manual trans interchangability - Toyota Nation Forum : Toyota Car and Truck Forums

smasheromalley · 06-23-2005, 07:21 AM

I have an 87 cab and chassis dually with a 4speed manual. Is there a rule regarding swapping between 4speed or 5speed, year, driveshaft length, etc. ?

The truck has a very steep gear and Id really like to have an overdrive trans...

smasheromalley · 07-11-2005, 07:01 AM

Has anybody ever swapped a 4speed out for a 5 speed in a 2wd pickup??

tcr22 · 07-11-2005, 12:20 PM

yes i had i friend that did it to a 86 pickup

qsd-dan · 07-12-2005, 04:04 AM

Don't get too excited about the overdrive swap. In my truck it only makes a 400 rpm difference, hardly noticeable in my opinion. I think Toyota did this because of the 55 mph speed limit of the 80's, which happens to be the speed where I get the best gas mileage. Unfortunately, the speed limits have changed since 1997 in California and now I tach out at 3000 rpms doing 70 instead of 2300 at 55 (and I still get ran off the road

)

When I get my trans rebuilt, I'm looking into sending it to marlin and seeing if he can change the gearing of the overdrive so the ratio would be .68 instead of .85. That will get me back into the same rpm range cruising at 70 like I was when doing 55 of the "old days."

smasheromalley · 07-12-2005, 07:16 AM

hmmm, point taken

I guess I wont mess with it then. I dont have a tach in my truck but it sounds like the engine is spinning ass at 65 mph.

Im still getting 24-25 mpg average so I probably shouldnt complain...

Thats my 18foot car hauler hooked up to the back. I pulled 2 cord of firewood out to my moms. Truck was a little short on accelleration but drove 65mph with little effort and the dual wheels made it track smooth and straight as can be

qsd-dan · 07-13-2005, 02:16 AM

There is one more option if you don't mind a little modification. You can put a w58 trans from a Celica in there. It is a stronger trans than any 5-speed trans that the trucks had and has an overdrive ratio of .78. I've heard that it can handle 450 hp so I presume that even your dually wouldn't break it. It will bolt right in, but it sits about 2 inches forward from the original shift lever so you'd have to cut a little sheet metal. It would be up to you if it's worth it or not.

I don't know your tire size, but most duallys have a 4.10 r&p ratio. So lets say you have 195-75-r14 (most common Toyota pickup tire size of that time for 2wd) with 4.10’s and a 1-1 ratio that you have now. That's about 3512 rpms at 65. With the w58 and all of the above specs, but with a .78 final drive, you would be at appox. 2739 rpms at 65. That would be a drastic reduction in rpms!! Probably even pull 30+ mpg

smasheromalley · 07-13-2005, 07:09 AM

Quote:

Originally Posted by qsd-dan

...That's about 3512 rpms at 65....

holy crap, It sounds like it was spinning but I didnt think it would be 3500rpms!

Ive been commuting in this truck which is about 90% expressway. Ill have to look into that celica trans... Thanks for the info!