tslsa28

Hello. I am looking at buying a 1974 with manual transmission and 454 engine. I want the tallest rear end gears I can get swapped into it. I think some C3s came with 2.73s so is it as easy and installing the ring and pinion and speedometer driver? Can I go taller than 2.73s? Thanks.

fishslayer143

the 2.73 came in the aluminum Dana 44 Differential cars in the 80-82 years.. a 74 has an Eaton Iron differential .. a 3.08 was the smallest .. I don't know of an aftermarket gear ratio smaller than 3.08 .. speedo driven gear is not hard to change on Trans

by the way, if it gas mileage you want, an Overdrive transmission is far better choice than tiny gears..

derekderek

sounds like you are not a tire smoking hitting second as hard as you can kind of guy. a borg T5 from an 88-92 Camaro or firebird is the most cost-effective 5 speed swap. and least amount of modding-altering to fit.

tslsa28

I agree about the overdrive transmission but as I'm mainly concerned about cruising rpms, I was hoping it would be easy to swap gears and it is much cheaper. There was a 2.73 ratio available in 1975 with the automatic. Do you know if that was same rear end for an easy gear swap? Summitracing.com has the 2.73 ring and pinion.

tslsa28

Thanks and the overdrive would be better overall, just more expensive. I would probably do the Tremec swap as they now have a bolt in kit. The T5 is nice but I have blown one up in a Camaro race car and they don't handle much torque.

2mnyvets

Check that this will fit. About 2 years ago I found the Summit listing on ebay. When I called and tried to order it, it was for a Chevy, not a corvette. A few months later, the listing was still there. I went with 3.08s.

I just went back and rechecked the Summit site, A 2.73 comes up for a 73 corvette, but when you check the application information no corvette is listed.

tslsa28

Yes and I wouldn't completely trust any vendor without really checking into it. But there was an option AY for a 2.73 ratio in 1975 and also 1969 so if the housings are the same as the 1974, there must be someone who hopefully still makes the ring and pinion.

cv67

FInd out what 1st gear the trans has on the car you buy before you make up your mind about rear end gear. If its a 2.20 low a tall gear will have you hating 1st slipping it a lot.
If it has a 3.31 you may just like it....

2mnyvets

Another option: My trans was shot. I went to an Autogear trans gear set with a 3.?? first gear ratio. It is the same as having 4.?? rear in an M21 in first gear. The advantage was I didn't have to cut my car up to make it fit, The disadvantage is that the gear spreads are about 30%. still working on the car, so I don't know how it will run.

caskiguy

http://www.richmondgear.com/auto-parts-product/?crt_formKey=inventory_search&crt_part=r ing-and-pinion&crt_position=%23%28rear%2C+n-a%29%23&crt_differentialcasedesign=cast+ iron+corvette&crt_year=1974&crt_make=che vrolet&crt_modelandsubmodel=corvette

http://www.superchevy.com/how-to/148-0208-gear-ratio-calculating/https://www.crawlpedia.com/rpm_gear_calculator.htm

http://www.vettefacts.com/C3/1974.aspx

GTR1999

There was a discussion here not long ago on factory 273's offered as an option. I didn't recall them used on iron diffs but they were an option with the BB cars, I believe some, maybe one?, ended up in a L88 automatic car? I didn't bother to go back to search though.

Tom used to sell new 273's, I setup one set for my buddy who wanted them in his 76 M20 L48. I thought he would hate them and ride the clutch but he loved them. I didn't drive the car to see for myself though. Tom stopped having them made years ago because no one wanted them. Gear sets are specific for corvette they are not used in any other application. The spiders are but not the R&P. If you really want 273's I would call all the vette vendors they might have an old set of Tom's sitting on their shelf, I doubt you will find any old or NOS GM sets.

mrvette

I have a 308 R&P setting in my desk drawer in the living room for some 21 years now, went o/drive instead, from muncie 4 speed to 200 4r auto for the o/drive......~2400 rpm at 80 mph it has the old 336 still in it... it's for sale, anyone interested PM me.....

OldCarBum

I have a 73, 454 with a TH-400 with 3.36 rear end gearing.
I'm going to a TKO-600RR with 0.82 fifth gear.
I was going through the same dilemma as you until I made the decision to save my money for a year and invest in the 5 speed.
Even with the standard 3.08 option my cruising highway rpm was going to be higher than I wanted it to be.
Going with the 3.36 gears and the .82 5th gear I'll still be at 2374 rpm's at 70.
I don't like the .64 5th gear TKO-600 option because going from 4th to 5th there is about a 900 rpm change which in my opinion is to high especially when you come to a slight incline or just entering a corner or curve.
The 3.08 rear gears would get me to 2180 rpm at 70 but some say the 3.08 and the 2.87 1st gear is getting iffy and I could be riding the clutch more while others say I will be fine.
Either way it's not perfect and I'm still on the fence about running a 3.36 or a 3.08 rear gear.
I also looked at the 2.73 option with my TH-400 and while I found several manufactures who listed a 2.73 for a Corvette, when it came down to it the gears weren't right.
Good luck.

Sky65

I have a complete 2.73 posi diff assembly. The gears are currently in my 65 in a 74 case. I will be removing them this winter and going back to the stock 3.08. PM me if you are interested in buying the diff. There are not many diffs, or even gears for that matter, around. It took me 5-6 years of active searching to find one.

Tom

BLUE1972

I did / helped a friends 70 with the big block and the SST kit - 5 speed. .6 overdrive. 3.08 rear.

the car cruses fine and around town it's a little better then factory because the first gear is lower than his close ratio was. It's an A/C car.

For the cost of the 5 speed you get the best of both worlds, and Silver Sports kit makes the 5 speed look factory.

I have the 3.55 rear and .6 overdrive with a SB and love it.

tslsa28

Tom, I haven't bought the car yet but am looking. Can you just sell the ring and pinion and would it fit right into the differential in a 74 big block with manual?

Sky65

MCMLXIX

I am interested in your 2.73 diff.
When do you think it might be available and how much do you want for it?

Sky65

PM sent
Tom

tslsa28

Tom, hello and I know it's old post but did you ever separate the ring and pinion and want to sell them?

Arthur