drop box and reverser or profab tranny

2005duramax

2005duramax

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Mar 2, 2014
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looking into going odl this winter I am on the fence between a dropbox and reverser or a profab tranny. I am running 513 gears now and am not getting enough speed out of truck (2.6) truck I will be putting a 20 141 in the rear this winter also. I no some guys with the profab that regear the truck using that and a 241 transfer case. I wanna go down to 488s or 456s. I am just wondering what the best bang for the buck is while doing the odl switch kind of a newbie when it comes to this part of it. any help would be awsome
 
Get a Profab reverser and an SCS or Profab drop box. You will never destroy the drop box like you will the OEM transfer case. If you can find them used you will not lose a dime on them when it comes time to re-sell. Check this site's classified section and racingjunk.com often. I would suggest a 6.17 diff ratio, but that's your call.

RK
 
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Not to hijack, But I know Jeremy Denson experienced a failure in a drop box with the 1" gears. Anyone else have issues with the 1" boxes?
 
does it pay to buy a 3 speed tranny or just a one speed? is it going to be a pain in the ass to drive in pits and why such a high gear? does the one speed tranny make up for the tall gears?
 
6.17 gears are a very low gear. The higher the #, the lower the gear or "speed" is. Most truck pullers use the Profab single speed reverser, it is 1 to 1 ratio, meaning your final drive gearing is determined by gearing your drop box to the desired final drive.

Example:

1.143 (1600 gear set) x 2 (lower drop box fixed ratio) x 6.17 (axle ratio) = 14.1 (final drive)

Profab chart:

http://nebula.wsimg.com/8c1465431b87bcf219b987de0fd7d19e?AccessKeyId=DBFF22BE86A5B0CAC35A&disposition=0&alloworigin=1

http://www.profabmachineinc.com/products.html
 
I believe even with the 3 speeds they are a very small split so it won't impact much in the pits. One reason you see most people winching their trucks on the trailers.
 
Has anyone used the profab dropbox and reverser combo unit? Looks like that may be a good choice for someone who is now going to ODL.
 
bigstacks95 said:
Not to hijack, But I know Jeremy Denson experienced a failure in a drop box with the 1" gears. Anyone else have issues with the 1" boxes?
Click to expand...

Yea that wasn't a fun ride


zstroken said:
I believe even with the 3 speeds they are a very small split so it won't impact much in the pits. One reason you see most people winching their trucks on the trailers.
Click to expand...

Basically it would be the same as 1st 4.10, 2nd 4.88 and 3rd 5.13 gear ratio
 

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We ran the probably reverser/Dropbox single unit. Zero issues. Made adjusting the clutch easier as there was not a reverser attached to the bellhousing. Just slide the shaft and couplers back and drop the bellhousing.
 
crower style clutch
browell bellhousing
profab reverser 1.5'' input
profab transfer case 1+3/8 wide gears
SQHD rear 6.20
Dana 60 front 6.17 gears

thats the set up i've ran for a few years, another tip i would add is make sure your slip shaft in the rear driveshaft is around 2''. i broke enough of the 1480 and 1550 slips to fill a 5 gallon bucket. **edit- if you run gears like 4.56, 4.88s etc. that will put more torque on your driveshafts and more stress on the driveline. generally you want them running as fast as you can.
 
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Ok so I see that profab has a reverser and drop box with the 13/8 gears for 4500 that seem about right for what I am going to need I didn't get a chance to call anyone yet kinda wanna learn more before I call them. And will my valiar triple disk work with these bell housings? I don't hear many people talking about using Valiras on old setups.
This is the one I was talking about on there site third one down.also is there any preference between the 20141 rears and the sqhd? Pros and cons I can get a 20141 threw work housing for 200 bucks
http://www.profabmachineinc.com/products.html
 
2005duramax said:
Ok so I see that profab has a reverser and drop box with the 13/8 gears for 4500 that seem about right for what I am going to need I didn't get a chance to call anyone yet kinda wanna learn more before I call them. And will my valiar triple disk work with these bell housings? I don't hear many people talking about using Valiras on old setups.
This is the one I was talking about on there site third one down.also is there any preference between the 20141 rears and the sqhd? Pros and cons I can get a 20141 threw work housing for 200 bucks
http://www.profabmachineinc.com/products.html
Click to expand...

i run the divorced reverser/dropbox set up, i think what you're talking about is the one thats one assembly. never ran one but heard they're nice. and there are 20-145's and SQHDs. 20-145 is a newer rear end and has an aluminum center. SQHD is older steel center, idk specifics but both seem to work fine. you'll just pay lots more for a ring and pinion for a 20-145. dont go off in left field with a rear end you wont be able to get parts for like spools, etc... try and run similar stuff to what other people you pull with run so when you break sh!t on friday night and need to pull saturday night the odds of the parts you need laying around are pretty high. at least its worked that way for me in the past.

edit... forgot to answer your clutch question but i would say no. my bellhousing is meant to fit around a 4 disk 11'' crower clutch. my guess is you're running an 1+3/8 input shaft now and if i was going to order a new reverser i'd get it with 1.5'' input to be safe. mine as well sell you're valair clutch and buy a crower style. its worth every penny when it comes to driving the truck out of the hole imo. especially on a dmax
 
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duramaxsandwich said:
i run the divorced reverser/dropbox set up, i think what you're talking about is the one thats one assembly. never ran one but heard they're nice. and there are 20-145's and SQHDs. 20-145 is a newer rear end and has an aluminum center. SQHD is older steel center, idk specifics but both seem to work fine. you'll just pay lots more for a ring and pinion for a 20-145. dont go off in left field with a rear end you wont be able to get parts for like spools, etc... try and run similar stuff to what other people you pull with run so when you break sh!t on friday night and need to pull saturday night the odds of the parts you need laying around are pretty high. at least its worked that way for me in the past.

edit... forgot to answer your clutch question but i would say no. my bellhousing is meant to fit around a 4 disk 11'' crower clutch. my guess is you're running an 1+3/8 input shaft now and if i was going to order a new reverser i'd get it with 1.5'' input to be safe. mine as well sell you're valair clutch and buy a crower style. its worth every penny when it comes to driving the truck out of the hole imo. especially on a dmax
Click to expand...

20-145s aren't all aluminum most are cast steel. Both SQHD and 20-145 centers are available in cast aluminum but I wouldn't run them in a diesel.
Billet aluminum is a different story but very pricey $.

A6752F66-5467-45AB-85DF-8676737CD34D_zpszlflb22u.jpg
 
JL Builders said:
20-145s aren't all aluminum most are cast steel. Both SQHD and 20-145 centers are available in cast aluminum but I wouldn't run them in a diesel.
Billet aluminum is a different story but very pricey $.

A6752F66-5467-45AB-85DF-8676737CD34D_zpszlflb22u.jpg
Click to expand...

I hadn't heard of anyone around here breaking an aluminum 20-145.
 
JL Builders said:
20-145s aren't all aluminum most are cast steel. Both SQHD and 20-145 centers are available in cast aluminum but I wouldn't run them in a diesel.
Billet aluminum is a different story but very pricey $.

A6752F66-5467-45AB-85DF-8676737CD34D_zpszlflb22u.jpg
Click to expand...

Was this breakage in a stock 20-145 housing or a fabricated housing?

I am not very familiar with the drop boxes, but do the SCS drop boxes also have different thicknesses of gears or is it only the profab that had the option of 1" gears? It just seems that when talking about gear thickness the profab name is used not the scs.
 
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I think some of Profab's early built boxes used the 1" wide gears that would sometimes fail in high HP pullers. SCS boxes have always used the same width gear to my knowledge.
 
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