couple questions

[wreckedchevy]

I was hoping one of you could help me decode the number's off my rear-end I know it's a 12 bolt posi was wanting to find out the gear ratio

CB05PC21

also I was wondering if any of you knew if the 80's style blade temp sensor works with the stock temp gauge. My 305 still had the original temp sensor in the side of the block but when we put it in my truck we stuck the old nail head sensor into the thermostat housing and I've been using it but when I did the rewire I switched to the blade style on the side of the block now I have no temp. not sure if it's bad sensor or just doesn't work with the gauge.

Thanks for the help

[68gmsee]

First, is it the original rear end with 6 bolt axles? If so, did you get the number from the pumpkin or on the passenger side axle tube. Mine was on top and covered in grime. I got to it by removing the rear passenger side tire.

If you want to be exact the best thing to do is to remove the cover and check the gears. Remember that unless you've owned the truck someone else may have done some changes in the last 40 plus years. You can do a search or google on how to determine ratio.

[wreckedchevy]

i'm the second owner and I've had it almost as long as the original owner did. the number's came off the passenger side tube (sent the teenager to get them) hopefully she did good :-) it is the original rear end with the 6 bolt axles.

[GMCPaul]

Originally Posted by wreckedchevy

I was hoping one of you could help me decode the number's off my rear-end I know it's a 12 bolt posi was wanting to find out the gear ratio

CB05PC21

also I was wondering if any of you knew if the 80's style blade temp sensor works with the stock temp gauge. My 305 still had the original temp sensor in the side of the block but when we put it in my truck we stuck the old nail head sensor into the thermostat housing and I've been using it but when I did the rewire I switched to the blade style on the side of the block now I have no temp. not sure if it's bad sensor or just doesn't work with the gauge.

Thanks for the help

3:36 rear gears rear end from a 69 El Camino
Paul @ GMCPauls

[LockDoc]

-
Here is a link to the '67-'72 charts I posted a while back.

http://67-72chevytrucks.com/vboard/s...d.php?t=578793

LockDoc

[Tinkermc]

this Forum is the best info site I have run across

[wreckedchevy]

Originally Posted by GMCPaul

3:36 rear gears rear end from a 69 El Camino
Paul @ GMCPauls

that's what I kept coming up with when I was googling last night but they were all car sites I had assumed that the ratio code was also used in car's but wasn't they same as my truck. it is extremely low geared 35 in 4th and i'm running 4 barrels wide open. I can't believe they would have swapped the rearend in the truck unless it didn't come with the 12bolt i'm second owner the original owner did not spend any money on it he actually blew a tire and instead of replacing the 16" he had a 15" car tire on it and was driving it like that. they were very dirt poor famer's when he died they auctioned off everything that's how I got the truck.

i'm going to go jack it up and spin the tire and count drive shaft rotations and see where it's at. thanks for the info Paul.

any ideas on that newer style temp sender?

[wreckedchevy]

as stated originally I sent the teenager out to get the number off the axle tube even showed a picture from this site showing exactly where the number was and apparently when she returns I have to have a long talk about the difference between a rear end and a shock absorber. I truly apologize for that and any time wasted looking up that number although I am impressed that the model off my shock actually decodes to a rear end from a el camino (which is why I posted the question in the first place cause that's what I kept finding as well).



the correct number's gathered by myself are HC 06 03 which tell's me it's a 3:73 (thanks lockdoc) and I confirmed it buy rotating tire one turn and counting drive shaft rotation's. anyone recommend a good gear to run to keep the rpm's down on the highway. this thing is so low I can leave it in 4th start the truck in gear and drive away like it's an automatic

[LockDoc]

Originally Posted by wreckedchevy

as stated originally I sent the teenager out to get the number off the axle tube even showed a picture from this site showing exactly where the number was and apparently when she returns I have to have a long talk about the difference between a rear end and a shock absorber. I truly apologize for that and any time wasted looking up that number although I am impressed that the model off my shock actually decodes to a rear end from a el camino (which is why I posted the question in the first place cause that's what I kept finding as well).

the correct number's gathered by myself are HC 06 03 which tell's me it's a 3:73 (thanks lockdoc) and I confirmed it buy rotating tire one turn and counting drive shaft rotation's. anyone recommend a good gear to run to keep the rpm's down on the highway. this thing is so low I can leave it in 4th start the truck in gear and drive away like it's an automatic

That's funny. The poor girl is probably feeling bad now. Tell her I said that's alright, that's how you learn... Trial & error...

No problem on the link. You might want to try a 3.07 rear and see if that helps you out.

LockDoc

[Lattimer]

I have a 3.73 in my truck and its a little buzzy on the highway, but it turns 3000 rpm at 70 mph (car 4-speed, 1:1 4th gear). Compared to my nice new 6 speed auto equipped Tundra (that turns 1900 at 70) it sounds like its wound pretty tight. But 3000 rpm is not a problem.

