gear ratio

[1966FLEETSIDE]

i have a 63 fleet can someone tell me what else rear axle i can swap for a faster ride????any help is apreciated thx its got a 292 3speed on the floor thx its a slo-poke top speed is 45 mph

[61_FL_Apache]

What do you have now?

[AcampoDave]

Is it slow because it's wound up tight and screamin' at 45 m.p.h or because it's pedal to the metal can't go any faster?

[hotrod66]

I put a axial out of 84 chev with 3.08 ratio, I had to weld mounts. She is slow of the line but hums down the road running 70 mph only pulling 2100rpm

[luvbowties]

Originally Posted by 1966FLEETSIDE

i have a 63 fleet can someone tell me what else rear axle i can swap for a faster ride????any help is apreciated thx its got a 292 3speed on the floor thx its a slo-poke top speed is 45 mph

I'm assuming you have a big-numbered ratio(big, like 4.10, 4.56, etc)and its running out of rpm's around that 45 mark--it was designed for pulling, not cruising. Also assuming you need a smaller-numbered ratio(like a 3.73, 3.08, etc.).

I'd guess a 292 would have sufficient torque to pull a 3.08 just fine. I actually have a '71 C10 3.08 diff'l right now--a direct bolt-in for '64-'66(you'd need to check if '71's would also bolt into your '63), as trailing arm mounts, coil spring perches, and panhard bar mounts are in correct position for those '60's pickups. Have had it for 3 years in case I decide to calm down that strong 1st gear in my 700R4 with its present 3.73. Had I had only the 3.08 when assembling my truck, she'd be in there right now!

Does yours have trailing arms and coil springs? If so, a '71 should fit, if you can locate one. Our local yards have long ago sold/crushed their inventory of that era.

Just my opinions, mind you. Maybe other, more knowledgeable than I will chime in and help.

Luck, and.......we always need pictures!
Sam

[TJ's Chevy]

292 has plenty of torque to pull a 3.08.1 ratio with a stock 28 or 29 inch tire...I'd suggest going to a taller tire and 3.42.1 so you still have good off the line acceleration. Either that or an od trans.

[1966FLEETSIDE]

Thanks for the input fellas ,that's slot of good information I will post pictures as soon as I get them thx

[1966FLEETSIDE]

Oh and by the way it does have coils w trailing arms luvbowties

[Coltronist]

Find out what your ratio is, you can jack up the rear end and rotate the tire one full rotation and count how many times the drive shaft rotates for one full rotation of the tire. I.E. If the driveshaft rotates just a smidge over 3 rotations then your diff is about 3:08.

The lower the number (I.E. 3:08) the higher the ratio. The higher the ratio the more top speed you can pull, but you are decreasing torque.

The higher the number (I.E. 4:75) the lower your ratio will be. Which means you have greater torque but less top speed.

[dracko]

I dig 3.73 with OD trans but agree 3.42 is a great ratio for all aspects of driving

[LVPhotos]

Here is the chart I post to every ratio question. I run a 28.5" tire a 3.73 rear and od and I am right in the sweet spot.

[endlessearth]

Originally Posted by dracko

I dig 3.73 with OD trans but agree 3.42 is a great ratio for all aspects of driving

Agree. I swapped an Eaton with 4.56 for a '71 12 bolt with 3.73 gears and a posi. I have a Tremec 5-speed with an OD and I get both quick launches and can cruise at 75mph at 2,100 RPMs.

[1966FLEETSIDE]

Ok so how do I accurately check what gear ratio I have now?thx

[LVPhotos]

Jack the weels off the ground, mark tire and shaft, rotate and count driveshaft rotation. Just shy of 4 is 3.73, little more 4.11, rare to me is 3.42. Or do a oil change and drop the cover.

[Captainfab]

Pull the cover and have a look. The differential is possibly the most neglected part of a truck right along with a manual trans. I can almost guarantee that the oil needs to be changed. It will only cost you a cover gasket and a couple quarts of gear oil plus your time. In exchange you will know for sure what your gear ratio is and the condition of the internals. Plus the peace of mind knowing that you just serviced your differential and it should be good for quite a few more miles.

