Benzfixen Posted February 28, 2019 Report Share Posted February 28, 2019 Are there any rear differentials that I can swap with mine to make a 3.83 gear or what would any one suggest Quote Link to comment
datzenmike Posted February 28, 2019 Report Share Posted February 28, 2019 I guess you want better RPMs on the highway? First, the L18 isn't that powerful so lowering from 4.375 to 3.889 or 3.7 is a big drop and will make acceleration a bit sluggish. If you have an automatic or expect to carry loads, this will be even worse. It will lower your top speed because the engine won't be making enough power at the lower revs. It may struggle to climb hills or drive into the wind in 4th. If doing this because it sounds like the engine is reeving too high let me assure you it's not a problem. The L18 can run at much higher RPMs all day. This is not going to gain anything for mileage. As to differentials that will fit. The 2wd 720 trucks often used them. Look at the engine tag riveted to the passenger side inner fender under the hood hinge. Lower line where it says TRANS / AXLE............ FS5W71B.......... HF38... 38 stands for 3.889, a 41 would be 4.11, a 37 would be a 3.70 and so on. Pick what you like. You can't use the entire axle just the center differential or 3rd member. 2 Quote Link to comment
2wheel-lee Posted February 28, 2019 Report Share Posted February 28, 2019 An added note to what Mike said, if you're running much smaller size diameter tires than stock, numerically lower gearing may put you back closer to stock speed/RPM. 1 Quote Link to comment
Stoffregen Motorsports Posted February 28, 2019 Report Share Posted February 28, 2019 If you can't find the right used diff, you could always have someone set up a new ring and pinion gear set. 2 Quote Link to comment
datzenmike Posted February 28, 2019 Report Share Posted February 28, 2019 A bit of digging shows he's interested in a set of ]2eDeYe's KA/SR engine brackets. Assume a KA swap in in the works. A 3.889 would probably make much more sense now. 1 1 Quote Link to comment
paradime Posted February 28, 2019 Report Share Posted February 28, 2019 2 hours ago, Stoffregen Motorsports said: If you can't find the right used diff, you could always have someone set up a new ring and pinion gear set. From what I've read 720 trucks and some from the hardbody trucks used the h190 rear differential and the third members are interchangeable. .For instance, you can switch to 89 hardbody rear end gears to has 3:73. 2 Quote Link to comment
Benzfixen Posted February 28, 2019 Author Report Share Posted February 28, 2019 I am in the middle of a Sr swap and have added some extra power parts as well as a 5 link coil over conversion kit so the rear gear is definitely going to need to be taller thank you for your help and Input 2 Quote Link to comment
datzenmike Posted February 28, 2019 Report Share Posted February 28, 2019 The H-190 was used right up till the 2004 2wd 4 cylinder Hardbody and may be being used today, but can't find, and have never heard of, a 3.73 listing only 3.545, 3.70 and 3.889. The 720 ranges from 4.625, 4.375, 4.11, 3.889, 3.70, 3.545 and 3.364 2 1 Quote Link to comment
og620 Posted February 28, 2019 Report Share Posted February 28, 2019 Back in 79 i swapped in the center section from a 77 or newer 810 wagon. You have to trade the side gears because the axel splines are different, Probably easier to find a 720 now . 1 Quote Link to comment
datzenmike Posted February 28, 2019 Report Share Posted February 28, 2019 3.70 on the 810 even the automatics. The later Maxima were 3.545 or worse. 1 Quote Link to comment
Benzfixen Posted March 1, 2019 Author Report Share Posted March 1, 2019 So I'm looking for an H-190 then? 1 Quote Link to comment
paradime Posted March 1, 2019 Report Share Posted March 1, 2019 4 hours ago, datzenmike said: The H-190 was used right up till the 2004 2wd 4 cylinder Hardbody and may be being used today, but can't find, and have never heard of, a 3.73 listing only 3.545, 3.70 and 3.889. The 720 ranges from 4.625, 4.375, 4.11, 3.889, 3.70, 3.545 and 3.364 Yeah, my slip. Meant to type 3:70, but my finger went back to 3 instead of 0. 1 Quote Link to comment
datzenmike Posted March 1, 2019 Report Share Posted March 1, 2019 The 620 truck exclusively uses an H-190 differential but the gears inside can range from 4.885 down to 3.364. Pull the axles out to the side 4" take the driveshaft off and remove 10 bolts and the 3rd member pops right out and back in. You mentioned a 3.83 ratio but the only one close enough is a 3.889 or a 3.70... I don't see that it matters much which. I would definitely leave this for last. Get it going and then see if there is any advantage to this swap. An SR in a heavy truck is like a race horse pulling a cart. 1 Quote Link to comment
datzenmike Posted March 1, 2019 Report Share Posted March 1, 2019 1 minute ago, paradime said: Yeah, my slip. Meant to type 3:70, but my finger went back to 3 instead of 0. Hear ya. I think taht I've proof read it and someone quotes me and I read it and WTF? 2 1 Quote Link to comment
Benzfixen Posted March 2, 2019 Author Report Share Posted March 2, 2019 So I'm looking for an H-190 then? Anyone know where I could get one with the 3.889 ratio 1 Quote Link to comment
wayno Posted March 2, 2019 Report Share Posted March 2, 2019 Shipping is going to be expensive, 5-6 years ago it was $50/60.00 dollars to ship one at the UPS store, it is likely going to be more expensive now. I have what you need, message me and I can go into more detail if your interested. 24 minutes ago, Benzfixen said: So I'm looking for an H-190 then? Anyone know where I could get one with the 3.889 ratio 2 Quote Link to comment
G-Duax Posted March 2, 2019 Report Share Posted March 2, 2019 Shipping anything through a UPS Store is more expensive than just hauling it down to the local UPS hub to ship. The only H190 equipped cars I've seen lately are the QK30 taxi in Japan (made until 2008), that came with a 3.7 final drive. Many of those had the LSD. But to use them in the truck rear end, like the 620, you have to add a spacer in the center the same thickness of the thrust block in the middle of the truck diff (approximately 23mm). I was making them for a while, when I was importing the QK30 LSDs. 2 Quote Link to comment
datzenmike Posted March 2, 2019 Report Share Posted March 2, 2019 Did the Taxi use the same side gear splines as the truck then? 1 Quote Link to comment
G-Duax Posted March 3, 2019 Report Share Posted March 3, 2019 Yes. I have one in my 620. 1 Quote Link to comment
Charlie69 Posted March 3, 2019 Report Share Posted March 3, 2019 1980 720 with the L20B had the 3.889 ratio. Quote Link to comment
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