1st post - 4 spd to 5 spd conversion on a '75 truck

[dudevato]

   I've had a '77 Celica with the 20r / 5 speed for 18 years, 'could not have been a better car.
   I recently got a '75 2 wheel drive pickup with the 20r & a 4 speed. It has a chassis mounted fiberglass camper (Chinook) and when the interior is all put back in will weigh in at the recommended max. weight of 4,000 lbs.
  I'm interested in having the rpm's a bit lower at highway speeds, now about 3,400 at 60 mph I think. So I'm thinking of a 5 speed, all I've read on line shows them to have a .85 OD in 5th. This sounds great. I'm aware I might not /wont be able to climb hills in 5th. This is fine, maybe I only use the top gear on the flat or going a bit down hill.  What I am concerned with is that I've read more than once about the Toyota 5 speeds not holding up, that they have bearing problems, or maybe tail shaft design flaws.  I almost find this hard to believe, thinking God had a large part in designing Toyota stuff.  I'd like to hear any and all input on the subject. I've also heard the 4 speed I have is Very Rugged.  I'd like to think a 5 speed is available that given care and not abused will give me a few hundred thousand miles of perfect reliability.  Is there a model # of trans that I'm after? I've seen reference to W series trans, '55 & 56 I think.  Thankyou for all your knowledge and typing.  I'm in southern calif, 60 miles north of Los Angeles

[79coyotefrg]

the ultimate 2wd transmission would be the R154, but they are very expensive. you might also look at the w55.   thats what was in the 2wd pickup I had at one time.

what goes bad usually is the input gear

[79coyotefrg]

what 4 speed do you have??

[kneedownnate]

You can find that style truck with a 5 speed (should be a w50 75-78) and swap it over, or swap over a w55 from a later pickup too.  I had an 81 2wd toy that came with a 4 speed and swapped in an 81 celica 5 speed, but 1st gear is taller in the celica tranny and I had to fab my own mount and mod the floor to get the shifter in.

As glen said, you can source an r154 from a later model supra, but again that'll have a taller 1st gear and I think you'll need an r151 bellhousing, which will be hard and expensive to find.