Originally Posted by 1966FLEETSIDE

Ok so how do I accurately check what gear ratio I have now?thx

[TJ's Chevy]

Throw a tach on it....drive it 55 and see what rpms yer getting...then go to a gearing calculator and see. Works for me.

[vince1]

If I am correct on the 63's the panhard bar may mount to a welded bracket close to the end of the RH axle tube. The panhard bar is shorter on the 65's and newer and mounts to a lug in the center housing. The bracket on the LH frame rail between the two would be slightly different due to the different geometry. I had a 3.73 64 diff in my 66 for a while but had to really reef on the bar to get it into the bracket.

Since then I have put in a 70 3.08 which was a proper direct bolt in to the 66. The 70 and newer are 1 1/2" wider and I believe 70 is the last year of the six stud axles before changing over to five stud. IMO with stock wheels and the extra width it looks better.

If you want to change out the diff to 3.08 get one from 64 or older or get the frame rail bracket and panhard bar with the newer 65 and up center section mount type. I think the frame rail in my 66 was drilled for either bracket.

[vince1]

If I am correct on the 63's the panhard bar may mount to a welded bracket close to the end of the RH axle tube. The panhard bar is shorter on the 65's and newer and mounts to a lug in the center housing. The bracket on the LH frame rail between the two would be slightly different due to the different geometry. I had a 3.73 64 diff in my 66 for a while but had to really reef on the bar to get it into the bracket.

Since then I have put in a 70 3.08 which was a proper direct bolt in to the 66. The 70 and newer are 1 1/2" wider and I believe 70 is the last year of the six stud axles before changing over to five stud. IMO with stock wheels and the extra width it looks better.

If you want to change out the diff to 3.08 get one from 64 or older or get the frame rail bracket and panhard bar with the newer 65 and up center section mount type. I think the frame rail in my 66 was drilled for either bracket.

[1966FLEETSIDE]

Ok so I rotated tire one full turn and marked drive shaft and I wanna say it's almost an even match with one full turn ????? So what does that mean???

[dracko]

Okay you have 1:1 gear ratio. Haha, no that would lead to some high revs. really tho, if you mark the tire and driveshaft, turn the tire one rotation and see how many times the driveshaft rotates during the tire spin.

[vince1]

The way I would do it is mark the wheel and then turn the driveshaft counting the turns until the wheel makes two revolutions. That is with one wheel still on the ground.

[vince1]

I think you have a 3.73 which is most common or maybe a 4.11 or similar if they made them. If you count slightly less than 4 turns of the drive shaft you have the 3.73, slightly more and it will be around a 4.11.

[frankslagoon]

I just put a 66 rear end in my 63. bolted right up. just had to make the panhead bar fit. nice getten rid of those pesky 17 spline axles and press on backing plates that come on the 63.

[1966FLEETSIDE]

I figured out I do have a 3.73 gear ratio,now what?

[TJ's Chevy]

Pending on tire size an OD trans would be your best bet...and something is also telling me that your 292 isn't tuned very well. I was able to make almost 75 with my bone stock 292...took a little bit but it got there...and ever since I put the 4 barrel and headers on...I can easily get up there...dang I've hit almost 90 with the thing. lol Was to scared to keep it going faster.... I'd suggest checking out that engine to...if my stock 48 year old 292 could achieve 75 miles an hour with 3.73 gear ratio and 30 inch tire then yours should to. Try some tuning...and a good od trans would be a T5 out of an S10 with the V6...1995 model year I believe. Langdon Stovebolt. com will have all the info needed on that and a number to call to talk with Tom. Here's another thing to...a 292 with a stock single barrel is starving for fuel at higher rpms...With the 4 barrel I'm able to get to 4000 rpm in 4th...and it still climbs. So a good close ratio tranny would be good, or do some tuning. I wouldn't put in a taller ratio because the taller the gearing, the more torque wasted.