Powerglide swap to ?

[l79m20]

Want to swap my powerglide to better transmission. Cananyone send me in the right direction? Motor is an inline 6/ 250 . What transmission would be the easiest swap and help me get bettergas mileage, by the way the rear end ratio is 3.08 Ideas?

[jtrichard]

Th 350

[jocko]

TH350 should be direct, just make sure it's a TH350 for a chev, not a BOP.
If you want to get better highway rpm - now is the time to do an o/d trans swap to a 700R4 or 2004R. That swap requires some mods, but depending on what you want to use the truck for, might be well worth the slightly extra effort. If you want cheap and simple - TH350.

[Captainfab]

Depending on tire size and how much highway driving you are doing, a TH350 may be what you need with that 3.08 rear gear. If you are doing a lot of highway driving, a 700R4 or a 200 4R may be what you need. However be aware that no one makes a TV cable kit for a I6 engine with a 1Bbl carb. You will have to fabricate something to make it work.

[Lugnutz65]

I'll offer my opinion. With a 3.08 rear gear I would not recommend anything with overdrive unless it was somewhere between 0.85 and 1.00. It would be sluggish in overdrive with a 700R4 which has an OD gear of 0.72ish. I ran a 0.63 OD with my 3.73 rear and 230ci inline 6 to test this idea. It was sluggish in 5th gear.
I'm sure a V8 would do much better because it has more HP.

It's just math. You kinda want your final drive to be just under 2.8 for good RPMs without lugging.
0.63 X 3.73 = 2.35 (too low)
0.72 X 3.08 = 2.22 (even worse)

My OD combo is 0.73 X 3.73 = 2.73 (no lugging with my inline 6).
I recommend TH350.

[LT1 Burb]

Originally Posted by Lugnutz65

I'll offer my opinion. With a 3.08 rear gear I would not recommend anything with overdrive unless it was somewhere between 0.85 and 1.00. It would be sluggish in overdrive with a 700R4 which has an OD gear of 0.72ish. I ran a 0.63 OD with my 3.73 rear and 230ci inline 6 to test this idea. It was sluggish in 5th gear.
I'm sure a V8 would do much better because it has more HP.

It's just math. You kinda want your final drive to be just under 2.8 for good RPMs without lugging.
0.63 X 3.73 = 2.35 (too low)
0.72 X 3.08 = 2.22 (even worse)

My OD combo is 0.73 X 3.73 = 2.73 (no lugging with my inline 6).
I recommend TH350.

I agree, my suburban had the injected 350 in it and it was dog with the 3:08 gears and the 700R4.

[Lugnutz65]

Be aware. The Powerglide and TH350 both have a final drive of 1:1 so swapping to a TH350 will not result in better MPG or lower highway RPMs.

[l79m20]

Thanks everyone! That was the info I was looking for!!

[l79m20]

Any ideas on the th400?

[Lugnutz65]

Originally Posted by l79m20

Any ideas on the th400?

Again, no overdrive but I think you'll like it better than the Powerglide.

[Lokin4AReason]

http://www.drivetrain.com/parts_cata...ic_trans..html

[TJ's Chevy]

You will like the TH350 as it has 3 speeds instead of 2. Better acceleration. Mileage may change as you won't be bogging the engine as much with only 2 gears. Since I like manuals myself, a non-overdrive Richmond 5 speed would be optimum, but they are pricey.

[jocko]

TH400 is not as direct a swap as the TH350. For an I6, Th350 might be a better route/easier route.

[Captainfab]

Behind a I6 I would definitely choose a TH350 over a TH400. Another option for a non-overdrive trans would be the TH350C with the lockup converter. That will drop the rpm's slightly.

[65chevysub]

I went to a TH350 from a P/G and my mileage and power really suck now. I currently have a 283, from a 63 Biscayne, rebuilt in 1996, and 3.73 gears in my suburban. Next year when I get my refund, I'm putting in a 350 motor, and having my gears checked, as something isn't right. My RPM's are way to high with the combo I'm running right now.
Hope you find the right combo for your truck
Merry Christmas

[vin63]

Yep, swapping from a Powerglide to a TH350 or 400 will more than likely yield lower fuel mileage because instead of a 1.76 first gear, you will be spending time at 2.52 or 2.48 for a first gear. And, since they all have a 1:1 final drive, there will be no advantage at freeway speeds. If you do a lot of freeway driving, I would go with a 200R. If your driving is mostly in town/stop and go, I would stick with the Powerglide.

I did a 700R4 conversion for my friend who had a 292 and did a lot of freeway driving. As mentioned before, there will need to be a provision for the TV cable, but it's not very difficult to fabricate. For my friend's 292/700R4 conversion, I fabricated a bracket that used the master cylinder/brake booster mount.