Click on image for the lowdown. 
====
|
| | Forums66 Topics128,052 Posts1,055,727 Members48,426 | | Most Online14,466
Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
|
| THANKS!
For helping keep this great
old truck web site
on the Internet for over 30 years! and not clogged down
with Ads!  Again, thanks!
|
| | | Joined: Apr 2005 Posts: 1,107 'Bolter | | 'Bolter Joined: Apr 2005 Posts: 1,107 | any advice for smoother up shifts on the vacuum rear in the lower gears? i can split shift fine from 2nd to 4th and from fourth to 2nd. the up shifts in 2nd and third alone are fast and jerky which rock the whole drive train.  when split shifting or just up shifting in 4th are smooth as can be.  i want to be able to do that in the lower gears with all the hills i contend with. | | | | | Joined: Feb 2004 Posts: 29,771 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,771 | Ok, I think I understand, but if not, sorry! You're going from 2nd. low range to 2nd. high, right? Here's how I'd do it: With power applied, move the splitter knob to the "high" position, the quickly ease off the gas and tap the clutch. This allows the planetary unit to shift in a no-load situation, and it's like making any other gear shift. Downshifting is accomplished the same way, but it's usually not necessary to declutch, just pre-select low range, and quickly back off and re-apply power. By making the shift selection with the load on, the diaphragm has time to preload the shift shaft and make a quick change to the other ratio. If I'm not understanding the problem, try to explain it a little more completely.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Jul 2005 Posts: 7 New Guy | | New Guy Joined: Jul 2005 Posts: 7 | Jerry, I think you hit it perfectly. This is as explained in my old Chevrolet owners manual. | | | | | Joined: Apr 2005 Posts: 1,107 'Bolter | | 'Bolter Joined: Apr 2005 Posts: 1,107 | thanks, ill have to try that. when shifting up i was only getting off the gas and back on without tapping the clutch.
sometimes 3rd went smooth and 4th always were smooth that way | | | | | Joined: Dec 2003 Posts: 1,144 'Bolter | | 'Bolter Joined: Dec 2003 Posts: 1,144 | could depend on your rpm as well some transmissions and rears just seem to have a sweet spot. In the 80's I was driving cummins power with roadranger transmissions. Some folks like to wind them out to 2100 rpm every gear I found shifting at 1900 to be smoother. So experiment with your rpm a little also how fast you jump back on the throttle is an issue since the rpms have to drop the higher ratio rear. Now we shift at 1400 rpm oldtimers would be rolling in their graves if they could see it. | | | | | Joined: Apr 2005 Posts: 1,107 'Bolter | | 'Bolter Joined: Apr 2005 Posts: 1,107 | thanks for the advise. smooth shifts with just a touch of the clutch. one guy heard me going through the gears and asked me if a had a 10 speed in that thing and i said nope just an 8. he got this puzzled look on his face :confused: and i just smiled and kept going. | | | | | Joined: Dec 2003 Posts: 1,144 'Bolter | | 'Bolter Joined: Dec 2003 Posts: 1,144 | yes you are correct just tap the clutch enough to release the pressure no need to go all the way to the floor . timing is the key, developing an ear for proper rpm for the shifts. | | | | | Joined: Jun 2005 Posts: 221 Wrench Fetcher | | Wrench Fetcher Joined: Jun 2005 Posts: 221 | you might try installing a vacuum reservoir from a cadillac in the line. | | |
|
|
