Less RPM's

redvettemike · November 6th, 2009, 08:15 PM

I have a nice '71 442. It has a th400 and the standard rear end for an a/c car (3.23?). This trans/gearing gets me close to 3000rpm at 70mph. I have been considering some options on reducing the engine operating speed. I have considered a 700r4, a 2004r, a Gear Vendor overdrive unit to try to lower the rpm's (at age 60 I am much more interested in highway cruising than 1/4 mile performance!) I am giving some consideration to going to a higher rear end ratio (actually a lower #) A ratio of 2.72 or 2.56(+/-) would give me the type of cruising rpm's that I want. Will the rear end in this car (all original Olds posi unit) allow the replacement of the existing ring/pinion with the ratio's mentioned?
Thanks for any advice. The engine is the original (but rebuilt) 455. The th400 is the original trans and has been rebuilt 7k miles ago by a prior owner.

BIGJERR · November 6th, 2009, 08:31 PM

Why cut the nuts of a classic muscle car with a huge CI motor? Gas milage? I guess I just dont get this thinking..........455 + 3.55-3.73 gears= Street beast with some manners but with enough gear to get out of its own way,I guess a after market overdrive unit would be the way I would go....My .o2.................Jerr

kaz442 · November 7th, 2009, 12:08 AM

How tall are the rear tires? Might be easy enough to just run a taller tire to give you a little less gear. Probably the cheapest route. JKaz

redvettemike · November 7th, 2009, 03:30 AM

The rear tires are 26" high. Running at a lesser engine speed is just a personal thing-something that I want. I have a '69 Camaro that has a 700r4 and it runs at a less high rpm. However, if I can avoid it, I don't want to have to go through the hassle (and expense) of a trans swap (and I know a 2004r would also fit). I think that Olds had a 'Highway Cruiser' Delta 88 back in the early 70's that had this tall gear rig. I plan to go on the Hot Rod Power Tour in June and would like to have a lesser engine speed on this 2k trip. According to one of the rpm/speed calculators I can save close to 500rpm with a 2.56 change.

70 cutlass s · November 7th, 2009, 06:45 AM

I would suggest 3.08 you would drop rpm on hwy and still have good take off. If you really want 2.56 some one would trade you for your 3.23 I think I have one some where.

2blu442 · November 7th, 2009, 07:56 AM

I believe you would need a different posi carrier to go 2.56 gears. Either swapping out the internals or putting a different rear end and stashing the 3.23 in the corner of the garage would be the simplest. It would be easy to change it back someday if you ever wanted to. Monzaz could answer your questions for sure on what it would take to convert your present rear end.
John

marcar1993 · November 7th, 2009, 10:21 AM

Why on a real 442? Leave it be... How fast do you need to go? 3000rpm at 70 isn't that bad. You could cruise at 80 all day long.
If you really want to lower rpms go with an overdrive trans. Make sure you keep ANY AND ALL stock #'s matching parts. (No I'm not a #'s matching perfectionist btw.)

Bluevista · November 7th, 2009, 03:30 PM

Like 2blu said, just get another rear and stash that one.
Then you can have the best of both worlds.

The 2:56 was optional in '71 and called the "Plains Axle Ratio" along with the 2:73's, for cruisin' the Great Plains I guess?

My '71 Vista Cruiser has a 3:08 rear standard w/air and cruises on the freeway pretty nice but no tach to check RPM's, sort of pointless.

With that 2:56 ratio your top speed before you hit redline would probably be about 175 miles per hour.

marcar1993 · November 10th, 2009, 05:52 AM

Don't forget drag... And lack of acceleration in 3rd gear 1:1 and 2.56's... It would take him forever to get there...
Take it from someone with 2.14 gears (not a typo), while it may be able to do 150mph+, it will take you forever to get there. It will begin flat lining when power starts falling off...

redvettemike · November 10th, 2009, 08:29 AM

I am having second and third thoughts on this entire deal. The car does cruise at 70 ok without a lot of effort. Back in '71 when I had a new '71 442 with this same setup, I never even thought about engine rpm's. The car was designed to run with this set up. Perhaps I should just leave it alone and go on down the road?

marcar1993 · Yesterday, 09:52 AM

Blk71SX · Yesterday, 03:05 PM

you'll lose 600 rpm changing from 3.23 to 2.56

My442 · Yesterday, 03:56 PM

I run 3.91s, and avoid the highway.....

November 6th, 2009, 08:15 PM	#1 (permalink)
redvettemike Registered User Join Date: May 2009 Posts: 71	Less RPM's I have a nice '71 442. It has a th400 and the standard rear end for an a/c car (3.23?). This trans/gearing gets me close to 3000rpm at 70mph. I have been considering some options on reducing the engine operating speed. I have considered a 700r4, a 2004r, a Gear Vendor overdrive unit to try to lower the rpm's (at age 60 I am much more interested in highway cruising than 1/4 mile performance!) I am giving some consideration to going to a higher rear end ratio (actually a lower #) A ratio of 2.72 or 2.56(+/-) would give me the type of cruising rpm's that I want. Will the rear end in this car (all original Olds posi unit) allow the replacement of the existing ring/pinion with the ratio's mentioned? Thanks for any advice. The engine is the original (but rebuilt) 455. The th400 is the original trans and has been rebuilt 7k miles ago by a prior owner.

