Posted By: bfury
727 Low Reverse Servo Question - 11/22/12 01:54 AM
Are all the rear (low/reverse) servos in the '71 up 727's the same size? We have a cracked one and looked at some from other 727's that look different.
727 Low Reverse Servo Question
Posted By: 572stealth
Re: 727 Low Reverse Servo Question - 11/22/12 02:21 PM
If you are using a low band apply valve body just get a billet aftermarket one, seen many cracked stock ones.
Posted By: 440Jim
Re: 727 Low Reverse Servo Question - 11/22/12 03:05 PM
It is my understanding that the 1967-1978 are the same. The ones newer than 1978, I am not sure about.
I agree the billet (rather than cast) aftermarket ones are a good upgrade. Many also come with a HD (extra thick) retainer; the stock one can be bent and allow the servo to pop out. Sold by CRT, and mrRandyJ in the Moparts.com parts for sale section. Less than $100 with a one-piece billet servo (no spring), HD retainer, HD spring.
https://board.moparts.org/ubbthreads/show...rue#Post7443374
If using a stock one, shim the servo as close to solid as you can (no spring travel).
I agree the billet (rather than cast) aftermarket ones are a good upgrade. Many also come with a HD (extra thick) retainer; the stock one can be bent and allow the servo to pop out. Sold by CRT, and mrRandyJ in the Moparts.com parts for sale section. Less than $100 with a one-piece billet servo (no spring), HD retainer, HD spring.
https://board.moparts.org/ubbthreads/show...rue#Post7443374
If using a stock one, shim the servo as close to solid as you can (no spring travel).
Posted By: bfury
Re: 727 Low Reverse Servo Question - 11/23/12 04:33 PM
Thanks for the help. This trans is in a 4 wd plow pickup. Don't know if that makes a difference.
Posted By: JohnRR
Re: 727 Low Reverse Servo Question - 11/23/12 04:37 PM
Quote:
Thanks for the help. This trans is in a 4 wd plow pickup. Don't know if that makes a difference.
no it doesn't .
Posted By: 440Jim
Re: 727 Low Reverse Servo Question - 11/23/12 05:26 PM
Quote:From what I know, many pickup plow drivers shift from Drive to Reverse and back often. If not careful, this is hard on the rear servo. And shimming the servo solid takes away the cushioning effect, which might be a double edged sword. i.e. it doesn't slam the piston plug against the piston, but the solid servo might shock the strut, etc. I am not sure.
Thanks for the help. This trans is in a 4 wd plow pickup. Don't know if that makes a difference.
So for that application, although a billet servo is not likely to crack like a cast factory part;
I wonder if a Sonnex billet servo that retains the cushion spring assembly might be a better way to go?
These are only about $15. Transmission Technologies
They list one for the older 727s (22912), one for 1994-1996 (22912B) and another for 1997 and newer (22912C)
http://www.sonnax.com/system/instructions/22912-IN.pdf
And Superior makes this "super servo" with features to resist cocking in the bore.
transmissiontechnologies.com Transmission Technologies
Posted By: John_Kunkel
Re: 727 Low Reverse Servo Question - 11/23/12 06:58 PM
The only time a rigidized rear servo piston is an advantage is on a manual 1-2 upshift; if you don't do manual upshifts often, you're better off leaving the unmodified rear servo because it's easier on parts....especially in a vehicle that changes direction often.
Posted By: bfury
Re: 727 Low Reverse Servo Question - 11/27/12 03:11 AM
Thanks all for your help. Good info taken to heart.