I've been thinking about swapping the rear end gears in my Laurentian to something a little more exciting than the highway gears that it currently has. Someone told me the stock 10 bolt in '69 B bodies was one of the weakest made by GM. Is this true? Would I be better off to hold out for a 12 bolt instead of swapping gears in my existing diff? I'd guesstimate my small block is putting out about 300hp. I've been thinking of doing this instead of swapping the 454. I am really on the fence about this swap as my 350 runs so well and has no issues other than a little blue smoke on start up (valve seals). I also thought about swapping a 700r4 and running something like a 3.73 rear end gear.
Once you start swapping gears or up to a 12 bolt, you might as well have a $1000 budget to start.
Is it 2.73 now I suspect?
Personally, I don't see the need for a 12 bolt in a weekend cruiser that is traction limited by pretty much stock tires. Great bragging rights if you have a 12 bolt 3.73 posi for example, but pretty much not needed unless you go up another 50-100 horsepower and sticky tires.
As always, my two cents. With advice, you get what you pay for!!!
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
You've already got the 454, is it ready/almost ready to drop in? I'm sure another 100-150 ft-lbs of torque would help those tires to chirp! AND if you don't plan on hitting the drags regularly or run sticky tires, the rear should hold up fine.
(Then, while you're enjoying all that extra torque, you can keeping your eyes open for a 12 bolt )
Todd my car is in the same situation as yours, completely reliable and foolproof small block with highway gears, mine are 2.73 as confirmed by GMVVS.
Optional gears for my year were 3.08, 3.23, and 3.42.
The situation is the same, my car runs so well I have finally put it out of my mind to change it up. Driving around Toronto is a joke, you can't really accelerate fast from anywhere then I find on the highway the car feels like it has unlimited top end BUT the black and whites are everywhere.
It is what it is and I have accepted that. Besides I have better things to do with my money than pour it into an old car.
Yes, the 454 is just about ready to drop in. I suppose I could install it and if for some reason I wasn't happy I could put the 350 back in. To be honest I really don't have the ambition to do the swap in my garage, working on my back etc. Just swapping out the starter left me sore for two days! My back isn't what it used to be. Now if I had a hoist it would be a different story! A rear end swap I could likely do at Tiny's on a night he isn't busy and use a hoist.
Yes, the 454 is just about ready to drop in. I suppose I could install it and if for some reason I wasn't happy I could put the 350 back in. To be honest I really don't have the ambition to do the swap in my garage, working on my back etc. Just swapping out the starter left me sore for two days! My back isn't what it used to be. Now if I had a hoist it would be a different story! A rear end swap I could likely do at Tiny's on a night he isn't busy and use a hoist.
gettn' old aye ?
once you go big block, you don't go back
just put it in, if not I wouldn't bother with gears-car is probably fine as is-doubt you could do it for $1000
A couple guys and you could have it swapped in a day.....a little longer if you want to clean up the engine bay before dropping in the BB. Let me know if you want a hand..... As for the 700r4, keep in mind you are then looking for a driveshaft or have yours shortened. Possibly moving the crossmember, wiring for it etc.... Just thought I would pass along some things I have found out doing this swap on my Lemans. I would drop in the BB and save for a 3.08 or so posi. The torque will make up the difference and you should still get "decent" (for a BB) mileage on a long haul. Just my thoughts.......
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John
1972 Pontiac Lemans (daughter's car) 2005 Pontiac Grand Am 2004 Ford Explorer Sport Trac
Our 10 bolts are of the 8.125 variety. The 12 bolt being 8.875. With regards to ratio, my '66 wagon has a 3:31 12 bolt and with the powertrain swap from a '70 Parisienne with a 2bbl 350 and a thm350, it buzzes waaay too high at 60mph. It has 245/70R15 tires.
I have a 3:08 12 bolt posi ((no bragging rights)) out of a '68 Biscayne that I am debating of tossing in this weekend. I believe the diff had been swapped because this 3:31 is a non posi but there is a limited slip tag under the spare tire cover. Then maybe add a lock up 350 trans, without having to do driveshaft swap, it should do really well. Besides, it's just a cruiser.
I would leave it with high 2's or early 3's and with the BB, as stated, it should do well on fuel. Unless you are planning on doing many stoplight to stoplight driving!!!
The '67 wagon I just got with a 327 4bbl and a THM400 has 2:73's with 225/70R15 tiresand I am happy with them as it cruises nice down the highway. It is still snappy off the line somewhat for a wagon as well.
On a side note, there seems to be a 12 bolt shortage in Ontario? I know to find a 10 bolt here in Saskatchewan is a rareity and 12 bolts are everywhere... Odd!!
-- Edited by 67Poncho on Tuesday 5th of October 2010 09:25:06 PM
i leave it alone if i was you. when i was having all the trouble with the rear end noise ( in the car ) i had 3:36 changed to 3:08 eights the guy told me a little on slow on take off not even noticable but saving on gas. leave it alone if you need a good installer let me know
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