The Stovebolt Site Forums The Shop Area Engine Shop Why a T5 over 3.55 gears?

We should have a new section titled: 'Beating a Dead Horse'...

For the moment, lets add to the numerous T5 threads we had in the recent years, shall we?

I must say the (relative) strenght of the Canadian dollar makes the 3.55 gear set a tempting proposition, these days... A 100$ saving over last year!

Why a T5 over 3.55 gears?

Following market prices, I dont see how I could do the T5 swap under 500$CDN? Unless I come across supercheap, good quality parts?

I dont have ALL the numbers but, all in all, wouldnt there be a minimal difference in highway usabilty between the T5/Blazer diff. combo and the 3.55 gears?

Maybe this has been compared in another thread but a search revealed no such 'Comparative Analysis'.

Whizzerick

The only thing I can add is that I now have a blazer rear end(2:73) and s-10 five speed in my 52, previous I had the patricks 3:55, his sagnaw modifed 4 speed transmission,, this lasted for over 5yrs, went out so I had the torque tube and drive train replace with the conversion,,,,,results is twice the gas mileage, from 10 to 21 on the hi-way,, twice less strain on the engine as the 3:55 would turn 3,000 or better at 60 where as now it is about 1650.. I did have mine done by a local shop as I did not have the tools or space to do so,,,, to me the change was well worth it,,,although the 3:55 change will boost your speed it is still running a pretty high rpm at 60 plus,,, just my 2 cents,, I have had both, Patricks is a good set up but I sill prefer the s-10 blazer conversion,,, not cheap if you have some one else do it, but worth ever cent to me,,I think webeold would agree also.....Fred

Woa! Impressive numbers...

You still have a four speed and only three usually work. You still have ? 50++ old bearings in your old rear end. You still have small rear brakes. You still have small universal joynts and a CLOSED driveline. It's a toss up if you have someone set up the 3.55 ring/pinion. I don't think I'd go w/ a 2.73 blazer rear end but if you live in the flatlands of america that's not a problem. Go to the hill country w/ a 2.73 (did NOT know blazers came w/ 2.73's) and you'll only use the first three gears of a T5.
Me, I'm only want to do it once, the first time, don't have the time nor $$ to rip it all out and do it again.
BUT if you have an sm420, the jeepers would want to buy it, and you can recoup $$$.
see
http://www.stovebolt.com/bboard/cgi-bin//ultimatebb.cgi?ubb=get_topic;f=2;t=010333;p=1#000000

but a 2.73 isn't listed in the above link.
but i do have a copy. in 5th you'de be running 1600 rpm @ about 60-61mph. If you come to a small hill you're back into 4th :confused:
Something sure doesn't sound right, but to each their own. It all depends on the deals one makes and where the parts come from. See what fits you best. That's why I did the math and posted it for all to see. mid to late 70's GM 10 & 12 bolt have 6 lugs.
good luck and have fun! http://www.smokemup.com/auto_math/mph_range2.php

28 inch tires - T5 Borg Warner
Tire Diameter 1: 28.0 inches
Rear Gear Ratio 1: 2.75:1
MPH
RPM 1st 2nd 3rd 4th 5th 6th
1000 10 15 22 29 39 0
1500 15 22 33 44 59 0
2000 20 30 43 58 79 0
2500 25 37 54 73 98 0
3000 30 45 65 87 118 0
3500 35 52 76 102 138 0
4000 39 60 87 116 157 0
4500 44 67 98 131 177 0
5000 49 75 109 145 196 0
5500 54 82 119 160 216 0
6000 59 90 130 174 236 0
6500 64 97 141 189 255 0
7000 69 105 152 204 275 0
7500 74 112 163 218 295 0
8000 79 120 174 233 314 0


Ps joker
i like your sign off...

C. truck, you are correct, if you did a lot of towing or hill driving you would probably be better off with a lower gear, 3:73 or in between,2:73 works well for me here in my area, I did lose a little off launch but not that much,, the number is correct on mine,, at 60 plus the rpm is around 1650,,, with the 3:55 ring pinion and torque tube is was 3,000 and above...webeold has similar set up with 2:73 in his 54 and he is happy with it,, to each their own, I am happy with mine and would put it up against any other 235 on the hi-way, regardless of what rear end they had, I will stay with them....you are correct that at 60 plus and you come to a hill you may drop down into fourth,, with other gearing you may not have too, no problem for me to get use to,, just gear it down and then up..Fred

joker - but you have 5 lug wheels all the way around, right? or no?

