My differential pretty much bit the dust, so I'm looking to get a used rear axle asm to replace mine in my '80 2wd truck and have found a few local ones that may work, although they have slightly taller gearing than my 4.10. I've swapped axle asm's before in other cars, but have a few questions about the 79-83 Toyota 2wd trucks specifically. I tried searching around. but couldn't find anything pertaining to the 2WD's.

1. Are the 2wd rear axle housings all the same length and do they all share the same location and width for the spring perches?

2. Are the pinion flanges the same for all the 4 and 5 speed models for the 1st gens? Does the automatic use a different pinion flange?

3. Are all 79-83 axle shafts from 1/2 ton gas and diesel axles interchangeable between years and swappable left to right and vice versa?

Thanks in advance for any information and help. Trying to get the truck back on the road before next week's planned road trip

 

1. No, rear axle width steadily increased over the years. I belive a pre 79 is 55 inch flange to flange, a 79-83 is like 57, and I never bothered with the later trucks, but they do get wider as well.

2. BYE ran into this problem with the pinion flange when he did his diff. IIRC, there are 12mm bolt pinion flanges, and 14MM flanges. His is an 82 F code 2wd axle.

3. Im pretty sure the axle shafts are the same length (talking side to side). But the backing plate and brakes are side specific and are a PITA to swap.

 

1: Perch width is all the same

2: All pinion flanges share the same centering diameter BUT pre 84 they had a more rectangular pattern with 8mm bolts. 84+ the pattern was more square and used 10mm bolts. Flanges are easy to drill for different patterns. 4 speed, 5 speed or auto it holds true.

3: I'm 99% sure the axle shaft length is different side to side but I do know that shaft length didn't change with fuel type. ie diesel and gas are the same.

If you have a 7.5" diff then any era 7.5" diff will drop right in there but the later stuff will have a different bolt pattern on the flange as I said before. If you have an 8" diff then any 2x or 4x diff will go right in with the same flange issues.

 

You guys are great! Thanks! Now I've just gotta find someone who's selling one

 

Alright, so I'm having trouble locating a 79-83 7.5" diff, so I'm expanding my search to those from 84+ trucks. Can the pinion flanges be swapped between the 80 diff and the 84+ so I can hook up to my stock driveshaft? If not, can the rear yoke from an 84+ truck's driveshaft be swapped onto my stock 80 driveshaft so that I can mate it up with the 84+ diff?

Finally, what is your opinion on going from a 4.10 to 3.73 gearing? I do a lot of highway driving and frequently haul stuff in the bed, so anything gained in mpg is a plus. However, I don't want to drown out the engine with gears that are too tall. The engine/trans are the stock 20R/W50.

Thanks

 

Yes pinion flanges are interchangable. Yes the yoke can be swapped on the driveline if you want to go that route. Personally I'd just turn the driveline 90* and drill another pattern in the existing flange and be done with it.

If you have 4.10's chances are you have an 8" diff. Count the studs holding the diff in the housing. If it is 8 it is a 7.5" if it's 10 it is an 8" diff so that makes it easier and cheaper to find a diff.

If you have a 7.5" diff I have an axle with 3.42's I think it is that I'd take $75 plus the rids for.

 

Ok that's good to know, thanks again!

I counted the studs and I have 10, which would indicate an 8" diff. However, the code on the tag under the hood states F292, which I believe indicates 7.5" ring gear and 4.10 gears. This is confusing....how do I know what I really have?

Edit: I thought all F code rears were 7.5" and all G code were 8"?

 

I'd stick with the data plate info unless you feel the axle was previously swapped.

There's alot of mumbo jumbo regarding the 8" diff and how you can visually tell the difference. The only sure bet is to pull it, measure the ring gear and count how many splines on the axle. Unless ofcourse your the original owner then the data plate under the hood or door jamb will suffice...

 

there's a lot of mumbo jumbo about a lot of things but facts are facts. The smaller diff has 8 mounting studs and the larger has 10 period. One way to tell which I'm not 100% on because I keep forgetting to look is the drain plugs are on opposite sides of the housing too but I'll keep that in the speculative realm till I remember to look tomorrow.

 

Unfortunately, I'm not the original owner, but I'm pretty sure that the axle is original. I got my hands on a 1980 Toyota Pickup FSM and looking at the pics of the diff, they show 10 bolt holes in the diff. So I think it's probably period correct to the truck.

I checked the spline count on the axles and it's 27. Also, looking at the axle from the rear of the truck (fill plug side), the drain plug is at the lower right. I measured the ring gear with my calipers and it's 7.5". Could it be that the 84+ 2WD diffs had 8 studs in the housing, but 79-83 had 10 studs?

 

Its common to find 8" diffs in the earlier trucks. 1 tons and trucks with 4 speeds had them for the most part.

 

Fact 1: My data plate states F372... Fact 2: 27 splined axles... Fact 3: 10 mounting studs... Period.

Here is my mumbo jumbo to visually tell which diff you have... The 7.5" diff's top and bottom studs are dead center @ the 12 & 6 O-clock position. The 8" diff's are the opposite with the studs centered @ the 9 & 3 O-clock positions. Both having 10 mounting studs... This is what I gathered thru experience, so take it with a grain of salt... So far it hasn't failed me yet...

80banana- I do have a spare 7.5" diff in either 3.30 or 3.42 gear set (I forgot which one exactly) ready to go. You'll need to swap out the pinion flange or re-drill it to match your 8mm driveshaft bolts.

 

Yeah, that's how the studs are my housing..."@ the 12 & 6 O-clock position". PM'd you about the diff.