NorCal720xx Posted February 11, 2020 Report Share Posted February 11, 2020 Hello all, I traded for an 83 720 a couple years ago. It's complete for the most part except that the original 5sp (assumed OE was 5sp) was replaced by a 4sp. I'm slowly working through the truck to freshen it up in several areas; suspension, some electrical, redline carb?, Etc. It seems that much of what I will need is available at some capacity online. The one exception I have found is the backup light and housing. This model has the backup lamp separate from the taillight assembly tucked into the valance. Any known sources to find a replacement?? Regarding the 4sp: I initially thought I needed (wanted) to swap out the 4sp for a 5sp. It's pretty high geared but that is with 31/10.5/15 tires. I'm guessing that a tire size closer to stock (215/75/15) will bring the gear ratios down. Currently considering 235/75/15. This rig is going to be a run-around town weekender and dirt road cruiser at best and not a fwy commuter by any means. Should I be seeking out a replacement 5sp or will the 4sp suit my needs?? Any and all criticism, advise, knowledge, perspective is appreciated. 1 Quote Link to comment
datzenmike Posted February 11, 2020 Report Share Posted February 11, 2020 If your build date is January '83 or newer your truck only came with a 5 speed. If you drive primarily in town a 4 speed is fine but if you commute out on the highway or live out of town a 5 speed is nice. 2 Quote Link to comment
Madkaw Posted February 11, 2020 Report Share Posted February 11, 2020 The back up lights pop up on some FB pages for sale, folks doing part outs . Smaller tires might make all all the difference . I don’t have enough 720 driving miles to be a true judge, but sounds like we have the same usage in mind. You could probably keep the 4 speed and be fine. Good 5 speeds are hard to come by and that year they weren’t that strong. Get a newer 71C trans and adjust to fit. 2 Quote Link to comment
datzenmike Posted February 11, 2020 Report Share Posted February 11, 2020 Stock '84 720 4x4 are just under 28" (27.75") tall. Width you can select what ever you wish as long as you keep the height correct. The 4x4s had 4.11 gearing in the differentials. A 31" tire is the same as if you took the 4.11s out and put 3.68s in.... a terrible choice. A 270/60R15 is the same width as the 31" but is 27.7" tall. 2 Quote Link to comment
captain720 Posted February 11, 2020 Report Share Posted February 11, 2020 235/75/15 is the perfect tire for a 4wd with 4.11s for off road and in town use. You can get a 720 places full sizes guys can't even dream of with open diffs and a good set of 235/75/15, tread and the right line is more important than size hands down. I have a couple sets of 235/75/15 and have loved all of them. 2 Quote Link to comment
Madkaw Posted February 11, 2020 Report Share Posted February 11, 2020 8 hours ago, datzenmike said: Stock '84 720 4x4 are just under 28" (27.75") tall. Width you can select what ever you wish as long as you keep the height correct. The 4x4s had 4.11 gearing in the differentials. A 31" tire is the same as if you took the 4.11s out and put 3.68s in.... a terrible choice. A 270/60R15 is the same width as the 31" but is 27.7" tall. My 5/83 has 3.88 gears so his might even be higher than 4.11 1 Quote Link to comment
datzenmike Posted February 11, 2020 Report Share Posted February 11, 2020 Geez I forgot about the 3.889 gears. That's way worse. 1 Quote Link to comment
Madkaw Posted February 11, 2020 Report Share Posted February 11, 2020 10 minutes ago, datzenmike said: Geez I forgot about the 3.889 gears. That's way worse. I don’t find them that bad actually , but don’t have experience driving other gears sets on these trucks . With stock wheel size she has come good acceleration for those gears . The biggest issue I see is highway cruising as the OP stated . The overdrive might not keep you in ideal rpm range and it will feel weak on the hills . 2 Quote Link to comment
datzenmike Posted February 11, 2020 Report Share Posted February 11, 2020 It would be terrible off road and climbing. Sluggish in town for pick up and may not be usable into the wind on windy days. My 620 had a 720 transfer case, 4.11s and 12.5 x33". On the highway had to down shift for hills to keep up with traffic. Windy days stayed in 4th and I don't remember ever passing anyone.... and this was with a Z24 engine swap. 1 Quote Link to comment
Madkaw Posted February 11, 2020 Report Share Posted February 11, 2020 I cannot comment on off reading , but I thought low 4 was handle most things ? My truck is not sluggish around town, it’s quite peppy. I would imagine with 33’s it would be much worse , but I’m running 235/75’s . 1 Quote Link to comment
NorCal720xx Posted February 11, 2020 Author Report Share Posted February 11, 2020 10 minutes ago, datzenmike said: It would be terrible off road and climbing. Sluggish in town for pick up and may not be usable into the wind on windy days. My 620 had a 720 transfer case, 4.11s and 12.5 x33". On the highway had to down shift for hills to keep up with traffic. Windy days stayed in 4th and I don't remember ever passing anyone.... and this was with a Z24 engine swap. I'll crawl around and look at the boxes for a tag showing gear ratios. Guess I'd find it on the axle housing like US rigs? I tried the VIN but no luck yet. JN6ND06Y1DW005XXX 1 Quote Link to comment
Madkaw Posted February 11, 2020 Report Share Posted February 11, 2020 1 minute ago, NorCal720xx said: I'll crawl around and look at the boxes for a tag showing gear ratios. Guess I'd find it on the axle housing like US rigs? I tried the VIN but no luck yet. JN6ND06Y1DW005XXX The tag is on the passenger side inner fender wall inside the engine compartment -you will see all the numbers there 2 Quote Link to comment
NorCal720xx Posted February 11, 2020 Author Report Share Posted February 11, 2020 34 minutes ago, Madkaw said: The tag is on the passenger side inner fender wall inside the engine compartment -you will see all the numbers there Axle: HF38 Also... After the engine code is an (S). What does that signify? 1 Quote Link to comment
datzenmike Posted February 11, 2020 Report Share Posted February 11, 2020 Z24S= carburetor Z24i= throttle body injection (used from April '85 on) 1 Quote Link to comment
NorCal720xx Posted February 11, 2020 Author Report Share Posted February 11, 2020 1 hour ago, Madkaw said: The tag is on the side inner fender wall inside the engine compartment -you will see all the numbers there 16 minutes ago, datzenmike said: Z24S= carburetor Z24i= throttle body injection (used from April '85 on Axle code looks to be HF 38. 1 Quote Link to comment
datzenmike Posted February 11, 2020 Report Share Posted February 11, 2020 H= bolt in 3rd member F = 190cm diameter ring gear 1 1 Quote Link to comment
Madkaw Posted February 11, 2020 Report Share Posted February 11, 2020 3 minutes ago, NorCal720xx said: Axle code looks to be HF 38. 3.889:1 axle ratio- same gears as mine 1 1 Quote Link to comment
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