Babafats

Hey there olds folks previous owner threw a 411 gear ratio in my 70 olds rally 350 looking to putt something a little more hwy friendly any suggestions??

66400

Drive to Austin, Tx and I'll sell you a complete rear end for 250. I have 11 70 Cutlass and Cutlass Supremes here.
Henry

M-14

How about a th2004r tranny swap?

Mr Nick

What type of rear end housing is it? Chevy, GM-corporate, Type-O?

3.23, 3.42 and 3.55's are all nice compromises between nice acceleration and some highway manners. I run 3.90's with overdrive and it's fine for 70mph on the highway, but I wish OD was a little deeper so I could cruise at 75 with lower RPM's.

Lars

100 bucks for 3.08 or 3.23 gears or $1500 for overdrive trans. I would run 323's

2blu442

Do you have an automatic or manual transmission? For a factory 4 speed I'd prefer to stay 3.23 or lower. For an automatic you could go as tall as 2.56 which was a common ratio with this vintage. A little slower off the line, but much better if you do a lot of highway driving. My 2 cents....

P.S. if your close enough to Henry I think swapping a complete rear end from a similar vintage Cutlass would be the simplest way to go.

Babafats

i have a 3 speed dan posi

2blu442

I don't know enough about three speeds to have an idea what the ratio is in first gear. That would be the key in my opinion. The reason I say that is years ago I had a 1968 Cutlass with a four speed. When I bought the car it had a 3.08 rear end under it. I felt like I had to slip the clutch to get it off the line, and it seemed to leap across the intersection at traffic lights. I picked up a chevy 3.31 rear end at a swap meet and found it much more comfortable getting the car rolling from a dead stop. If you plan to keep that transmission it might be worthwhile creating a thread asking what rear end ratio's other people have under their cars with factory 3 speeds.


John

Babafats

thats a good idea lol its a 4 speed including reverse lol i know that its the original tranny the previous owner i believe put a shift kit with 2500stall but how would i tell for sure what tranny and rear end i have just so im not going on the previous owners word...by the way when i got the car a year ago the previous owner was a big phony, i had to do so much to get the car road worthy all because he neglected to maintain the vehicle but now shes running great thanks to some TLC from a true respecting owner.

2blu442

I think I misunderstood, I thought you had a 3 speed manual transmission. But it sounds like you've got an automatic. I think you'd be fine with 2.56, 2.78, or 3.08's which were all common in 1970. You wouldn't have the snap off the line but once you got rolling I think you'd find it more comfortable to drive than the 4:11's. Yeah, back to the idea of could you get together with Henry. That would clearly be the easiest way to change it, then you could sell the 4:11 rear end. John

2blu442

I just read back through your last post. If you don't know for sure what the ratio is, you should check that before going any further. I once purchased a 1967 442 project that the owner said had 4.33 gears in the rear end. They turned out to be 3.08 gears

There's a couple ways to check the gear ratio. My favorite would be to remove the rear inspection cover and look for the stamp in the ring gear. It would be something like 11:41 which means 11 teeth on the pinion and 41 teeth on the ring gear. I'll look to see if I can find a photo of this. John

M-14

If your speedometer is accurate, drive the car to 70mph. The tach will tell you the gear ratio. 4,200rpms or so should be 410s. This is figuring in convert slip & speedo inaccuracy. This only works on a tranny with a 1:00 top gear (th350s & 400s, 3sp & 4spds). It won't work the jetaway tranny.

Babafats

austin texas is about 6hrs from new orleans i could do it i would just need to save up some cash for the trip if you could hold on to the rear end, i know that im doing 4000rpm at 50mph my speedo is 10mph off so if im going 60 the speedo reads 70

Mr Nick

To get picky, your speedo is only off by 10mph at one speed. It's off by a given % all the time. Meaning, if you are going 30mph, your speedo won't read 40mph...

12 hours of driving is a lot of gas, cost might not be much different to just ship it on a pallet. But I do enjoy a good parts road trip!

66400

Take your time I have plenty of them at the rate I'm going there will still be some in my estate sale years from now.

Henry

Lars

Go to Texas have a pro help with the swap. Share stories win win

Babafats

well i understand the percentage but i had my buddy drive alongside at 50mph and i matched him and my speedo was reading 60 so maybe the percentage isnt that high??

Babafats

ok so officially planning a trip to austin, what should i expect bring my tools? im unfamiliar with this aspect of mechanic work, am i just picking it up or ?? you guys are so helpfull and so generous thanks again!

Fun71

Or if you're sitting still it won't read 10 mph.

Babafats

hehehe