Need help on transmission choice...

[Shanks]

Hello everyone! I have a 68 chevy with a 250, 3 speed in the floor (moved from column by PO), and 308 rear end. I really am not happy with the 3 speed. I would like to either switch to a 4-speed bulldog (granny gear), or a later model 5 speed.
Any suggestions on which would work out better?

Thanks!

[71K20chevy]

5 speed should equal better gas mileage

[cdowns]

i think the granny 4speed might b a bit better// the 5speed i doubt would b very much of an improvment due to very heavy weight low power of 6cyl and the 308 rear i'd think you'd see no increase in milage probally a decrease if you lucky break even after all that work an unable to really use 4 or 5gears unless goin downhill on a very long streach of road

if i was to do anything with the combo you have i'd change to lower rear gears

[Shanks]

I could change the rear gears, but would not really make a good daily driver. I agree that the granny 4-speed would probably be my best bet. It would at least help me to take off a little easier if needed.
Anyone know where i could find one cheap?

[MARKDTN]

I would look at the 87-96 type 5 speed. It was behind a 4.3 6-cyl. I don't think a granny gear will help much with a driver. Now if you were loaded all the time like a service truck might be different. With a granny gear 4 sp you still only have 3 "useful" gears.

[cdowns]

Originally Posted by MARKDTN

I would look at the 87-96 type 5 speed. It was behind a 4.3 6-cyl. I don't think a granny gear will help much with a driver. Now if you were loaded all the time like a service truck might be different. With a granny gear 4 sp you still only have 3 "useful" gears.

spend the weekend lookin at those 4.3 with 5speeds lets us know the very small percentage if you find any with a 308 rear/// when i looked the vast majority where exuipped with 410 rears so they scould use all 5gears and not just 3

[BAT]

I just posed this same question and I am sticking with the T5. With this option your choices are either find an F-body trans (which should be a WC T5) and drill out the metric mounting holes to 1/2" to bolt to the bell housing, but then you would need an S10 tail housing to move the shifter up (unless you have bucket seats), or install an S10 (NWC) T5 but wont have the beefier gears of the F-Body. you can read more about this HERE

Also, I will have an S10 T5 for sale within the next few weeks.

[MARKDTN]

Not sure why that matters?

NV3500 5-speed ratios:
4
2.32
1.4
1
.73

3-speed ratios:
3.5
1.9
1

With the NV3500 I would have a lower ratio to start with, 2 intermediate ratios, a direct and an overdrive. A granny gear tranny will have like a 7 first gear, 3 something second-about the same as a 3 speed, and then 3rd and (direct) fourth. In my mind, I like the 5 speed for a driver better.

[Shanks]

Thanks for the info!
I am leaning now toward using an s-10 5-speed. Will i need to adjust the length of the driveshaft?

[BAT]

Originally Posted by Shanks

Thanks for the info!
I am leaning now toward using an s-10 5-speed. Will i need to adjust the length of the driveshaft?

Yes, I want to say mine was made about 3" shorter. Also, you will want to be sure to get a tail housing from an '88 or earlier (getting harder to find) because the newer ones have electronic speedo output. Otherwise your choices are a)install an electronic speedo, b) install a Cable-X unit (not optimal IMHO), c) no speedo or d) change over to a mechanical rear housing at a later time.

The PO started a half a$$ed restoration so my truck came with the F body front and S10 rear that had an electronic speedo output. I just paid A LOT of money for a full S10 trans just to get the mechanical rear housing. I will be swapping this out next week (all this for a working OEM speedometer). If you opt for the F-Body trans and S10 rear, you will also need the shifter rod from the S10 in addition to the rear housing.

I have done a lot of research on this and have many references, if you have any specific questions feel free to PM me and I will share whatever I can. Good luck!

BAT

[68gmsee]

Are you looking for more lower end power?

If you looking for better gas mileage, truck already has a 3.08. I'd be concerned about engine stress with overdrive trannies.

[cdowns]

Originally Posted by BAT

Yes, I want to say mine was made about 3" shorter. Also, you will want to be sure to get a tail housing from an '88 or earlier (getting harder to find) because the newer ones have electronic speedo output. Otherwise your choices are a)install an electronic speedo, b) install a Cable-X unit (not optimal IMHO), c) no speedo or d) change over to a mechanical rear housing at a later time.

The PO started a half a$$ed restoration so my truck came with the F body front and S10 rear that had an electronic speedo output. I just paid A LOT of money for a full S10 trans just to get the mechanical rear housing. I will be swapping this out next week (all this for a working OEM speedometer). If you opt for the F-Body trans and S10 rear, you will also need the shifter rod from the S10 in addition to the rear housing.

I have done a lot of research on this and have many references, if you have any specific questions feel free to PM me and I will share whatever I can. Good luck!

