Rack & Pinion Questions - Diesel Forum

Csgod0 · 11-18-2009, 10:35 AM

Hello, I'm a brand new IDI owner, but I've been reading here for days and have done most of my homework.
I bought a 1988 F-350 dually with the C6, and find that I'm limited at 55mph comfortably without running high RPM.

I plan on pulling a car trailer come spring here in Ohio, but currently I'm running empty with a cap on top.

I've read into GV units, or US Gear dual aux under/over, but with my new purchase I'm kinda strapped for cash, but want to be able to ride at 65 without staring at my tach. I am unsure of what gears are in the rear end, but I know based on the year and trans I imagine the axle is the sterling 10.25".

4wdfactory sells a 3.55 ring&pinion set for the rear for $195+tax. It feels like I have the 4.10, but I'd have to check.

Would it be worthwhile to go ahead and regear the rear end ?

osufireman · 11-18-2009, 11:11 AM

Re-gearing your truck does seem like the cheapest option, next to installing a E4OD with all its TCM and wiring harness.

There should be an axle code in the door tag on the driver side, if you still have the owners manual you can look it up, or post it up here and I'm sure someone can help you figure it out. Or, look at the ID tag on the rear pumpkin.

Is the truck 4x4? If so you will need to chance both front and rear gear sets. Just keep in mind that changing gear sets from, say, 4.10 to 3.55 will change your towing capacity, sometimes dropping it a little bit.

Csgod0 · 11-18-2009, 11:23 AM

sadly, its 2wd, so i have some flexibility with not having to modify a 4wd system. I dont plan on pulling more than 10k lbs anytime in the future, so loosing some capacity for sake of some highway driveability doesn't bother me too much. I'll post the axle code tonight after i look it over. BTW, alittle off topic, any recommendation for a sealer for my undercarriage? not a spec of rust on the frame and I want to keep it that way.

NH2112 · 11-18-2009, 10:07 PM

It'll be loud in the cab but you can run that engine right up against the governor all day long without any problems.

M.L.S.C. · 11-19-2009, 03:43 AM

Running at high engine speeds makes for a VERY lousy fuel economy tho, which is what he's trying to avoid. Csgod0, there are also 3.08 gear sets for the Sterling axle, I know of one person who has that and he's quote happy with it, he don't tow much at all tho. That said, with the 3.08 gears in 3rd you'll be turning at about 1950 rpms at 60mph, which is the same as how my truck does with the 4.10 gears and the E4OD trans in 4th gear. So assuming you now have 4.10s too, with the 3.08 gears you're looking an engine speed decrease of 600 rpms at 60 mph, which means if you do still wanna run at your current engine speed (about 2600 rpms at 60mph) with the 3.08s you will now be flying low at 80 mph

As far as towing goes, with the 3.08s your 1st gear will feel much like starting in 2nd gear now, it will get the job done but you gotta give yourself plenty of time to accelerate. Your 3rd gear will be the same as an E4OD truck with 4.10s and they to in OD just fine, so no worries there till you come up to a long hill, then you gotta downshift (but then again, so do I). Overall I think the 3.55s aren't worth the money to purchase and install, either go with 3.08s and trade off acceleration and pulling power for fuel economy and top speed, or just live with the 4.10s and drive slower. By the way, for what it's worth, on the interstate I only drive 57 mph, I set the cruise so the engine runs at 1900 rpms and enjoy my 20 mpg fuel economy

StrokerSmoker7.3 · 11-19-2009, 08:01 PM

As was said before, it will be loud on the cab and fuel milage won't be great but you can run 70 MPH at 3200 rpm all day long. I have the same setup as you, 4.10s and a C6 and don't think twice about running 70 on the interstate. What is the governed RPMs on these?

NH2112 · 11-19-2009, 08:32 PM

The wind resistance from traveling 65mph instead of 55 will account for a lot more of the reduction in mileage you'll see than the higher engine rpm.

Csgod0 · 11-20-2009, 12:27 AM

yeah, I have the 4.10s. Honestly I dont see myself pulling anything until winter is over, and even then if it comes right down to it that some higher gears dont cut it, I'll suck it up and put the 4.10 back in. 3.08 does sound nice. I'm usually cruising the highway at 55MPH doing 2600RPM. the IDIs are a torque monsters anyway, so its not like it will struggle to go or pull even if I do change the gearset. My birthday present to myself will be a GV kit for sure.

I found this doing a quick google search, would something like this be worthwhile? I'm all armchair theory at the moment. Motive Gear Set - RWK Haus Supply

Csgod0 · 11-23-2009, 01:57 PM

I made up my mind, and I'm going to try to convert from 4.10 to 3.55 until track season comes. A local seller has a 3.55 ring&pin set for $40 out of an 88 f350. What else would comprise this swap? Would I have to buy an install kit or would it be cheaper to have a repair place do it?

osufireman · 11-23-2009, 07:07 PM

Quick question for you, are you installing the different gear sets yourself? Is it difficult? I only ask because I've thought about changing out my 4.10 in the future, and doing it myself, but some people recommended not tackling this one, should leave it to the shop.

StrokerSmoker7.3 · 11-23-2009, 07:25 PM

I've never done a swap but I've heard it can be tricky. However, I have also heard that the Sterling 10.25s are some of the easiest to RR gears on. if it were me and I had someone with good experience there to help, I'd go for it but otherwise I'd leave it to a shop because you can mess it up and when you do it prolly ain't gonna be good.

LMJD · 11-24-2009, 08:54 AM

It's not like changing a set of belts. Pinion bearings are always replaced during a gear change, and usually carrier brgs. Pinion brg preload has to be set. Carrier bearing preload has to be set. Gear contact pattern has to be set correctly using bearing blue, both coast and drive side. As it's set, the brg preloads and backlash are affected and then they have to be redone and checked. If it's a used gear set, the drive side pattern is a hair closer to the tooth toe than a new set, and on and on. If a rear end is done incorrectly longevity and a gear whine results. If done REAL incorrectly even shorter longevity and a louder whine.

Quote:

I have also heard that the Sterling 10.25s are some of the easiest to RR gears on.

You heard wrong, they're a major pain compared to overhauling a third member drop in unit like most all other rear ends.

Csgod0 · 11-24-2009, 03:51 PM

I picked up my 3.55 R&P set from a cool guy in Alexandria,KY. $40 got me a set that wasn't new, but it was still so unused it still had the tooling marks on it.

I am going to call around about having someone put it in, because I dont have the knowledge, nor the tools to complete the job. I figure I was getting around 11mpg empty with the 4.10 at 55mph constantly, so this should make a good difference.

Milford,OH is nothing but bars and automotive stores I swear. So, I know some people all over, and I'm going to see if a friend of a friend will put this in for cheap.

StrokerSmoker7.3 · 11-24-2009, 08:19 PM

Quote:

Originally Posted by LMJD

You heard wrong, they're a major pain compared to overhauling a third member drop in unit like most all other rear ends.

OK, thanks for puttin that out there. I've never personally done one so I didn't know. What makes them more of a pain than a 3rd member? Is it because they can't just be removed and set on a bench?

M.L.S.C. · 11-25-2009, 06:38 AM

Well that's a pretty darn good reason if you ask me, lol