The Quest For Overdrive . . .

[Frankenchevy]

How close are your tires to needing replacement?

Maybe a 465 and a slightly taller tire? Essentially an OD with the taller tire and a stronger trans with more gear variety for how you are using it. Whether it’s 1:1 or .75, it’s still relative to final ratio (tire and rear gear).

Though there are obvious downsides to a taller tire, as well.

 

[DoubleDingo]

I have a couple minutes to elaborate on my previous posts.

3.55 gears, leave it alone. Seriously, leave it alone, it is such a great highway gear. You don't need overdrive with the 3.55 gear, you need better take-off gear, like what you'd get from an sm420 and sm465. I know this from years of driving around in a c20 that had a 350/sm420/3.54 setup. It was by far the funnest vehicle to drive, and got 14-16 mpgs at 2600 rpms.

If you don't swap in better 4.10 or 4.56 gears, your overdrive is useless, you'll be in direct almost all of the time.

If it were me and my money, I would spend it on an sm420 or sm465 and a high hump for the cab and run the piss out that truck with that setup.

You have the 3 speed. Unless you have the good first gear 3 speed, you are slipping the clutch a lot on take off. The sm420 and sm465 would eliminate that slippage.

 

[jjester6000]

How close are your tires to needing replacement?

Maybe a 465 and a slightly taller tire? Essentially an OD with the taller tire and a stronger trans with more gear variety for how you are using it. Whether it’s 1:1 or .75, it’s still relative to final ratio (tire and rear gear).

Though there are obvious downsides to a taller tire, as well.

I'm already running a 31 inch tire, and I was thinking about a SM465.

I also have Muncie M21 laying around that probably needs gone through (I bought it a few years ago thinking it was a Saginaw 4 Speed).

To install that all I would need are a some new shift rods since my shifter came from a Saginaw 4 speed (I could probably modify the existing ones to work).

 

[bucket]

Idk anything about T5s other than what I’ve read/heard.
But the NV3500, I’ve put through the paces as daily/towing/hauling. (Like towing 8-10klbs x country in the summer) Had over 200k on one and 100k on another as daily/commuter/work trucks/ the occasional heel toe clutch dump smoky burnout and never had an issue. Certainly never broke either.
But any old 25-40 year old used pick r pull transmission is suspect for condition and longevity until it’s known.

The T5 is not nearly as durable as the NV3500, or even the HM290 predecessor. Many have been broken behing a very mild small block in the 3rd gen F-body.

 

[DoubleDingo]

I'm already running a 31 inch tire, and I was thinking about a SM465.

I also have Muncie M21 laying around that probably needs gone through (I bought it a few years ago thinking it was a Saginaw 4 Speed).

To install that all I would need are a some new shift rods since my shifter came from a Saginaw 4 speed (I could probably modify the existing ones to work).

The 4 speed won't help your take off clutch slippage. The sm465 is the better choice

 

[jjester6000]

The 4 speed won't help your take off clutch slippage. The sm465 is the better choice

Yeah, but the M21 would hold up pretty well in this application, and it would be little more fun to drive.

 

[idahovette]

I don't think 1st gear is deep enough for your application in the M21

 

[DoubleDingo]

Yeah, but the M21 would hold up pretty well in this application, and it would be little more fun to drive.

With the M21 4 speed's 1st gear it would only be an extra shift to get to direct. The M21 and M22 were in vehicles with 4.10 gears. Fun as heck banging thru the gears but high revs. The sm465 is your best choice with 3.55.

I don't think 1st gear is deep enough for your application in the M21

^^^^^^^^^THIS^^^^^^^^^

 

[mcarlo86]

@DoubleDingo and @idahovette are both correct. Leave it alone or if anything, go to a sm465 if you want more durability. That 3 speed will hold up well enough as long as you aren't doing dumb stuff like clutch dumps or power hopping the rear end in deep snow. Do you have a floor shifter on it or still using the column shift? They do shift a lot nicer than a 465 with a floor shift.

 

[ByrdDog]

I had a 91 K1500 with the NV3500. The TBI 350 lasted over 300k. The trans had to be rebuilt twice in that time. Completely stock motor.

 

[jjester6000]

I had a 91 K1500 with the NV3500. The TBI 350 lasted over 300k. The trans had to be rebuilt twice in that time. Completely stock motor.

I got a '98 Suburban and an '01 Blazer both with NV3500's swapped into them, and I gotta say that I'm not the biggest fan, but they aren't too bad.

Both of them probably need rebuilt (Input shaft bearing noise, bad syncro's, exc.) but I've still managed put a combined 50K on the two of them in about 3 years (They were both unknown condition used ones when I put them in).

And that was a hard 50k at that . . .
(You can see some of the abuse in this video . . .)

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In that same amount of miles my Suburban went through 3 4L60E's (Mostly because I had two seperate guys off craigslist rebuild the original 300,000 mile one twice).

 

[jjester6000]

@DoubleDingo and @idahovette are both correct. Leave it alone or if anything, go to a sm465 if you want more durability. That 3 speed will hold up well enough as long as you aren't doing dumb stuff like clutch dumps or power hopping the rear end in deep snow. Do you have a floor shifter on it or still using the column shift? They do shift a lot nicer than a 465 with a floor shift.

Yeah, I put a floor shifter in it years ago.

I've driven a few SM465's and it's not really the type of driving experience I'm looking for in this truck.

I might just put the whole Overdrive thing on the backburner and tear apart the M21 since it's as close to a direct swap as you can get.

Maybe later I'll regear the rear end and at the same time I find an OD transmission.

 

[DoubleDingo]

I guess I either had phenomenal sm420 and sm465 transmissions, or I am dumb as stump. All my trucks shifted great. Not close ratio great, but definitely not so badly that I'd rule out the option. Not bagging on you @jjester6000

 

[bucket]

I guess I either had phenomenal sm420 and sm465 transmissions, or I am dumb as stump. All my trucks shifted great. Not close ratio great, but definitely not so badly that I'd rule out the option. Not bagging on you @jjester6000

Out of curiosity, what other manual transmissions have you owned?

 

[DoubleDingo]

Out of curiosity, what other manual transmissions have you owned?

Owned: Saginaw 4 speed, Muncie 4 speed, Saginaw 3 speed, Saginaw 3 speed with borg Warner overdrive, sm420, sm465, np435, subaru 5 speed 5mt.

Driven all of the above plus dump trucks with whatever transmission they had, jeep xj 5 speeds, so yeah, heavy duty stuff so I know nothing sporty.