70 LT1 half shafts

[Peter L.]

Are the 70 LT1 half shafts the same as the other small blocks or are they the same as the big blocks?

peter

[Wayne K.]

Re: 70 LT1 half shafts

Surprised you haven't heard from a current LT-1 owner but as I recall (I owned a 70 LT-1 from about 72-80) they had bolt on caps.

[Jack H.]

Re: 70 LT1 half shafts

The current edition of the '70-72 Judging Guide provides rear axle codes for each year of production. In 1970, six of these codes are flagged with an 'H' designator following the gear ratio call out.

The descriptive text says we believe this designates 'heavy duty' where the half shaft attachment would be via block-type caps vs. U-shaped clamps.

[Joe L.]

Re: 70 LT1 half shafts

Jack, Wayne, and Peter-----


Actually, the installed differential carrier unit (i.e. with u-bolt or cap type axles) is unrelated to the half shafts installed.

I believe that 1970-72 LT-1's used the same half-shafts as big blocks. I'm not 100% certain of this, but I'm about 95% sure that 1972 LT-1 did, about 90% sure that 1971 LT-1 did, and about 85% sure that 1970 LT-1 did.

[Wayne K.]

Re: 70 LT1 half shafts

Jack, Wayne, and Peter-----


Actually, the installed differential carrier unit (i.e. with u-bolt or cap type axles) is unrelated to the half shafts installed.

I believe that 1970-72 LT-1's used the same half-shafts as big blocks. I'm not 100% certain of this, but I'm about 95% sure that 1972 LT-1 did, about 90% sure that 1971 LT-1 did, and about 85% sure that 1970 LT-1 did.

Good read Joe. I read something into the question. I do not know if the actual half shafts were the same as the big block, only thought I remembered how they were attached.

Wayne

[Jack H.]

Re: 70 LT1 half shafts

Yes, the same half-shaft PN's are called out for SB and BB use. The manner of attachment at the differential changes (u-bolt vs. cap/strap) depending on configuration (high horse SB + BB's used the cap/strap method).

[Joe L.]

Re: 70 LT1 half shafts

Yes, the same half-shaft PN's are called out for SB and BB use. The manner of attachment at the differential changes (u-bolt vs. cap/strap) depending on configuration (high horse SB + BB's used the cap/strap method).

Jack-----


Where is the same half shaft called out for both small block and big block use?

[Kenneth B.]

Re: 70 LT1 half shafts

Are the 70 LT1 half shafts the same as the other small blocks or are they the same as the big blocks?

peter

I looked at my 2 LT-1'S & my 454. The all looked the same with the cast cap/strap? No U bolts. Half shafts looked the same but I did not measure them. Terry where are you!
KEN

[Jack H.]

Re: 70 LT1 half shafts

Well, you may be onto something here I overlooked, Joe. But, if so it's wasn't for lack of due diligence...

First, the P&A Catalogs ('72 and '82 versions) I checked call out only one half shaft for all 63-79 Corvettes. But, as we know, service didn't always stock correct/factory original parts IF they could achieve inventory reduction by having a 'one fits all' replacement.

So, I then did a 'quickie' check of the AIM book(s). In '65 (first BB) and '67 two different PN's are called out for SB and BB half shafts (3847899 for SB and 3882785 for BB). These call outs were nicely supported by drawings showing the standard vs. optional parts along with their different fasteners (U-bolt versus BB cap/strap).

OK, that settles the matter for mid-year cars. But, this thread is about Shark cars, a '70 LT-1 in particular. I don't have a '70 AIM handy, but I do have a '71 AIM and the LT-1 option was common to '70-72. So, I check there.

The LT-1 option calls for the same carrier and axle shafts as the LS-5 under non-illustrated parts. I flip to LS-5 and notice the ABSENSE of a specific drawing akin to prior era BB's, so I check the non-illustrated parts list for information.

It calls out a differnce in Rear Hubs & Bearing citing UPC Section 4A5 refering us to the Bill of Materials. There is NO similar note calling for any non-illustrated differences in UPC Section 4A4 where the half shafts and their fasteners are called out.

Ergo, I'm forced to conclude the half shafts were the same as the base car or there's been a long-standing error in the AIM drawings. Art Armstrong might have more for for us on that.

[Joe L.]

Re: 70 LT1 half shafts

Well, you may be onto something here I overlooked, Joe. But, if so it's wasn't for lack of due diligence...

First, the P&A Catalogs ('72 and '82 versions) I checked call out only one half shaft for all 63-79 Corvettes. But, as we know, service didn't always stock correct/factory original parts IF they could achieve inventory reduction by having a 'one fits all' replacement.

