H190 swap

[troyt]

Is the diff unit from the 6 lug 620 pickup H190 swappable into the 510 wagon 4 lug H190? Specifically the Ring & Pinion?
Thanks

[jesusno2]

ive been told that a pickup rear end will fit if ya swap the side gears. then you could get a 3.7 diff from a 720 truck and use your 4 lug axles which would make a nice freeway driver with the right 5spd

[troyt]

Thanks. Specifically I'm looking to get the 4.38 R&P from a 620 under my wagon that is going racing. Some type of LSD as well. Anyone do this swap?

[datzenmike]

The truck 4.375 H-190 will drop in if you swap the side gears from the wagon diff into it first. The wagon has 23 spline side gears and the truck 31... or 29 I forget. No the truck axles won't work. The H-190 never came with a factory LSD that I know of. Correction the Roadster did and had the 23 spline side gears... good luck finding one... for under $1,200. Get an aftermarket one. The first truck with one was the WD-21 in '87, beating even Toyota, of course it was the larger H-233.

H-190
520/521 with J13 motor 4.875
'68-'72 521 4.375 *Aluminum case same as Roadster and wagon.
'73-'79 620 truck. All were 4.375 except for the '74 automatic (4.625) and the '79 standard (4.11)
'80-'86 720 2wd and '80-82' 4X4 with ratios of 3.364 (yes) 3.70, 3.889, 4.11, 4.375.
'82-'83 S110 3.70 and 3.889
'80-'84 810/Maxima with 3.364, 3.545, 3.70

[jesusno2]

dang you can get a 3.54 ratio that be great for a DD escpecially in a engine swaped 510 that can pull a taller gear like that. thanks for that info mike im going to start a hunt for one of those.

[datzenmike]

You can also run larger diameter tires too.

I'll assume you have a standard 3.70 rear gear and a stock 4 spd. Going from 3.70 down to a 3.545 gear only drops you by 4.18% in any gear. This translates out to a drop of only 125 engine RPM in fourth at 3,000 RPMs. ( plus some loss of performance)

Installing a dogleg will add an overdrive if 13.6% with a drop of 408 RPMs at 3,000. The car will perform exactly the same as before but have a lower 5th gear cruise RPM on the highway.

The FS5W71B from an '80-'83 non turbo has an overdrive of 25.5% and will drop 765 RPMs shifting into 5th gear from a 3,000 rpm 4th.

This is a hell of an RPM drop, and may be so low the motor may not produce enough power to pull the car along at highway speed against the wind resistance and any slight up-grade. One way around this is to install a higher 3.889 rear from an automatic wagon. In effect lessening the drop of the overdrive... a sort of two steps back, one step forward. Taller gears would give increased performance in the 1st through 4th gears and still a good RPM drop in 5th for mileage.

Just some thoughts.... BTW, high school math wasn't high on my list when I was a teenager, so if you see or find any errors in math or theory please say something.

[spl310]

There is a NOS limited slip with a 3.7 ring and pinion on it now on eBay!

[DryHeat]

I did some research on this a while back and with some help from some very smart people here on the realm it became very obvious that the simplest, least expensive and must robust solution is to do a complete swap with a narrowed Ford 7" or 8".

Replacement parts for the H190 are getting harder and harder to find but the Ford stuff is still readily available and you will have a wide variety of ring / pinion options. There is some fab work to accomlish this but I think it's worth the effort.

[datzenmike]

There is a NOS limited slip with a 3.7 ring and pinion on it now on eBay!

Must be NOS from a Roadster then, as I believe the H-190 was not available with LSD on any other vehicle from the factory. What's it selling for? $1,200-1,500??