i just bought a 4 speed from a guy, it is in need of a few things, nothing major, clutch and throw out bearing. got it for a cool $80, i thought that was cheap enough. My question is: the guy told me that it is "an overdrive 4 speed" which i have never heard of. i'm new at this though, so there are a LOT of things i've never heard of. the trans came out of an early 80s chevy pickup. it looks the same as any 4 speed i've ever seen, but the guy swore up and down that it was an overdrive 4th gear. Any ideas, or was he just confused?
I know ford made them, 4th gear is o/d, kinda like a 3speed with a built in o/d. The fords were not all that strong
i think this is just a generic saginaw out of a chevy, that had a very confused previous owner. could anyone explain to me the math i need to figure my RPM at 70 based on engine-trans-differential gear-tire size? I'm just not sure what kind of RPM this thing will be turning down the highway, and its gonna be the daily driver, (too broke for two cars!). thanks
I think Chevy used a variant of the 833 overdrive trans in some vehicles. It would be VERY easy to tell if it is an overdrive trans. Put a mark on the input and output shafts. Put it in 4th gear. Turn the input shaft one rotation. If the output shaft turns a bit more than one rotation it's an overdrive. If not, the marks will still line up after one rotation.
I'd suggest five rotations....depending on what you market the shafts with, one rotation may not be as obvious as you might think. dj
Davey I don't remember the equation off the top of my head. Someplace I have a calculater for that I'll look for it this afternoon and see if I can e-mail it to you. If you got a sag your final drive is going to be 1:1. You already know that and 80 dollars is not too much to give for one these days. A good tradoff for a light streeter is a 3.2-3.5 gear with a 28-30" tire. You will be cruising in the 2500-3000 range and still have a pretty snappy hole shot.
right on, once i find the final drive ratio of the trans. then how do i go about finding roughly what the RPM will be at highway speed?
GM definitely put O.D. trans in some of their pickups in the 80's. Not sure of the make of them but have driven them. Easy enough to check if it is an overdrive or not. Put it in high and turn the input shaft. If the output shaft turns the same it is not an O.D. If the output shaft turns more than one turn for one turn on the input it is an O.D.
Many manufacturers made them, apparently. The overdrive replaces 3rd gear, and the 3rd-4th shift arm is reversed, so you get direct drive in 3rd.
the rear end has 3.73 gears with 31" firestone bias ply tires. is it gonna be something around the same mark (2500-3000) with the slightly taller tire, and more gear?
http://www.bgsoflex.com/cgi-bin/rpm....0&tdiam=31&mode=Engine_RPM&rpm=2500.0&mph=70 this thing look correct to you????
chevy and gmc used a mopar style 833a as stated before. they came in 81-87 trucks only . no cars. 81-84 have the same bolt pattern as a munce or other gm 4 speeds. the 85-87 had half gm on passenger side of trans and mopar bolt pattern on the driverside. this was because the way the trans is shaped and getting the bolts in on the driverside. if you have the later 85-87 trans you will need the truck bellhousing that went with it. they came in hydrolic and mechanical clutch set ups. i hope you got the factory shifter with it because the are spacific the the trans only. the were factory hurst . if you have any more questions pm me . i really like these transmissions and i have 6 as spares . i buy them up when i can. very good transmission. hopld up good top abuse.
You should be fine. 3.73 gear is what was the gear of choice for dailey drivers weekend warriors for a long time. My calculater is on a disc that I haven't located since we moved my office. This will guve me opportunity to actually find it. I can give you real numbers when I do but you should be in that range with that gear. That will also be a good gear if it turns out that your tranny is an OD. The mistake that most of the fellas make is try to gear to high then their engine is lugging around 90% of the time and their mileage goes straight down the tube as well as it isn't good for the engine. Here is an example, the raven has a 5 speed in his AD truck with a 3.73 gear and tallish tires. @ highway speed he is turning around 2000-2200. It worked fine when he had the 235 in the truck it ran good at low RPM. Now he has a small bock that doesn't start climbing up on the cam until around 2800 to 3000. he can't use overdrive until he hits around 80-90 MPH. The engine will still pull it but his fuel mileage goes down the tubes he gets better mileage in 4th @ 65 then in 5th. Go figure. That looks pretty close. GM most likely would not have used a Hurst shiter on a 4 speed OD tranny. I have been going on assumption also. Maybe better when we get a chance to see the numbers or a picture or both.
well, that is interesting, the tranny did come with all parts needed, clutch is mechanical, and it did come with a hurst shifter. is that specific to the 833a trans? it is so coated with the red clay/dirt that i haven't actually seen a number or name on it. i had just assumed it was a sag. it did come with the bellhousing too. not sure of the year, how can i tell?
look at the bolt pattern on the trans. does it look like the standard sag trans> of on the drives side do the bolts go streight up and down. earily 81-84 trucks are the same as sag. also there is a vin on the trans but you will have to clean it up very good to find it. it is back by were the maine trans case and tail shaft bolt together. i have one of these in and 86 chevy truck . it had a stock 305 with 3.73 gears and 28" tall tires. it would get 21 mpg on the highway. these transmissions have justabout the same gear ratio as a 700r4
i will clean it and get pics on my lunch break. also i will try to get the numbers posted so you can school me on them too! thanks a bunch guys!
he didnt say a brand, and i just thought that saginaw was the standard for GM 4-speeds. if you have any usable input, i'd be glad to hear it. like i said in an earlier post, i'm new to this stuff, so there is a lot of stuff i dont know about.
Its a GM new process A-833 RPO code MY6...google it. I have one in my Bel air, love it, but the synchros are going... Same gear ratios as a 700r, but as a standard.
That is basically a Mopar 4 speed. The OD replaces the traditional 3rd gear with an OD gear. The internal shift pattern is 1,2,4,3 but the shift lever is changed so the shifter still has a 1,2,3,4 pattern.
In response to the first gas crisis in the 1970s, both Ford and Chrysler modified their existing 4spd manual transmissions to turn them into OD transmissions (the Chevy truck trans is a Chrysler-sourced trans). In both cases, THIRD gear was replaced with an OD gearset. The 3-4 shift arm was flipped over so the formerly fourth 1:1 gear set became third and the new OD gear set (in the former third gear position) became fourth.
Well worth the $80.00 if it's not ground up. My cousin picked one up and put it behind the 235 in his '58 Chevy pickup.
with my truck sitting as low as it is and with the channeled cab, i'm not sure i can make the clutch linkage work for the mech. clutch. would it be stupid/extremely hard, to convert it to a hydraulic clutch? would i be able to use the same bell housing?
The trans in the picture is a new process, third and forth lever is looking down which is right for it. Need to make sure it has a chev bolt pattern unlless you have the right bell housing because most of the steel case ones had a mopar pattern. Most of the steel cases were behind chevy diesels.
I have this trans in my mid 60's Chevy pick up. Works fine between a 300 HP 350 & a 4:10 rear. I'm not a drag racer but run @ 80 on the highway. Here's a few more links on these trans. Good pictures. Enjoy. http://67-72chevytrucks.com/vboard/showthread.php?p=3895102 http://www.classicjunkyard.com/new_process_a833.htm http://www.elcaminocentral.com/showthread.php?t=30838&highlight=A833+overdrive
Chevy trucks came with a hydraulic clutch starting in (I think) 1985, so you could do it with stock parts.
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