1972 c10 12 bolt 373 to 308 conversion

[mike16]

Just got two quotes on the conversion and a couple of caveates. One guy quoted me 1000 bucks for new gear/bearings on my carrier,

another guy quoted me 400-500 using a used ring and pinion and carrier plus new bearings,

the second guy also warned me that a 308 carrier is different from a 373 carier.

He also stated that some 12 bolts do not have the internal clearance for a 308 ring and pinion and you cannot tell until you get it all apart.

He also has a 342 gear set that will fit my 12 bolt without fuss same price.

I drove my truck for the first time this week and realise how "geared" it is with the 373's.

I only have a 307 with a 3 speed and dont often carry heavey loads but I do drive long distances so milage is an issue.

open for discussion? I got about two weeks to deside befor I go cross country in it

[67cheby]

are the 3.73s for sale , i would be interested in buying them, i have 3.08s in mine and a 700 r4, we could do some trading

[mike16]

Mike, I'm not going to go into this with you here but I am PM'ing you.
oldiron

I also forgot to mention that the cheaper gear installer in the post above mentioned that a complete rear goes for about 400 bucks but my rear is origional and in very good shape.

[BluTrukker]

Seriously? The best way to ensure that nobody helps you with your gear problem is to get angry about the forum. The people on this site have a wealth of knowledge about these trucks and are willing to help whenever they can, but they won't if you bash our beloved forum. Having said that, I would love to help you out, but I don't have much experience with rear end gear swaps.

[Fitz]

Originally Posted by mike16

One guy quoted me 1000 bucks for new gear/bearings on my carrier,

another guy quoted me 400-500 using a used ring and pinion and carrier plus new bearings,

I got about two weeks to deside befor I go cross country in it

OUCH! I think you have been given some bad info...DTS (www.drivetrainspecialists.com) shows the following ratios for a GM 12 bolt 8.875 truck rear:

4.88, 4.56, 4.11, 3.73, 3.48 & 3.07 all of them fit the same open carrier or Posi center section and are fully interchangeable AND these gearsets are all priced between 180.00 and 225.00. When I bought the 4.11 gearset for my truck I also purchased an Eaton Posi center section (420.00) and new bearings, shims and a crush sleeve for about 60.00. That's way short of a grand and that replaced everything in the housing but the axles!

[71tahoe]

Originally Posted by mike16

Just got two quotes on the conversion and a couple of caveates. One guy quoted me 1000 bucks for new gear/bearings on my carrier,

another guy quoted me 400-500 using a used ring and pinion and carrier plus new bearings,

the second guy also warned me that a 308 carrier is different from a 373 carier.

He also stated that some 12 bolts do not have the internal clearance for a 308 ring and pinion and you cannot tell until you get it all apart.

He also has a 342 gear set that will fit my 12 bolt without fuss same price.

I drove my truck for the first time this week and realise how "geared" it is with the 373's.

I only have a 307 with a 3 speed and dont often carry heavey loads but I do drive long distances so milage is an issue.

open for discussion? I got about two weeks to deside befor I go cross country in it

I would think for $1000 you could get posi, all new bearings, seals, axle bearings and seals and the brakes redone with new drums.

Look at summit racing for gear sets and install kits. Probably about $300. They even sell gear sets to fit other carriers although your combo might not apply. If he will guarantee his work with a used set of gears for $400 it sounds like a good deal.

[gcburdic]

Actually, I thought there are 2 different series (3 & 4) carriers pending gear ratio....that site says so as well...3.90 and below is one and the 4.11 and up is the other....

[capev86]

the 3.07 is just tooo lame for a truck. the 3.73 gear is way more peppy. even a 3.40-3.50 range rear gear is good compromise if you don't do much towing. if you need lower rpms and better highway fuel economy, your money is best spent on an overdrive.....that will give you a 2.60 final drive with 3.73 rear gear (compare that to a straight 3.07) so you get the best of both worlds. a 200 or 700r4, 4l80 and allison are all good transmissions. the separate GV unit is restrictively expensive and only gives you a .85 overdrive ratio instead of a .7 in most factory units.

[Hottrucks]

ok I need to ask...I have 308 gears in a complete axle... I also have a complete 4:11 axle that I plan to put in this week...heres the problem I hate both gears and am looking for a set of 373's ...which houseing do they fit??

most of my driving is 55 mph or less with an occational trip to Ct (180 miles)

[LMN8UR]

Originally Posted by Hottrucks

ok I need to ask...I have 308 gears in a complete axle... I also have a complete 4:11 axle that I plan to put in this week...heres the problem I hate both gears and am looking for a set of 373's ...which houseing do they fit??

most of my driving is 55 mph or less with an occational trip to Ct (180 miles)

The 3:73 will fit in the (Series 4) 4:11. I currently have 2:76 gears in my '72 with an overdrive tranny. (65 mph = 1400 rpm) Good thing I've got tons of torque! She ain't much off the line, but I can drop her down to 3rd at 70 mph and eat a HEMI Ram. I admit, I'm not man enough to see how fast she'll go!

Series 3 is good for 3:43 and <, Series 4 is good for 3:43 and >. Now there several manufacturers that have crossed these boundaries.

[Tx Firefighter]

Twice in the last few years I have swapped complete 3.73 rearends to other guys for 3.07 rearends. Even trade and we were both happy. Saves setup hassles and a bunch of money.

As far as 3.07 being too lame for a truck, I drive 90 miles round trip to work on high speed roads. They work fine for me. I can break the tires loose from a roll in 2nd gear (manual trans) every time so it's enough gear for acceleration for most people and it is nice and calm at 70 miles per hour.