Stock rear gear ratio info

[SS Tim]

Here is a 70 C10 power team chart for you. It really helps to post what year and series you have when asking a question like this.

[Olive1970]

Thanks Tim, but yes it is a 1970 C10. I didnt know if mine had a different ratio than 3.07 because at 75mph the truck runs at about 3800rpms or so. I do have a built TH350 and 2200 stall converter however so that is probably part of the higher rpms.

[begrab63]

Originally Posted by Olive1970

Wanted to bring up this subject again...my truck SPID is a factory TH350 trans with a 307 engine. Likely rear gear ratio? It seems that most of the 350 engines were 3.08 gear ratio with automatic, didn't know if it would be different on a 307 engine?

Thanks!

I have a 71 C-10 with a 307ci and the rear gear is 3:08...
Posted via Mobile Device

[X Baldwin Motion]

Originally Posted by SS Tim

Here is a 70 C10 power team chart for you. It really helps to post what year and series you have when asking a question like this.

Tim (or anyone) do you have a chart like this for a 68 K20?
I have a burb that was a 6cyl 4spd and a pickup with 327 240hp 4spd
They both have the 10 bolt rear.
The truck screams in 4th gear at 50mph
Thanks

[SS Tim]

Originally Posted by X Baldwin Motion

Tim (or anyone) do you have a chart like this for a 68 K20?
I have a burb that was a 6cyl 4spd and a pickup with 327 240hp 4spd
They both have the 10 bolt rear.
The truck screams in 4th gear at 50mph
Thanks

Thats an easy one, 4.57:1.
All you needed to do was click on the link in my signature, most are there.
http://67-72chevytrucks.com/vboard/s...05&postcount=5

4.57 gears spinning a 31" (stock 7-17.5)tire @ 50 mph = about 2475 rpm, that isn't exactly screaming. The indirect drive T-221 t-cases were never quiet.

[X Baldwin Motion]

Thanks, I found the link right after I posted. So the T221 makes that jet sound normally? It starts whining at 40 and close to 50 I need ear protection.

[SS Tim]

Originally Posted by X Baldwin Motion

Thanks, I found the link right after I posted. So the T221 makes that jet sound normally? It starts whining at 40 and close to 50 I need ear protection.

Have you checked for the proper fluid and level at all the driveline locations? The front axle, both cardon joint balls, transfer and rear axle have a 6k service interval per the driver's handbook pgs 55-57. SAE 90 dino covers most people's use of these trucks. If, with verified correct gear oil and level, its still objectionably noisey I'd look into wear and excessive clearance issues.

Have replacement parts in hand before pulling anything apart.

The idler and output shafts should have zero end play, as in 0.00" is considered ideal as measured with a dial indicator

Suggested reading
68 Overhaul Manual pg 7-111/PDF pg334
68 Service Manual Sections 0 and 3

[X Baldwin Motion]

I've checked front and rear ends, trans and transfer case. All topped up with 90w

Cardan joint balls?


The noise is worse under load, it quiets a bit when I let off the gas, clearly coming from transmission or transfer case

[SS Tim]

Originally Posted by X Baldwin Motion

I've checked front and rear ends, trans and transfer case. All topped up with 90w

Cardan joint balls?


The noise is worse under load, it quiets a bit when I let off the gas, clearly coming from transmission or transfer case

The cardon joint balls are the front axle shaft u-joint swivel housings, they have seperate filler plugs L&R and in checking the driver's handbook are to be filled with SAE140 vs the differential's SAE 90.

[TwoFiftyShifter]

I always thought 3.08 and the granny 4 speed was a sweet combo. No need for overdrive and can still pull a house in first. Just watch the gap between gears!

[SS Tim]

Suggested reading and in hand resources.

[X Baldwin Motion]

Thanks, that's great I wish I had them. Unable to download the manual onto my phone. Just need to see diagram or know where fill is for cardan joints.

[SS Tim]

Here...