-W

I have 6 lugs all around, one reason for the blazer rear end,, they have 6 lugs....I wanted to keep mine so went that route...........Fred

I AM HAPPY HAPPY HAPPY!!!!!!!!!!! i have 235-70-15s on the rear and it does very well for me. as good off the line in city traffic as any thing that is out there with me, i keep up nicely. i will test its towing ability later in the year. i have small hills in my aarea and will try to find some steep ones aafter the weather gets better. ron ( we b old )

A few years ago, I thought long and hard about what to do to make my truck a better highway driver. At the same time, I didn't want to give up the advantages my sm420 has. In particaular, the granny gear and the fact that driving around town in 3rd with a 3:90 rear is the next best thing to having an automatic. So... I've been saving my money for a couple of years, took a second job, aggravated the sheriff, and bought a gear vendors overdrive. I just got it last week and am in the process of pulling and rebuilding the sm420 before I marry it to the O.D. I believe that will give me the best of both worlds. 4th over will be the equivilant of having a 3:09 rear. At 3k, it has put me in the poor house (and the doghouse) for a while, but I think it will be worth it. I've sacrificed nothing as far as low end power, and living in the land of steep hills and boat ramps, that makes me happy.

joker, what caused your rear-end to go out ? Seems like it should have lasted longer than five years.

well the patricks ring pinion was installed in orginal pumkin,,most of the problem was with the u-joints in the torque tube,,they broke, I replaced myself. which was a problem, lasted 2 days, and I had a grind going into 4th gear for many yrs so I just decided to replace...dont know for sure th at the rear-end itself was bad...I had driven the truck 5 yrs at the time but the set up in it had been there for a total of 10....dont get me wrong, it was a quick son of a gun and shift patteren was short with the modified sagnaw from patricks,,I like it better now because I believe I have less strain on the engine...thanks for the response..Fred

For me, it's a chance to get rid of the closed drive line, something that I have never been comfortable with. I've always been concerned with the transmission oil leaking back to the rear axle and the general "leaking" that a closed drive line brings with it. I've lost one transmission by the oil going down the torque tube to the rear axle.

In addition, it offers more than 3:55 gears, it offers more gear combinations for different situations that can be presented.

Finally, I like the whole idea of it!

It's not "beating a dead horse" as far as I am concerned, but a matter of making our tucks better! If you want to get right down to it, any of these ideas exchanged here tend to be beaten to death, but ideas and the discussion of them is one of the things that I thought The Stovebolt Site is about. Did I miss something?

Joe

no but I did,,,,,,,,,,,,,,,,,,,,,just let me have that 37 of yours Fred

Does the T5 swap require throwing the column shifter in the bush? I would think switching to floor shift results in the loss of the middle passenger. To me that's more important than the gas mileage. Can somebody sit in the middle of an AD cab with a floor shifter?

Just to make things interesting...
I have the 4.57's in my 3/4 ton. I found one of the old GM 3 speed w/ OD trannies. With the OD engaged, it will give me a final drive ratio of 3.43:1. So, with 31" tires, I'll be just over 2200 rpm at 60mph, 2600rpm at 70mph. It seems to me that this will be right in the powerband of the engine. Plus, I still have the low gearing to be able to pull a house over.

I.B. - don't think you'd be able to find a column shift for a 4 or 5 speed in an AD, but any young buck can tell ya that a floor shift is by far the best when yer lady is sittin in the middle - ya might have a problem w/ 3 overweight guys, but in an AD that'd be tight even w/ a column shift!

Bill

I.B. mine had floor shift previous so I did not have the column issue,,yes ,, yes, you can still have a passenger close to you, sort of interesting at times............

Thanks for the info guys. If I'm not by myself I have the daughter next to me and let the wife and son argue over the window seat when we all go for a ride. I'll keep my column shift for sure. Sounds like Patrick's gearset is my best choice.

and just how many of those GM 3 speed w/ OD trannies are around?? and if it goes 'south' where do you find bits to fix it. Don't get us T5 types wrong Southtowns27, that sounds like a very sweet running gear set up. In my case Caroline wants to drive her truck and there is no room for me in the middle @ 6-4.
I can still reach her thigh :p

Ps Bill, Your truck is looking pretty sweet!

Jim, there's a fair number of them around if ya look enuff - there was a listing on e-bay just recently, guy had like 14 of'em up - the trans itself is the same as any 3spd, the OD tail should last a good while if ya don't abuse it, the only scarce bit is the solenoid - I've got 2 right now, but I'm gonna use an NPA833 [OD 4th] in one truck, the OD's in others

Bill