Overdrive option for 340
- Thread starter LJC
- Start date
4L80 a HD TH400 with OD.
Tom T.
Tom T.
There are overdrives from outfits like Gear Vendors, CLICK HERE!
The most economical way is to change the rear end gears.
One concern I see is someone with an engine that has a fair bit of camshaft and they are wanting better mileage, they install an overdrive and are disappointed, the problem being when in overdrive, the engine is operating at a very inefficient rpm.
The most economical way is to change the rear end gears.
One concern I see is someone with an engine that has a fair bit of camshaft and they are wanting better mileage, they install an overdrive and are disappointed, the problem being when in overdrive, the engine is operating at a very inefficient rpm.
oldfoneguy
Active Member
Anything other than a 200-4r is going to need an adapter plate. Those were the last GM Transmissions designed for the BOP bolt pattern.
Here is an adapter plate for the 700R4 CLICK HERE.
oldfoneguy
Active Member
Upgrade your thm 200-4r to grand national spec to eliminate the stator-intermediate drum, governor and clutch pack failures that were so common. Even a base model 2bbl 340 has more power and torque than any 5.0 of the 80's.
LJC
Active Member
Any links where I can get the internal parts ?
oldfoneguy
Active Member
rockauto.com
summitracing.com
jegs.com
You are researching transmission parts for 1987 buick regal or grand national with 3.8 turbocharged engine
summitracing.com
jegs.com
You are researching transmission parts for 1987 buick regal or grand national with 3.8 turbocharged engine
LJC
Active Member
oldfoneguy
Active Member
LJC
Active Member
That's what I was told it was in
oldfoneguy
Active Member
Behold the power of my mind... LoL.
Actually your starting with the best version available of that particular unit. Better clutch packs and the hardened stator. If you're doing the work buy all upgraded parts. With improvements they can be made to handle a surprising amount of power. GET A SEPARATE TRANSMISSION COOLER, I can't stress that enough. These transmissions don't like heat.
Edit: If it is indeed a grand national trans look for code BRF on the casing.
Actually your starting with the best version available of that particular unit. Better clutch packs and the hardened stator. If you're doing the work buy all upgraded parts. With improvements they can be made to handle a surprising amount of power. GET A SEPARATE TRANSMISSION COOLER, I can't stress that enough. These transmissions don't like heat.
Edit: If it is indeed a grand national trans look for code BRF on the casing.
LJC
Active Member
Any suggestions on a converter for the 340 something like 2200 - 2800 stall?
oldfoneguy
Active Member
No sir, sorry.
If you are going to run a high stall converter, anytime you are cruising below the stall rpm, you are building heat and may require a huge transmission cooler. This may not be a good combination with an overdrive which will put your cruise rpm lower than the stall speed. The best way for a higher stall converter to work with overdrive (like newer vehicles) is if it is a lock up converter as used on newer vehicles. Of course some of the older Buick transmissions used a switch pitch converter which had a lower stall for cruising.