So, I then did a 'quickie' check of the AIM book(s). In '65 (first BB) and '67 two different PN's are called out for SB and BB half shafts (3847899 for SB and 3882785 for BB). These call outs were nicely supported by drawings showing the standard vs. optional parts along with their different fasteners (U-bolt versus BB cap/strap).

OK, that settles the matter for mid-year cars. But, this thread is about Shark cars, a '70 LT-1 in particular. I don't have a '70 AIM handy, but I do have a '71 AIM and the LT-1 option was common to '70-72. So, I check there.

The LT-1 option calls for the same carrier and axle shafts as the LS-5 under non-illustrated parts. I flip to LS-5 and notice the ABSENSE of a specific drawing akin to prior era BB's, so I check the non-illustrated parts list for information.

It calls out a differnce in Rear Hubs & Bearing citing UPC Section 4A5 refering us to the Bill of Materials. There is NO similar note calling for any non-illustrated differences in UPC Section 4A4 where the half shafts and their fasteners are called out.

Ergo, I'm forced to conclude the half shafts were the same as the base car or there's been a long-standing error in the AIM drawings. Art Armstrong might have more for for us on that.

Jack-----


They were not the same.

Most, but not all, 1964 through mid 1974 Corvettes with small block used half shaft GM #3832044. In PRODUCTION, this was a half-shaft assembly, including u-joints, known as GM #3847899.

1965 through mid-1974 big blocks used half shaft GM #3872908. In PRODUCTION, this was half-shaft assembly GM #3882785.

As I described previously, I am now very confident that 1970-72 LT-1 and 1973-mid 74 L-82 also used the GM #3872908 half shaft, aka PRODUCTION GM #3882785. I believe that 1969 L-46 used the standard small block half shaft. I don't know what 1970 L-46 used, though.

In SERVICE, the GM #3832044 was available for 63-65 small blocks. Beginning in 1965, the GM #3872908 was added for big blocks. In March, 1966 the GM #3832044 was discontinued from SERVICE and replaced by the GM #3872908 for all 63+ Corvette applications. However, the 3832044 continued to be part of the PRODUCTION GM #3847899 assembly right through mid 1974.

The difference between the 3832044/3847899 and the 3872908/3882785 was that the latter was shot-peened and the former was not.

[Kenneth B.]

Re: 70 LT1 half shafts

Jack-----


They were not the same.

Most, but not all, 1964 through mid 1974 Corvettes with small block used half shaft GM #3832044. In PRODUCTION, this was a half-shaft assembly, including u-joints, known as GM #3847899.

1965 through mid-1974 big blocks used half shaft GM #3872908. In PRODUCTION, this was half-shaft assembly GM #3882785.

As I described previously, I am now very confident that 1970-72 LT-1 and 1973-mid 74 L-82 also used the GM #3872908 half shaft, aka PRODUCTION GM #3882785. I believe that 1969 L-46 used the standard small block half shaft. I don't know what 1970 L-46 used, though.

In SERVICE, the GM #3832044 was available for 63-65 small blocks. Beginning in 1965, the GM #3872908 was added for big blocks. In March, 1966 the GM #3832044 was discontinued from SERVICE and replaced by the GM #3872908 for all 63+ Corvette applications. However, the 3832044 continued to be part of the PRODUCTION GM #3847899 assembly right through mid 1974.

The difference between the 3832044/3847899 and the 3872908/3882785 was that the latter was shot-peened and the former was not.

This is starting to make my head hurt. Can we tell without seeing a part # if the half shafts are correct on LT-1"S
KEN

[Joe L.]

Re: 70 LT1 half shafts

This is starting to make my head hurt. Can we tell without seeing a part # if the half shafts are correct on LT-1"S
KEN

Ken-----


You generally won't see a part number on original half shafts, so that's out as a way to ID them.

If I'm correct about the 70-72 LT-1 half shafts, they will have a shot-peened finish. It's as simple as that.

There were only 2 half shafts used during the 64 to mid 74 period. Their configuration was identical EXCEPT for the shot-peening.

[Tim G.]

Re: 70 LT1 half shafts

I had a wonderful and original 1970 LT1 in my hands for quite a while last year and its original rear end had half shafts with caps securing them to the differential. My '72 LT1 also had caps securing it to the differential.
My understanding is that all LT1's have caps, but I've seen some that don't. They may have had a replacement rear or they may not have been a real LT1, I don't know. If I see an LT1 without caps, I'm very cautious if I'm looking at a purchase.

[Terry M.]

Re: 70 LT1 half shafts

OK Ken, I'll stop sitting this one out -- just to please you ol' buddy.

The original question did not involve the issue of mounting of the differential end u-joint. It simply asked if the LT1 half-shafts were the same as Big Block or Small Block.

I don't know the answer to that, and my resource material that would answer that is not readily available. Some day I'll look it up, but why not believe Joe L? He probably has better reference material than I do.