Featured Just did a turbo 350 to 700r4 swap out on my '81.

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C3BCDave

C3BCDave

Casual User
C3 British Columbia
Aug 9, 2020
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18
Langley, BC
VetteCoins
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1981 Corvette
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BC
So, just finished this project.
A few adjustments still.
The extra length of the 700r4 requires a driveshaft shortening of 2 1/2 inches.
As well, a new Transmission Crossmember support bracket which I acquired from Bowtie Overdrives in California.
These folk specialize in this and make custom pieces based for certain years. Mine, was specifically made for 80-81.
Highly recommended. Total cost to buy and get shipped up to Vancouver, BC was about 450 bucks.
The job was performed by Andy's ALL TRANSMISSION in Surrey.
Awesome Folks that love their job and what they do.
This was NOT an easy job.
Some adjustments still to be made to iron out the bugs, but all in all, when this is done, I'll have that 4th gear overdrive this car so desperately needs.
As well, the Transmission (Blakehurst Stall Converter 2400-2800) has the added bonus of lock up, which actually works well when cruising at a decent speed.
The reason for the swap was that the previous owner had swapped out the rear diff gears from 2.87 to 3.55.
Unfortunately, top speed was about 95kmh.
The swap out means I can cruise on the hiway with little concern.

Here's To Summer 2020 !! :-D

IMG_20200428_162711912.jpg IMG_20200428_162649592.jpg
 
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I have the same project for my 79. I love the car but it’s really missing the OD. Did you go for a rebuilt 700R4 or simply for a used one straight out of another car ?
.
 
My buddy in Surrey just got his ‘75 Corvette Convertbile converted to a 700R4.
he loves it.
it was done @ Classic & Performance Cars in Delta.

i live in Langley as well. My ‘75 has a 4-sp with 3:55 gears.
it keeps me from speeding on the highway.! Ha ha

graham
 
Ok... given I am not an expert on rear diffs or transmissions but over the year, having a 340 duster 4 speed with 3:73 diff , a 396 SS chevelle 4 speed with 3:55 diff and more recently a 5.3 litre pickup with 4:11 diff, I have never been limited to 95 kph with any of them. Sounds strange to me that 60 mph (95 Kph) is a top speed but what do I know. Is it due to the low (190) HP of the 81 Vette. Someone give me a lesson behind this... for my improved knowledge, if nothing else.
 
Sergio79 said:
I have the same project for my 79. I love the car but it’s really missing the OD. Did you go for a rebuilt 700R4 or simply for a used one straight out of another car ?
.
Click to expand...
The place I had the work done made several calls, but without major shipping charges, couldn't locate a 700r4 close by.
I decided to check out Marketplace on FB. Lo and behold, found one here in Langley, BC. $300. :-D
I had a COMPLETE rebuild done on it.
 
Rruuff Day said:
Ok... given I am not an expert on rear diffs or transmissions but over the year, having a 340 duster 4 speed with 3:73 diff , a 396 SS chevelle 4 speed with 3:55 diff and more recently a 5.3 litre pickup with 4:11 diff, I have never been limited to 95 kph with any of them. Sounds strange to me that 60 mph (95 Kph) is a top speed but what do I know. Is it due to the low (190) HP of the 81 Vette. Someone give me a lesson behind this... for my improved knowledge, if nothing else.
Click to expand...
It's just how the Turbo 350 and the 3.55's turned out. Sure, i could push it to 110kmh, but not for very long...engine was just screaming at that point....
 
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nascar03 said:
My buddy in Surrey just got his ‘75 Corvette Convertbile converted to a 700R4.
he loves it.
it was done @ Classic & Performance Cars in Delta.

i live in Langley as well. My ‘75 has a 4-sp with 3:55 gears.
it keeps me from speeding on the highway.! Ha ha

graham
Click to expand...
This vehicle of mine still needs some tweaking. Although the work is under warranty, maybe I should check that place out...Thanks
 
Ah yes. I misread that the previous owner made the swap....it all makes sense now. I am sure you will be much happier with OD. I am also going through a change (TH400 to T56 Six speed). Two overdrives! Although I am a long way from driving still....Here to fall and getting back to work on the car!

T
 
Hey @Rruuff Day ..... a truck with 4:11s works because the tires are probably 30”+ tires.
Some even run 34” tires.
Same story with some of the older muscle cars of the day.
Back then we all ran G70-15s, then the Sixty-series tires came out in the late ’70s.
By then not too many cars were being offered with anything near 3:73s or higher.
My friend’s ‘63 Vette had 4:11s, but running 70 series tires it was livable on the street.
My ‘75 now runs 25.5” tires with 3:55 gears, no overdrive.. Speed on the highway is limited by
the RPM I wish to run.. 80 MPH is approx 4000 rpm, cruising speed.
I can go 120MPH if I wish to turn beyond 6K rpm...
But that usually doesn’t happen for any length of time. Only long enough to win.!
ha ha

graham
 
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