3:42 gears

[bigblock79]

what came with the 3:42 gears i am long for set. andi got a set of 3:73 just wonder if any one know what truck beside a big block that came 3:42s

[piecesparts]

What axle, do you have? 10 bolt, 12 bolt, etc....

[BowTieOgre]

I have seen several burbs in the 89-91 range that have the GU6 3.42 gears.

[piecesparts]

My 84 has a 12 bolt rear end out of a 78 chevy truck with the 3.42 gears and a posi. This rear end was installed after some gal hit the truck early in life and boggered it up on the curb. I changed out the gears for a set of 3.73 gears and gained some performance and did not really hurt my gas mileage in the deal. My son's 86 had a 3.08 geared 10 bolt open rear end, and I put a 12 bolt 3.73 rear end out of a 4 wheel drive truck and changed the axles to 5 bolt. This changed upped his gas mileage by 2.5 MPG. The 3.08 gears, 700 R4 tranny and Kansas hills did not match well.

[Tx Firefighter]

I parted out a 77 model to get a drivetrain for my shortbed awhile back. It was a factory 350/ TH350, 3.42 truck.

[cjracing15]

My 86 K-10 has 3.42s 10 bolt

[bigblock79]

12 bolt truck rearend. my screams with 3:73 sounds like it comeing thru the hood at 55. much let higher mph. i have had 3 truck with 3:73 and they all been that way. i want 3:42 or 3:08. i am going to try them. i had a 80 camaro with 4:10 and my truck sound like it did the po told me it is 3:73

[GM72K10]

My 87 V20 P/u has 3:42s, 5.7L auto (originally 4M)

[Pyrotechnic]

My 77 GMC Heavy Half came with a 350, Turbo 400, and a 3.42 12 bolt rear. This is a really good compromise between acceleration and highway RPM depending what tire size you have. 3000 RPM is around 65 MPH which is pretty acceptable. These were a really fun gear while I had them.

If you do primarily highway driving like me, as in 3-4+ trips at 75-80 MPH, you will want 3.08's but be warned, your acceleration will suffer quite a bit.

[tkeduk8r]

I really like a 3.42 rear when I have trans that does not have an OD available, specially if you have a SM465 4 speed. A retired teacher buddy of mine had an 84 K20 with a 350, SM465, NP208, 3.42's and 245/75 16's, and we would pull anything we wanted, and still turn acceptable RPM's going down the highway at 65-70. THe taller tire helps too... If I end up going with a SM465 vs. my NV4500 in my 3/4 ton build I WILL find a 3.42 gear set for it...
--Mike

[Walts_restoration]

my 1977 longbed heavy half has 3.40, factory gears, says so on the build sheet, but it might be a 3.42, close enough to vary, and this truck is all original. She does whine up around 75, but she tops off way past the speedo.

[454HO]

My '77 12 bolt has 3.40 gears. This was from a 1/2 ton long bed with factory big block.

[MylilBowTie]

My 86 C20 has 3.42 gears, but its in a 14 bolt sf rear.

[slugish]

have a 3 speed turbo 350 trans.

Had 3.73 gear , in my opinion , not very sreetable

went to a 3.08 , lot better on highway , but like to go to the strip sometimes

now I HAVE 3.42 . iTHINK THE BEST GEAR FOR A 3 SPEED THAT IS MOSTLY STREET DRIVEN , & OCCASIONALY THE STRIP .

[86longbed]

I have 3.42 in my 86...they work fine
not to get off topic but when ya'll are saying streetable are we talking highway or just on the street because 3.73 gears with a 3 spd work just fine on the street and give you a good bit more pick up from a stop but on the highway is where the problems start anything higher than about 55 to 65 and the motor is wound up for any type of long distance traveling but the truck will go way past the speedo for short bursts

[piecesparts]

Originally Posted by 86longbed

I have 3.42 in my 86...they work fine
not to get off topic but when ya'll are saying streetable are we talking highway or just on the street because 3.73 gears with a 3 spd work just fine on the street and give you a good bit more pick up from a stop but on the highway is where the problems start anything higher than about 55 to 65 and the motor is wound up for any type of long distance traveling but the truck will go way past the speedo for short bursts

This whole discussion is about alignment of trannies and gears. I run 3.73 gears in my 84 GMC truck and my son has them in his 86 Chevy. Those rear ends are mated to 700 R4 trannies and th eoverdrive is a great combo with that gear ratio.
At the 75 MPH mark (no one runs 60 to 70 anymore) I am at 2700 RPMs and just starting to breath good on the engine. That also includes a smaller tire than most run on their trucks. I like the response of the 3.73 gears and the roadability of the cruise control and the response on the highways.

[jchav62]

My 83 has 3.08's. They are great for that truck. My 62, which is a little more souped up, has 3.73's with a th350 and a GearVendors overdrive. With the overdrive, they are great! Without OD, not much for highway use.

[piecesparts]

Originally Posted by jchav62

My 83 has 3.08's. They are great for that truck. My 62, which is a little more souped up, has 3.73's with a th350 and a GearVendors overdrive. With the overdrive, they are great! Without OD, not much for highway use.

My son's truck came with the 3.08 gears, but at that time it had a 350C tranny and that worked well for that truck setup. We then put in a 700 R4 and the mileage went out the bottom. The 3.73s gave that mileage back to us and the acceleration is great. Especially with the lower first gear in the 700 tranny.

[bigblock79]

i got a 383 stroker. i got a bulit 350 tranny and 3:73 with a lock right locker. i love the truck for just short trips around town. out on the hwy it suck gas and screams bloody mary. i just want a 342 or 308 and try that i still want to play burn tires and go from 0-100 in a burst. just dont want it to scream to deaf on hwy

[crossy]

Originally Posted by bigblock79

12 bolt truck rearend. my screams with 3:73 sounds like it comeing thru the hood at 55. much let higher mph. i have had 3 truck with 3:73 and they all been that way. i want 3:42 or 3:08. i am going to try them. i had a 80 camaro with 4:10 and my truck sound like it did the po told me it is 3:73

3.42 will only lower you about 250 RPM at any given RPM. I'm sure someone better at math than me can do the formula, but each step change is worth about 250 RPM, so i'm saying 3.08 would drop you 500 from where you are at now w/3.73's.
you cannot count on any certain truck to have a particular gear set you want. OPTIONAL gear ratios were availalbe in all years. 3.08's were not common though before 78.
my 74 has 3.40 stock(3.42) with the 3 speed manual tranny.
crossy