November 6th, 2009, 08:31 PM	#2 (permalink)
BIGJERR I bleed Oldsmobile Join Date: Dec 2007 Posts: 285	Why cut the nuts of a classic muscle car with a huge CI motor? Gas milage? I guess I just dont get this thinking..........455 + 3.55-3.73 gears= Street beast with some manners but with enough gear to get out of its own way,I guess a after market overdrive unit would be the way I would go....My .o2.................Jerr __________________ DIE HARD OLDS GUY......EAT SLEEP LIVE....OLDSMOBILE

November 7th, 2009, 12:08 AM	#3 (permalink)
kaz442 Registered User Join Date: Sep 2007 Location: NJ Posts: 176	How tall are the rear tires? Might be easy enough to just run a taller tire to give you a little less gear. Probably the cheapest route. JKaz __________________ 72 442 conv. 455 +.060 th400 3.31 12 bolt 70 F85 490 stroker, th400 3.73 Strange S60 87 Buick GN

November 7th, 2009, 07:56 AM	#6 (permalink)
2blu442 Moderator Join Date: Sep 2006 Location: Medford, Oregon Posts: 2,254	I believe you would need a different posi carrier to go 2.56 gears. Either swapping out the internals or putting a different rear end and stashing the 3.23 in the corner of the garage would be the simplest. It would be easy to change it back someday if you ever wanted to. Monzaz could answer your questions for sure on what it would take to convert your present rear end. John __________________ 1964 Cutlass Factory 4spd 1965 442 4spd 1967 442 Auto 1967 Cutlass Convertible 1967 Cutlass four door daily driver 1968 442 Auto 1969 442 W30 Auto 1970 442 4spd 1971 Cutlass Flat Top Wagon 1973 Che*vy 3/4 Ton 454/TH400 Tow Vehicle Only the tow vehicle is finished!

November 7th, 2009, 10:21 AM	#7 (permalink)
marcar1993 Registered User Join Date: Apr 2007 Location: CNJ Posts: 165	Why on a real 442? Leave it be... How fast do you need to go? 3000rpm at 70 isn't that bad. You could cruise at 80 all day long. If you really want to lower rpms go with an overdrive trans. Make sure you keep ANY AND ALL stock #'s matching parts. (No I'm not a #'s matching perfectionist btw.) __________________ 1987 Olds Cutlass- Currently getting a 403 w/#5 heads 1972 Plymouth Satellite Wagon- Grandpa bought it new 1991 Plymouth Acclaim- Daily Driver

November 7th, 2009, 03:30 AM	#4 (permalink)
redvettemike Registered User Join Date: May 2009 Posts: 71	The rear tires are 26" high. Running at a lesser engine speed is just a personal thing-something that I want. I have a '69 Camaro that has a 700r4 and it runs at a less high rpm. However, if I can avoid it, I don't want to have to go through the hassle (and expense) of a trans swap (and I know a 2004r would also fit). I think that Olds had a 'Highway Cruiser' Delta 88 back in the early 70's that had this tall gear rig. I plan to go on the Hot Rod Power Tour in June and would like to have a lesser engine speed on this 2k trip. According to one of the rpm/speed calculators I can save close to 500rpm with a 2.56 change.

November 7th, 2009, 06:45 AM	#5 (permalink)
70 cutlass s Registered User Join Date: Sep 2009 Location: Elizabethtown,KY Posts: 239	I would suggest 3.08 you would drop rpm on hwy and still have good take off. If you really want 2.56 some one would trade you for your 3.23 I think I have one some where.

November 7th, 2009, 03:30 PM	#8 (permalink)
Bluevista Cruisin' the Vistas Join Date: Jul 2006 Location: Northeast Ohio Posts: 1,710	Like 2blu said, just get another rear and stash that one. Then you can have the best of both worlds. The 2:56 was optional in '71 and called the "Plains Axle Ratio" along with the 2:73's, for cruisin' the Great Plains I guess? My '71 Vista Cruiser has a 3:08 rear standard w/air and cruises on the freeway pretty nice but no tach to check RPM's, sort of pointless. With that 2:56 ratio your top speed before you hit redline would probably be about 175 miles per hour.

November 10th, 2009, 05:52 AM	#9 (permalink)
marcar1993 Registered User Join Date: Apr 2007 Location: CNJ Posts: 165	Don't forget drag... And lack of acceleration in 3rd gear 1:1 and 2.56's... It would take him forever to get there... Take it from someone with 2.14 gears (not a typo), while it may be able to do 150mph+, it will take you forever to get there. It will begin flat lining when power starts falling off... __________________ 1987 Olds Cutlass- Currently getting a 403 w/#5 heads 1972 Plymouth Satellite Wagon- Grandpa bought it new 1991 Plymouth Acclaim- Daily Driver

November 10th, 2009, 08:29 AM	#10 (permalink)
redvettemike Registered User Join Date: May 2009 Posts: 71	I am having second and third thoughts on this entire deal. The car does cruise at 70 ok without a lot of effort. Back in '71 when I had a new '71 442 with this same setup, I never even thought about engine rpm's. The car was designed to run with this set up. Perhaps I should just leave it alone and go on down the road?

Yesterday, 09:52 AM	#11 (permalink)
marcar1993 Registered User Join Date: Apr 2007 Location: CNJ Posts: 165	Yes. __________________ 1987 Olds Cutlass- Currently getting a 403 w/#5 heads 1972 Plymouth Satellite Wagon- Grandpa bought it new 1991 Plymouth Acclaim- Daily Driver

Yesterday, 03:05 PM	#12 (permalink)
Blk71SX Registered User Join Date: Nov 2009 Location: NW Arkansas Posts: 8	you'll lose 600 rpm changing from 3.23 to 2.56 __________________ But the Senator, while insisting he was not intoxicated, could not explain his nudity

Yesterday, 03:56 PM	#13 (permalink)
My442 Registered User Join Date: Feb 2009 Posts: 204	I run 3.91s, and avoid the highway.....

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