BAT

the question i have is::: have you personally in fact ever had a straight 6 with a 5speed and a 308 rearend in a 40 year old truck on the road with milage to show

[MARKDTN]

Originally Posted by cdowns

the question i have is::: have you personally in fact ever had a straight 6 with a 5speed and a 308 rearend in a 40 year old truck on the road with milage to show

If you are asking me if I have-no-I have not personally. I would do a (fuel injected) V8 swap before I would swap the trans. I would (and have) swap to overdrive automatic before a manual trans-for the application listed. I would not use a T5 or a T56 trans in a truck either, but that is me.

All I was trying to do was answer the OP question of would he be better off with a 5-sp or a granny 4-sp for a driver. IMHO a modern 5 speed with overdrive is a better choice than a granny 4-speed for a 1/2 ton 2wd driver truck. The NV3500 should be strong enough, the NV4500 would be even stronger, but not necessary. If he was hauling a lot or going offroad or 4wd then it would be a different answer. The following are the facts-regardless of rear ratio. The NV3500 5 sp has a 4:1 low gear as opposed to the existing 3-sp with 3.5:1. That will give a better start, but not so low as not to use it like a granny gear. The 5-sp then has intermediate gears 2.32:1 and 1.4:1 where the 3 speed only has 1.9:1. That will help on mid range by giving "steps" to keep the engine closer to it's power in the RPM band. Both have a 1:1 gear for primary use. Then the 5sp has a .73 overdrive if you ever get on the highway. I can't see why that is a bad choice?

[cdowns]

spend lots and lots of time lookin at factory 6cyl with overdrives//then try and figure out why they are mostly all equipped with 373 411 rears KNOW WHY??? GM figured that the punny arse 6cyl cant power an overdrive 2ton truck and the inlines are weaker than the 4.3 v6

have seen many people put overdrives in trucks with those hi gears over the years thinkin they will reap great results and they came to find the gas milage and driveability ssuffered dramatly and the hole project was a wasted effort

[BAT]

For me, I am swapping out to a 4.10 gear in the rear. As for gas mileage, considering how much money I have in to this restoration you really think I'm concerned about gas mileage?

[cdowns]

so in other words everybody telling you to goo overdrive noone have done it with a vary hi ratio rear like the poster has and i think even less has it with a 6cylinder??


me i really dont care just tryin to save the original poster of this thread time and money


without a doubt 5speeds are nice but to get the most out of one i'd pay a great deal of attention to how GM offered them for sale and in what configuration they work the most effectivly

IN MY OPINION A SIX WITH A VERY HIGH REAREND AND AN OVERDRIVE TRANNY WILL B A DOGGY that cant even wag its tail

[BAT]

I guess I missed that he was running a 6 cyl... I'm running an SBC.

[69chevy lwb]

i have a 292 with a granny 4 speed im going to run a t5 behind i do have 3.73 rear gears but that motor runs great i wouldnt trade it for a v8 it geats great mileage and i can burn through 3rd if i get after it, it puts my 88 gmc 350 tbi to shame

[Shanks]

Now I'm really confused! LOL
I'm not as much concerned with gas mileage as I am drivability. I find it slightly difficult to take-off on a grade, especially in traffic. I need something with a slightly lower take-off gear, and I thought that the granny 4 speed would then give me a highway gear to boot.

Thanks for all the responses.

[69chevy lwb]

The granny gear is good for taking off slow but its unsyncronized and you can do about 7 mph in it and the rest of the gears will be about the same as your 3 speed both have a 1 to 1 4th gear
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[69GWC]

With that 3.08 rear gear he might be able to use that 1st gear alot more,, I have 3:73s in my truck and that 1st gear is about worthless, I put on a set of 33s (had 31s) and will say 1st gear is more useable now then it was.


I agree that the 5th gear might not be able to be used because of the lower power out put and the 3.08, but if he went to a 3.73 it might be just the ticket. I had a 92 s10 with a 2.8 and 5sp and it had 3.73s and that combo worked real well I thought.
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[69chevy lwb]

Im not sure if the nv3500 was built the same as the nv4500 but the 92-94 gm nv4500 had both a granny gear and and od 5th they also line up with the factory floor shift I would look into that
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[Shanks]

How would the nv4500 line-up with everything else? (motor, drive shaft)
Would it require a high-hump?

[Shanks]

I just recently read a thread by "ta2ed" where he swapped out a 3 speed for a nv3500. He had the same rear gears that I do, with a similar engine. It sounded fairly simple to do. He did mention that the drive shaft would work fine.

Would I have to upgrade anything else though?

[Wrenchbender Ret]

The S-10 T-5 is plenty strong for that 6 cyl. engine. The 1st gear is 4.03 or 3.76 & would be good for taking off from a stop. It will give great driveability with the first 4 gears & the o-drive would only be used for down hill with a tail wind. The nv4500 is an overkill. It is a monster. The NV 3500 requires the use of a hydraulic clutch & would not have provisions for the rear mounts. You would have to remove the crossmember.