Reproduction Parts for 1916-1964 Chevrolet Passenger Cars & 1918-1987 Chevrolet & GMC Trucks
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My dad and I recently started working on our Chevy and we are struggling with the GMC 270 w/ what we believe is the original 4 speed granny tranny and maybe 4.85+ ratio rear end. We aren’t exactly sure on the rear end ratio.
The truck simply won’t do over 40 mph… can we just change gears in rear end to get some more speed?
We aren’t expecting highway speeds … but we’d like to be able to keep up with cars on side streets… maybe do 50-55mph range.
Any advice?
@jgmtrbb97-2 I'm going to move this to a technical forum to get you a wider audience.
7046 old site posts
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1938 Master Business Coupe
1953 210 Sedan
@jgmtrbb97-2 Mason, Welcome to the forum. The gears in your truck are probably 4.56. The fastest gears available from Chevrolet are 4.11 and can be found in a 3/4 or 1 ton truck through 1972. The most likely candidate will be a truck originally equipped with an automatic transmission. THEY ARE HARD TO FIND. I believe the entire carrier assembly will bolt into your housing. If you can find the gear set and also swap out the transmission to a T-5, you can keep up with traffic. A friend of mine did this to a 1957 3600 with 261 c.i.d. six cylinder engine, and was happy with it but eventually changed to a V8 and automatic transmission. I think he would be happy to share details if you Are interested.
Mike
Many Miles of Happy Motoring
3469 Posts on Old VCCA Chat
Tiny and Mike, thank you. Mike, if your friend could share some details that would be awesome.
@jgmtrbb97-2 Mason, Call or text me at 573 864 6539 or email me at ml.russell1936@gmail.com. I will give you some contact info.
Mike
Many Miles of Happy Motoring
3469 Posts on Old VCCA Chat
Sorry for delayed response… Mike was super helpful.
To make conversion here are what we discussed:
1985-1986 5 speed S10 Transmission … that would keep mechanical speedo
That tranny should provide .75 or .86 in OD
Also make sure tranny has the output yoke with it.
3/4 Ton pumpkin off 72 Chevy… focused on automatic. Should be 4.10
Drive shaft should be changed to 1 piece
Other work or items:
clutch plate … NAPA NCF ND4201
input shaft and bezel on s10 tranny will need to be trimmed down slightly
collar bolts will need trimmed to fit properly.. need to retread the bolts
New hole in floor so shifter can be fit in front of bench seat.. will be about 8” from existing location in floor
Weld existing shifter to the T5 tranny or go modified route
now the challenge is finding the parts…. Car-part.com was one recommendation
Gears are actually 5.14
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