View Full Version : Chevy tranny swap.

08-19-2004, 09:41 PM
I have a 67 C30 with a four speed manual [behind a 283] and 5.10 gears. Does anybody know if the newer five speed overdrives will bolt up to these bellhousing and if so what tranny and year? I would sure like to drop my cruise RPM.

Thanks , Tom

08-19-2004, 09:53 PM
hmmm,let me check into that.i'm building a checy shorty right now and should dig some info for you. do have a question..why such a heavy gearing 5.10?

08-19-2004, 11:23 PM
Tom, It's not really economically feasible to perform a swap like you are suggesting.. It is far from being a "bolt in" swap.. No, modern, "production" overdrive 5 speed trannys will not bolt up to the berllhousing, the tranny in your truck is supported by the bellhousing, for a 5 speed you'd need to swap in a crossmember, the list of problems goes on.... Did you mean 4.10 gears??? the lowest I've seen even on an oldy like that is maybe 4.88's.. Either way, if you we're to go through the considerable expense/major hassle of a tranny swap, or even a rear gear swap to a more "highway" friendly ratio like 3.73's, you will very likely be dissapointed with the truck's performance. The little 283 needs a deep gear like 4.10's to really pull with any authority at all..

I'm not trying to bust your idea/ sound negative, I'm just trying to clue you in... A much more economical/ higher performance swap with 0 fabrication would be:

Swap the 283 for a 96-00 350 vortec engine equiped with an edelbrock performer and a good Quadrajet carb ( you need the intake to carburate one of these engines )

If indeed the truck has gears that even approach 4.56 swap the gears to 4.10-3.73 , or alternately, swap in arearend froma later model c-30 with the appropriate gears, as the rear end in your truck is difficult to find a ring and pinion for.. PM me if you need details/explanations about any of this.. God bless

08-20-2004, 08:57 AM
I had a 69 chevy c 20 with those gears , Dishboy what I did was I found 19.5 rims and tires and used them, the large round fender wells allowed this with out a lift kit. The tires measured 36 inches tall but were normal width.

08-20-2004, 09:46 AM
Thanks for your imput guys,

Camland; this was originally a 6 cylinder truck that a mechanic friend of mine owned and had already made the V-8 conversion. His son needed a motor so he robbed the 327 and sold me the truck. I am not 100% sure on the gear ratio, I am only going by what he told me. He had rebuilt the rear so I am figureing he is right.

txlawnking; you are probably right on the expense and hassle if there is no easy swap. The gearing on the truck works great around town with the 283 [headers, intake , mild cam] so I am hesitant to swap gears. I just moved and now have a commute 35 miles round trip and the gas mileage at 55 is only 10.5. I think I will see if I can put a slower secondary spring in the Holley 600 square bore vacuum carb to keep it out of the secondary's at cruise to see if I can bump the mileage a couple MPG.

A 350 with a taller gear would be a better choice, I agree. I think a quadrajet is a great carb for a car, but for pulling weight the primaries are two small so you are always in the secondaries resulting in terrible gas mileage. I swapped my quadrajet out on my 75 C-30 [has a 350] for the Holley and power and gas mileage went up.

Would one of the later four speed auto trannies be a easier swap?

Mdirrigation; great idea on the wheels, if I swap to a 350 that would be a good way to go if I can find that wheel in the dually small lug bolt pattern.

Thanks everybody,


08-20-2004, 10:56 AM
Tom, no a later model tranny wouldn't be an easy swap.. Look under the bellhousing.. that is where the tranny " mounts" , If my memory serves me correct.. In order to swap just about anything, you will need to remove that crossmember, ( it's riveted in, NO fun to remove ) and get a cross member from an auto.. If you go 5 speed, in addition to the $$$ tranny, you will need to engineeer a hydraulic clutch, as those tranny's use one.. with an auto, you still need the cross member. All of these thing add up quick. Thereason a q-jet did not get the mileage& power on your motor is a combo of two things. 1- Not properly jetted 2- too weak a motor for the weight you are carrying.

Unfortunately there is no "cheap fix" for your prob.. If you put a heavier spring in the Holley, then your around town performance will suffer. The 283 ( with mods ) makes it's power at higher r's than a 350 would.. Lowering the highway R's may take the engine out of it's peak efficiency.. I'm VERY surprised you're getting 10.5mpg...

For the $$$ you can usually find a low mile vortec motor for @ $650-850 depending on your market, swap in a 14 bolt from a later pick up or cab chassis ( measure twice ) for around $250-450.... Is the truck really worth all of this hassle? I doubt it, unless it's mint. I believe you'll probly be better off financially if you find a later model truck that suits your needs without a bunch of mods. It is cheaper to buy a truck that suits you're needs than to modify one that doesn't.. Don't forget to include your time involved with all of this swapping...

I understand, I'm a modifier at heart as well. I just learned that I don't like to be working on WORK vehicles.. I'v espent many hours and lots of $$$$$ doing thing like you are contemplating. Every time I was done, I added up the bills ( not to mention my time ) and realised I would have been better off just getting something ready to rock n roll' without any Labor...

If you really wanna do swaps and such, PM me and and I will help you any way I can....