My Chevy Astro and a couple ideas.

[Isaac Zackary]

Ok. First of all I've been thinking about switching to a Hughes Fuel Miser torque converter. It's supposed to have a lower stall torque than stock (advertised at 1,000 to 1,200 RPM). Has anyone used one of these? Any opinions?

Also I've got this crazy idea to make a homemade hydraulic hybrid system. I was thinking of hooking up a Prince 2500psi 50gpm 80hp hydraulic motor pump (about $300 on Amazon) and a Greer 10 gallon hydraulic accumulator (around $500 used). I'd use a sprocket/chain drive directly connected to the U-joint behind the transmission and gear it so that full RPM would be around 60-65mph. I'd keep around 1250psi in the accumulator. That would mean it would stuck up about 5 gallons by 2500psi I think. Maybe not a big help from coming down from a full 60mph but maybe helpful in 30mph stop and go traffic. I still have to calculate all the torque and acceleration/deceleration.

[Isaac Zackary]

Just a few numbers. 220lb accumulator + 15lb motor pump + about 50lbs of hydraulic fluid + whatever the reservoir, tubing, hoses, valves and frames weigh = something more than 300lbs. It would be able to store or release about 225kW/s of energy in as little as 6 seconds. If I found afford and know where to buy composite accumulators I could double the energy density at about the same weight.

[oil pan 4]

No need to switch to the expensive torque converter if you have a TH700.
GM made torque converters for TH700 diesels that have a stall as low as 900 RPM.

[Frank Lee]

I'd switch to 5 speed manual.

[Isaac Zackary]

Originally Posted by Frank Lee

I'd switch to 5 speed manual.

Yes! That would be awesome! Actually when I was a kid we had a Ford Aerostar with a 5 speed manual. I absolutely loved it! I was wanting a Toyota Previa with a 5 speed. But ironically the 1995 and newer ones, which are super charged and all automatic, get better fuel mileage.

Originally Posted by oil pan 4

No need to switch to the expensive torque converter if you have a TH700.
GM made torque converters for TH700 diesels that have a stall as low as 900 RPM.

I do believe it's a 4L60E transmission, which used to be called the THM700. It supposedly has a different 300mm torque converter, so I'm not sure if the TH700 diesel torque converter would work. I'm also fairly sure that this transmission has a locking torque converter, which feature is I'd like to keep and the Fuel Miser does come with a locking version. I'm not sure if the diesel torque converter would be locking or not.

[cRiPpLe_rOoStEr]

A manual would be nice but, if you or someone that regularly borrows your truck would still feel more comfortable with an automatic, a lower stall torque converter with lockup is a good choice. I'm just not sure if the Diesel torque converter had a lock-up, as the TH700 relied on vacuum as the power source for it...

[oil pan 4]

I don't know that GM made a stock converter that didn't have a lock up.
The diesel converter is locking, that is what I use.

[cRiPpLe_rOoStEr]

So it seems to be the easiest mod. Anyway, is the lock-up in your Suburban vacuum-driven like in the gassers with the earlier 700R4 with lock-up?

[oil pan 4]

It's an 700r4, loosing the vacuum lockup in favor of electronic is one of the 4 "r4" revisions.

[cRiPpLe_rOoStEr]

I still get confused about the naming of those automatic transmissions used by GM in the USDM during the 80's and 90's, since only the TH180, TH125 and the 4L35E were used in local cars here in Brazil, with the 4L60E for the S-10 and Blazer with the Vortec 4300 V6. Other transmissions were outsourced, most notably the ZF 4HP22 and that Aisin 4-speed for transverse-engined FWD cars.