The Stovebolt Site Forums The Shop Area Driveline Tranny swap in 58GMC

I can get a 96 s10 5spd tranny.How hard would it be to swap out?Modify?What would cost be to rebuild my original 3spd?

More info is needed.

Which motor? 270? 336? other?
what size pickup? 1/2 ton? 3/4 ton? 1 ton?
What rear gears? GMC 1/2 tons typically had a 3.08:1 rear ratio. This ratio is great for economy, but horrible for an overdrive transmission.

Other transmissions are a near drop in such as a saginaw 4 speed, muncie 4 speed, warner t10, etc. Most of these conversions will require cutting a hole in the floor.

Most importantly, how are you planning to use your truck?
John

I have a 58GMC 1/2ton 270 engine.Rearend not sure but betting original.Just want to enjoy cruising-trying to make more roadworthy!Grinds going into third.
3rd owner all original but paint<--

You likely have the 3.08 rearend. I would stay away from overdrive transmissions with this rearend. As a quick check... Is your rearend 6 lugs? What shape is the rear cover in the differential? Round, or sort of octagonal?

A 4 speed would be the way to go. You have many to chose from that are a near drop in.

6lugs&sorta octagon-yes.How can I identify what I currently have?Will a Borg&wagner drop in?What about a 96 s10 5spd tranny?In this one horse town they want WAY 2 much to rebuild the tranny.Close to a thousand dollars!there is a place about 2hrs from here that might do it for around 5/600 ;my 3spd.That kinda money<-- wanted to see if I had other/better options.

ok, you have the spicer 45 rearend. The available ratios for that rear are 3.08 or 3.92. The 3 speed trucks came with 3.08 rear gears.

The T5 transmission will bolt up without too much trouble, but 5th gear will be useless. Craigslist and ebay are your friends.

You should be able to get a good used transmission for less than $300.

Any reccommendation on a tranny swap?

I used a cast iron T10 behind my 270 in my first 59 gmc. Seemed to work pretty well. An sm420 wouldn't be a bad choice either. That would be the stock granny low transmission that was available for these trucks. You would need to put a carrier bearing and a 2 piece driveshaft for the sm420 to work.

Saginaw 4 speeds, muncie 4 speeds including the m21 and m22 will all bolt up to your bellhousing. Some may require a new clutch as the input splines may vary.

I didn't have to cut the driveline to put the t10 in, but I may have had to change the slip yoke on the front of the driveshaft. That was 15 years ago, so I don't remember all the details.

My current 59 gmc 1/2 ton longbed has a 59 pontiac v8 in it with a NV4500 5 speed. The original rearend was replaced by a previous owner with a chevy rearend with 3.90 gears. My v8 ate that rear end up so I am now running a 9 inch with 3.70 posi gears.

Anyway, Overdrive transmissions work well with rear gears in the 3.73-4.56 range. Direct drive transmissions work well with gears in the 2.73- 3.55 range.

3.08 gears are already on the economy side, so I would not go any taller. Taller gears would make it harder to get the truck moving. The 3.08 gears are absolutely useless for towing.

3.90 gears will have better acceleration than 3.08 gears, but freeway speeds won't be as high or comfortable... unless you have an OD transmission. Typically 3.9 gears with OD will give you a final drive of about 2.85:1 which is slightly taller than the 3.08:1 you have now. So 3.90 gears with an OD transmission will give you better acceleration, lower cruising rpms, and higher fuel economy than 3.08 gears with a direct drive transmission.

Use one of the many online gear calculators that give you rpm at any speed and play around with the numbers.

It is also important to take into consideration what the first gear ratio of the different transmissions are, or 2nd gear if you have a granny transmission. Anyway If you take the ratio of first gear and multiply it with the rearend ratio, This gives you a "Launch number". Typically a higher the Launch number would make it easier to start. Example a launch number of 6 will be slower off the line than a launch number of 12.

I know this is a lot of math... but it is important to ballance the performance with the economy desired. You will find that there are many tradeoffs here. If you want economy, you sacrifice acceleration. If you want acceleration, you sacrifice economy. If you want both economy and acceleration, you sacrifice a big chunk of money to get a new transmission and a new rearend.

I hope this information helps. I'm not trying to deflate your enthusiasm. I'm just trying to give yo the tools to chose what is best for you. By the way... I am by no means the expert. Others have ran the s10 transmissions with taller gears than 3.08 and liked the way they performed.

John

Check the gear ratio of that s 10 transmission. Some had a low first gear and not much of an overdive. I'm useing a s 10 tail on a camero T-5 running a 261 with 3.08 and like it. You don't have to run in 5th gear all the time you can down shift or just leave it 4th. If you got why not use it?

THANKS 4 the info--As I stated earlier-I can get a s10 tranny(for around$300)off of C L here.Not wanting to change or upgrade .Just want to be able to enjoy my truck.I just think people want too much $$ to rebuild the tranny.That was the only reason I was curious as to what elese would fit WITHOUT alot of mods.Havent taken it on any outta town trips cuz wasnt comfortable with tranny issue.
How would I check the gear ratio?Is there a way on the net;if I get some numbers off of that transmission?
My rear-end is "either a 3.08 or 3.90"so I guess it would be able to keep up on hwys?Speed limits are 70mph.BUT who says I gotta go THAT fast?I like to "cruise"(not neccesarily fast)&"enjoy my pride&joy"

Not into modifying unless it makes sense.Am pleased with what i have.All original minus tires/rims.Updated the oil,temp,alt gauges;but they fit in original locations.Oh yeah,I did swap out the carb though.Proud to say that I am the 3rd owner&all stock original!

What carb did you have, and what was the replacement?
Thanks.

Check out that 96 trans. It seems they changed from the T-5 around that era. I don-t know what trans they went to. All the trans. after 88 had the electronic speedo & your cable will not hook to it.

What about an 89 Chevy 4x4 4spd tranny?Also has the bell housing.Had attatched to a V-8.Would that matter?Searching for something that I can replace my tranny with when the time comes...

had a zenith &put a rochester on my truck.runs good but no choke.Wished the zenith was in lots better shape though.

Read this article about swapping out&installing a T5 tranny in a classic truck.interesting article.might look into it if i could find a "cheap enuff"trans to use.Or elese I will search for a 3/4 spd that will work.Wanna drive my truck&not be worried.if that means shifting on the floor;so be it.Tranny isnt "dead"yet;but trying to be prepared.