5.3/T56 Diff Gear Selection
06-30-2013, 04:32 AM
#1
5.3/T56 Diff Gear Selection
Short Version:
4.88's, 5.38's, or ?? in 5.3/T56 in 95 ECSS. Will run 28 or 29 inch tires. Engine will have 243's milled .030" and Comp 215/223 .604/.61 112+5. 80% highway, occasional light towing.
Long Version:
I am in the process of collecting parts to rebuild a 6Lug 14 Bolt SF I picked up a couple weeks ago for my 95 ECSS 2WD and would like some opinions on gears. Engine will have 243's milled .030" and Comp 215/223 .604/.61 112+5. And I will run 28 or 29 inch tires. I have been in touch with axisT6 (Bryan) through PM and he has been really helpful with getting me quotes and giving me his opinion/insight on this. I don't want to pester him with too many questions so I figured I would ask others on here as well. Especially anyone with a T56 in a truck
From looking at other T56 swaps in trucks, most are running 4.56's or 4.88's at most. My 95 originally had a NV3500 with 3.42 gears an overall ratio of 13.7484 in first and 2.4966 in fifth. With that setup, I had a good amount of get up and go in first due to the low gearing. At times though, I felt it was too low (GM suggested first only for towing, with payload, etc.). As for use: I do 80% highway driving (60 or 70 with cruise set). I only tow or haul anything very occasionally and it's light, couple jet ski's or a jet boat.
In order to keep the same torque multiplication in first I would need 5.13's (13.6458 overall) and that gives me 2.565 in sixth. The RPM difference between 4.88 and 5.38 at 70 MPH is 200 RPM (2000 vs 2200 respectively) with 29" tires.
To better compare trans and overall drive ratios of a few transmissions I made a couple tables. First, transmission ratios:
Now, the overall ratios:
When I look at this from RPM and shift point perspective the 5.38's that Bryan recommended seem very logical. But then I see no other t56's with gears that are that low and I am not sure how much the 5.3 will like to rev on the highway. I keep going back and forth.
Any thoughts? Am I just overthinking this and should stick with the 5.38's Bryan advised? Should I stop comparing this to auto transmissions since they have a TC and I will not. For those with this trans, what is it like with the gears you are running?
4.88's, 5.38's, or ?? in 5.3/T56 in 95 ECSS. Will run 28 or 29 inch tires. Engine will have 243's milled .030" and Comp 215/223 .604/.61 112+5. 80% highway, occasional light towing.
Long Version:
I am in the process of collecting parts to rebuild a 6Lug 14 Bolt SF I picked up a couple weeks ago for my 95 ECSS 2WD and would like some opinions on gears. Engine will have 243's milled .030" and Comp 215/223 .604/.61 112+5. And I will run 28 or 29 inch tires. I have been in touch with axisT6 (Bryan) through PM and he has been really helpful with getting me quotes and giving me his opinion/insight on this. I don't want to pester him with too many questions so I figured I would ask others on here as well. Especially anyone with a T56 in a truck
From looking at other T56 swaps in trucks, most are running 4.56's or 4.88's at most. My 95 originally had a NV3500 with 3.42 gears an overall ratio of 13.7484 in first and 2.4966 in fifth. With that setup, I had a good amount of get up and go in first due to the low gearing. At times though, I felt it was too low (GM suggested first only for towing, with payload, etc.). As for use: I do 80% highway driving (60 or 70 with cruise set). I only tow or haul anything very occasionally and it's light, couple jet ski's or a jet boat.
In order to keep the same torque multiplication in first I would need 5.13's (13.6458 overall) and that gives me 2.565 in sixth. The RPM difference between 4.88 and 5.38 at 70 MPH is 200 RPM (2000 vs 2200 respectively) with 29" tires.
To better compare trans and overall drive ratios of a few transmissions I made a couple tables. First, transmission ratios:
Now, the overall ratios:
When I look at this from RPM and shift point perspective the 5.38's that Bryan recommended seem very logical. But then I see no other t56's with gears that are that low and I am not sure how much the 5.3 will like to rev on the highway. I keep going back and forth.
Any thoughts? Am I just overthinking this and should stick with the 5.38's Bryan advised? Should I stop comparing this to auto transmissions since they have a TC and I will not. For those with this trans, what is it like with the gears you are running?
06-30-2013, 01:24 PM
#2
I'm running 4.56's with 31" tall tires and spin around 1660 RPM in 6th at 65mph. I think the low RPM's help with fuel economy. 1st is plenty useful and I could never spin the tires in first even with mild heads/cam, but my tires are sticky. Now with the turbo 1st and 2nd are useless at WOT. It's my DD, never sees the track though.
If it were me, I would use 4.56's with your tires, or maybe even 4.33's. But it's all personal preference. Anything will work.
If it were me, I would use 4.56's with your tires, or maybe even 4.33's. But it's all personal preference. Anything will work.
06-30-2013, 10:37 PM
#3
I'm running 4.56's with 31" tall tires and spin around 1660 RPM in 6th at 65mph. I think the low RPM's help with fuel economy. 1st is plenty useful and I could never spin the tires in first even with mild heads/cam, but my tires are sticky. Now with the turbo 1st and 2nd are useless at WOT. It's my DD, never sees the track though.
If it were me, I would use 4.56's with your tires, or maybe even 4.33's. But it's all personal preference. Anything will work.
If it were me, I would use 4.56's with your tires, or maybe even 4.33's. But it's all personal preference. Anything will work.
What rpm did you shift at before the turbo during normal daily driving? Thanks for the reply!
I also found this:
https://www.performancetrucks.net/fo...7/#post3705709
I swaped out my 4.30's for 5.13's yesturday and I'm very happy. It seems to be about perfect for my tire height (275/55-20's). 1950rpm @ 70 mph and 2200 @ 80 mph in 6th. I was torn between 4.88's and 5.13's. The final drive is equivalent to a f-body with stock tire height and 4.10's for comparison. The 5.13's sound steep but not when you are comparing a 25.5" tall f-body tire to my 31.75". Just thought i'd share.
06-30-2013, 11:22 PM
#4
They are Hankooks Ventus RH06. I meant I couldn't do a rolling burnout. If I dumped the clutch I definitely can break them loose, but that is VERY hard on a T56 that's trying to haul around a heavyass truck. I could chirp 2nd and 3rd easily on shifts. I shift at 6200 because it's my DD and I want/need it to hold together. The clutch is a spec 3+ and it's more than capable.
06-30-2013, 11:36 PM
#5
They are Hankooks Ventus RH06. I meant I couldn't do a rolling burnout. If I dumped the clutch I definitely can break them loose, but that is VERY hard on a T56 that's trying to haul around a heavyass truck. I could chirp 2nd and 3rd easily on shifts. I shift at 6200 because it's my DD and I want/need it to hold together. The clutch is a spec 3+ and it's more than capable.
Thanks for the info, 6200 seems to be a common shift point. I'll have to figure mine out when I get it all put together.
At this point I am leaning towards 5.13's.
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