Good Sam Club Open Roads Forum: Class C Motorhomes: Rear gear ratio
Open Roads Forum Already a member? Login here.   If not, Register Today!  |  Help

Newest  |  Active  |  Popular  |  RVing FAQ Forum Rules  |  Forum Posting Help and Support  |  Contact  

Search:   Advanced Search

Search only in Class C Motorhomes

Open Roads Forum  >  Class C Motorhomes  >  Class C

 > Rear gear ratio

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Page of 3  
Next
76 Rambler

Kansas City, Mo.

New Member

Joined: 11/01/2020

View Profile



Posted: 11/01/20 05:44pm Link  |  Quote  |  Print  |  Notify Moderator

I bought a 24 ft class c 1976 Holiday Rambler (E-350 chassis) last year, and recently had the motor rebuilt (ford 460). I ditched the motorcraft 4350 carb, and went with a holley 650 dp. I had them install a bigger cam on rebuild. It absolutely has plenty of power taking off from a stop, or climbing hills with no downshift. The transmission is a c6. The good thing is that it's a c6. The bad thing is that it's a c6, and has no overdrive, which means I'm running 2700 rpm at 55 mph and 3150 at 65. It was built when the federal speed limit was 55, and geared for that. I'd like to put a taller rear end in it to reduce my rpm's at 65. I'm just looking to see if anybody else has been through this scenario, and how far is too far on swapping the ratio. I know I'm going to lose power on the low end, and at the lower end of a shift. I'm sure I can make up for any bogging down after shifting gears with a stiffer shift modulator spring to shift at a higher rpm. I haven't lifted it yet to determine what's in it now.

* This post was edited 11/01/20 06:32pm by 76 Rambler *

Lwiddis

near Bishop, California

Senior Member

Joined: 08/12/2016

View Profile



Good Sam RV Club Member

Offline
Posted: 11/01/20 05:49pm Link  |  Quote  |  Print  |  Notify Moderator

2700 rpm at 55 mph? Yes, time for a change. What rear end do you have now?


Winnebago 2101DS TT & 2020 Chevy Silverado 1500 LTZ Z71, 300 watt solar-parallel & MPPT, Trojan T-125s. TALL flag pole. Prefer USFS, COE, BLM, NPS, TVA, state & county camps. Bicyclist! 14 year Army vet-11B40 then 11A - (MOS 1542 & 1560) IOBC & IOAC grad


T18skyguy

Eugene, OR

Senior Member

Joined: 12/13/2004

View Profile



Good Sam RV Club Member


Posted: 11/01/20 07:34pm Link  |  Quote  |  Print  |  Notify Moderator

You might look into a Gear Vendors Overdrive. It works great with the C6 and you'll have 6 speeds. It's a nice setup and they been around forever.


Retired Anesthetist. LTP. Pilot with mechanic/inspection ratings. Between rigs right now.. Wife and daughter. Four cats which we must obey.

Grit dog

Black Diamond, WA

Senior Member

Joined: 05/06/2013

View Profile


Offline
Posted: 11/01/20 07:37pm Link  |  Quote  |  Print  |  Notify Moderator

^ But re-gearing it will be waaay cheaper, albeit not as useful as a GV.
It likely has 4.10s, maybe 4.56 but doubt it. Short tires are contributing to the rpms as well.
Healthy big block will pull a lot but I wouldn’t go any taller than 3.73s, unless you’re just driving around the prairies. Then you could probably gear it up a bit more.


"Yes Sir, Oct 10 1888, Those poor school children froze to death in their tracks. They did not even find them until Spring. Especially hard hit were the ones who had to trek uphill to school both ways, with no shoes." -Bert A.

whemme

Spencer, IA

Senior Member

Joined: 08/26/2004

View Profile



Posted: 11/01/20 08:05pm Link  |  Quote  |  Print  |  Notify Moderator

How was it possible to install a bigger cam. I can’t see how a bigger cam would fit into the existing bearing journals that hold the cam.


2002 Born Free 26' RSB Motorcoach
2005 Chevrolet Malibu LS Toad

time2roll

Southern California

Senior Member

Joined: 03/21/2005

View Profile



Good Sam RV Club Member


Posted: 11/01/20 08:37pm Link  |  Quote  |  Print  |  Notify Moderator

whemme wrote:

How was it possible to install a bigger cam. I can’t see how a bigger cam would fit into the existing bearing journals that hold the cam.
The lobes that activate the valves/lifters are taller and longer duration of lift.

For the Op... you probably just want to move about 10% so 4.56 to 4.10 would be an example or 4.10 to 3.73 depending of course on what is available. Your RPM will move down the exact same percentage. Speedometer will need corrected, I think a replacement gear on the speedo cable.


2001 F150 SuperCrew
2006 Keystone Springdale 249FWBHLS
675w Solar pictures back up

whemme

Spencer, IA

Senior Member

Joined: 08/26/2004

View Profile



Posted: 11/01/20 08:59pm Link  |  Quote  |  Print  |  Notify Moderator

time2roll wrote:

whemme wrote:

How was it possible to install a bigger cam. I can’t see how a bigger cam would fit into the existing bearing journals that hold the cam.
The lobes that activate the valves/lifters are taller and longer duration of lift.

That is a cam with modified cam lobe profiles - not a bigger cam!

time2roll

Southern California

Senior Member

Joined: 03/21/2005

View Profile



Good Sam RV Club Member


Posted: 11/01/20 09:31pm Link  |  Quote  |  Print  |  Notify Moderator

Read some Hot Rod magazines. Cam with a larger lift is considered a bigger cam. Cam with a longer duration that shifts the torque curve up in rpm is also considered a bigger cam. Bearing journals are always the same.

Same with a bigger crankshaft usually refers to a longer stroke for bigger displacement. Sometimes the journal has an offset grind to increase stroke. Same effect but smaller journal but it is considered 'bigger'. Main journals are always the same unless damage repair is needed.

30sweeds

Iowa

New Member

Joined: 03/24/2018

View Profile


Offline
Posted: 11/02/20 07:23am Link  |  Quote  |  Print  |  Notify Moderator

Our old Winnie had 3:73's in it.I originally thought they were a little tall but had no problem pulling a 19 ft boat.About 2550 at 65 mph.Not great but livable.First MH had 4:10's and 60 mph was about it.Plenty of power but uncomfortable down the road.No offense but any trans swap such as an E4OD or a Gearvenders unit would cost more than the old Holiday is worth. 460's are the real deal,though. More power than my current V10.

theoldwizard1

SE MI

Senior Member

Joined: 09/07/2010

View Profile


Offline
Posted: 11/02/20 07:28am Link  |  Quote  |  Print  |  Notify Moderator

T18skyguy wrote:

You might look into a Gear Vendors Overdrive. It works great with the C6 and you'll have 6 speeds. It's a nice setup and they been around forever.

Yes, but they are expensive.

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Page of 3  
Next

Open Roads Forum  >  Class C Motorhomes  >  Class C

 > Rear gear ratio
Search:   Advanced Search

Search only in Class C Motorhomes


New posts No new posts
Closed, new posts Closed, no new posts
Moved, new posts Moved, no new posts

Adjust text size:




© 2021 CWI, Inc. © 2021 Good Sam Enterprises, LLC. All Rights Reserved.