My little 327 won't pull away in 4th, but it can do 1st to 4th pretty easily and not strain much. I'd like to drop my rear end ratio for lower highway rpm, but I'm afraid I'll lose too much on takeoff.

All that said, I'm keeping it as-is until I decide to part with enough $$ to go with an overdrive trans. I'm keeping the 3.73's.

[wreckedchevy]

that sounds about were I was before but I just went to a set of 255/60 15's (freebie) and it's a lot lower now and of course everywhere in Montana is at least 100 miles away so lots of highway use. i'll be easy on her when she get's back, she's at the age were hating me is coming any day so i''m trying to enjoy her sudden interest in rusty gold while it last.

[wreckedchevy]

http://www.ebay.com/itm/Gm-Chevy-Tru...cf2874&vxp=mtr

you guys think this is the critter? i'm assuming all 12 bolt truck's are the same ( I hate assumptions)

[GMCPaul]

Originally Posted by wreckedchevy

that's what I kept coming up with when I was googling last night but they were all car sites I had assumed that the ratio code was also used in car's but wasn't they same as my truck. it is extremely low geared 35 in 4th and i'm running 4 barrels wide open. I can't believe they would have swapped the rearend in the truck unless it didn't come with the 12bolt i'm second owner the original owner did not spend any money on it he actually blew a tire and instead of replacing the 16" he had a 15" car tire on it and was driving it like that. they were very dirt poor famer's when he died they auctioned off everything that's how I got the truck.

i'm going to go jack it up and spin the tire and count drive shaft rotations and see where it's at. thanks for the info Paul.

any ideas on that newer style temp sender?

Blade style temp sender will work you don't have to have one with the nail head style so the 1 you have installed is bad.
Love where your daughter got the axle code. LOL
She know what a axle tube is now right?
Paul @ GMCPauls

[wreckedchevy]

I just got a tach installed and i'm running 4000rpm at 40 mph. is my best option to go to 3.07 gears? I didn't get that set off of ebay cause I asked the seller and he started rattling off a whole lot of parts I need. to go from 3.73 to 3.07 do you really have to pretty much gut the rear end and start over? also is the 4 speed tranny's geared really low or is 4th 1:1 ? thanks all.

[mmiddle]

Something is not right????? 4grand at 40???? Something is bad wrong.
Ether the clutch is serously slipping
you have 5:13 gears
extra small tires.
messed up tach
or a combination of....
Like I say, something is bad wrong.

[wreckedchevy]

255/60r15 is what I have on the back. it has always been really low geared but since I put those tires on it's been ridiculous. I've smoked enough clutches back in the day to know it's not slipping. tach is up in the air it's a loaner I temped in to see what rpm's are doing.

[Lattimer]

That's a 27" diameter tire. Something is very wrong to have RPM's that high at that speed. I run a 29" tall tire 255/70-15, I have 3.73 gears, and at 70 mph I turn 3000 rpm. In the last 6 months I've had 3 different tachs (long story), and they all read the same. With your tires I could see you turning maybe 3300 at 70.

Regardless of transmission, the high gear in all of them is 1:1 if its not an over drive trans.

[Lattimer]

I drove my Chevy in to work this morning and double checked the rpm. 40 mph in 4th gear is 1800 rpm. My tires are a touch taller than yours, so you might be 2000 rpm. I think your tach is reading double the actual rpm. If it has a switch for 4/6/8 cylinder operation, its probably on the wrong setting.

At 70 mph (verified on gps), I turn 3200 rpm. That's 1:1 4th gear and 3.73 rear end, 29" tall tires, reading on the factory style repro tach that I just installed with my new gauge cluster.

[Lattimer]

Originally Posted by wreckedchevy

I just got a tach installed and i'm running 4000rpm at 40 mph. is my best option to go to 3.07 gears? I didn't get that set off of ebay cause I asked the seller and he started rattling off a whole lot of parts I need. to go from 3.73 to 3.07 do you really have to pretty much gut the rear end and start over? also is the 4 speed tranny's geared really low or is 4th 1:1 ? thanks all.

Also on the rear end swap, from my understanding to swap from 3.73 to 3.07 you have to swap the carrier. So its basically everything but the axle shafts gets replaced.

[wreckedchevy]

Originally Posted by Lattimer

Also on the rear end swap, from my understanding to swap from 3.73 to 3.07 you have to swap the carrier. So its basically everything but the axle shafts gets replaced.

thanks that's what I was trying to confirm. on the tach it's a auto meter 2305 seems to be the only one on the net I can't find the switch setting for. a mechanic loaned it to me said it was already set for 8cyl. most the ones I can find online have dip switches this one has a 3 position switch.