70 model trucks that I’ve had had the same width housing as 71 and 72. I’m not saying they all do but most that I’ve experienced have.

I know GM went to a wider width on the 70 models, but possibly not the earliest ones off the assembly line. And I think 71-72 rear ends were the same width as 70, but starting in 71 they went to 5-lug axles.

My 69 really looked goofy with its narrow rear end, even with larger 235 tires. Finally went to 255 tires on 8" Rallys which fill the wheel wells perfectly.

`

BigBird05 · 01-16-2022, 08:21 AM

5 lug axle length is 31 7/16, 6 lug is 30 3/4.

**MikeB** · 01-16-2022, 11:43 AM

Quote:

Originally Posted by BigBird05

5 lug axle length is 31 7/16, 6 lug is 30 3/4.

01-14-2022, 01:17 PM	#1
Tx70Gmc Registered User Join Date: Dec 2016 Location: Dallas, Tx Posts: 60	Rear-End Identification help Can anyone help identify my rear-end? I posted a reply in a very old thread, but did not have any luck getting responses, so I figured I would try to post a new thread. I have searched the forums and came across a post that referred to some identifying factors, but I'm not sure what it all means. here is the post: http://67-72chevytrucks.com/vboard/s...79#post9018479 Can you help me identify mine? 67890 - GM 12 bolt E120 - May 12, 1970 NF3896838 Axle Stamp = TDA 0521W1 so I think the TDA means its a 3.73 gear and I think the 052 is the 52 day of the year it was built? and I have no clue what the 1W1 means? any ideas? Thanks, Last edited by Tx70Gmc; 01-14-2022 at 03:12 PM.

01-14-2022, 06:00 PM	#2
MikeB Senior Member Join Date: Jul 2000 Location: North Texas Posts: 3,665	Re: Rear-End Identification help Yes, TDA on a 1970 rear end means 3.73 gears. Funny, but on 1971 models TDA means a G30 van with 4.57 gears. I didn't spend a lot of time searching, but can't find anything on 0521W1. __________________ Mike 1969 C10 LWB -- owned for 36 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, recent AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- converted from 250-six to roller cam 350, Vortec heads -- sold 1981 C10 Silverado LWB, 305, TH350C -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then!

01-14-2022, 06:40 PM	#3
Getter-Done Senior Member Join Date: Dec 2009 Location: TN. Posts: 8,671	Re: Rear-End Identification help I did not find the 0521M1 either. I did find this in the link below. Link: https://www.chevyhardcore.com/tech-s...rearend-guide/ __________________ ________________________________________________________________________________________ ____________________________________________ The early bird gets the worm, But the second mouse gets the cheese 84 Chevy K-20 63 Impala (my high school car) http://67-72chevytrucks.com/vboard/s...Crew Cab Build

01-14-2022, 06:57 PM	#4
Tx70Gmc Registered User Join Date: Dec 2016 Location: Dallas, Tx Posts: 60	Re: Rear-End Identification help I read that entire article and it helped with date code, etc but not the 0521W1

01-14-2022, 10:19 PM	#6
BigBird05 Registered User Join Date: Aug 2019 Location: Cheraw Posts: 1,300	Re: Rear-End Identification help Mike B 71 is a different axle than a 70.

01-14-2022, 10:48 PM	#7
BigBird05 Registered User Join Date: Aug 2019 Location: Cheraw Posts: 1,300	Re: Rear-End Identification help I am looking at it a different way. 0521 is May 21st day, W is the plant that assembled the axle, 1 is first shift.

01-15-2022, 10:58 AM	#11
uncle Senior Member Join Date: Aug 2003 Location: Conyers,Ga. Posts: 7,289	Re: Rear-End Identification help Is the rear axle a five or six lug. What year is your truck? About 95% of the 70 model trucks that I’ve had had the same width housing as 71 and 72. I’m not saying they all do but most that I’ve experienced have.

01-15-2022, 11:02 AM	#12
uncle Senior Member Join Date: Aug 2003 Location: Conyers,Ga. Posts: 7,289	Re: Rear-End Identification help I probably didn’t read all the above post very carefully but here’s a post from a board member years ago as far as the code and gear ratio.

01-15-2022, 11:04 AM	#13
uncle Senior Member Join Date: Aug 2003 Location: Conyers,Ga. Posts: 7,289	Re: Rear-End Identification help Pic Attached Images

01-16-2022, 08:21 AM	#15
BigBird05 Registered User Join Date: Aug 2019 Location: Cheraw Posts: 1,300	Re: Rear-End Identification help 5 lug axle length is 31 7/16, 6 lug is 30 3/4.



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