Wednesday, 26 August 2020
Wednesday, 15 July 2020
The Saga Of My Doug Nash 4+1 5 Speed Transmission.
My 1986 Monte Carlo SS had an original Doug Nash 4+1 5 speed transmission in it when I bought it in 2001.
At that time this car had a bit of a reputation for being hard on transmission parts and clutches.
That problem turned out to be caused by the Lakewood bellhousing never having been aligned properly.
Once that was done the life of parts and clutches increased significantly.The LuK clutch that is in it now has been in use for over fifteen years.
The shifter that was in it was a Hurst Competition Plus and it was worn out.I replaced it with a Hurst Vertical Gate II Inline Shifter,or a Ram Rod as they are also known.
It needed a bit of "tweaking" to get it the way I wanted it.Custom made bushings and shims took all the play out of it,and a custom made reverse lockout was the icing on the cake !! The reverse lockout was the brainchild of Steve Best and Frank McGilivary.
You can see the reverse lockout in this picture;
The 4+1 was not an overdrive transmission,but they had a low 1st gear and a 1:1 fifth gear,here are the ratios in the street 5-speed: 1st-3.27, 2nd-2.14, 3rd-1.57, 4th-1.23, 5th-1:1
These ratios were ideal for rear gearing of 3.08:1 or taller gears.
While not an overdrive,the low 1st gear along with the now 3.00:1 in the Ford 9 inch gives me a 9.8:1 starting line ratio,(3.27 X 3.00).This gives the Monte a good bottom end punch in 1st gear and I'm cruising on the highway with the 3.0:1 rear gearing.
Over the years the Doug Nash has been apart several times for repairs such as a third gear that broke at the strip one time,synchro keys,synchro rings,etc.
Rick Roods Transmission has done all the work on this tranny since I have had the Monte;
http://www.rickroodstransmission.com/home.htm
A few years ago I found a 2 part video on this transmission made by Paul "5speed" Cangialosi where he goes into detail on how to "Blueprint" the 4+1 for better shifting and longevity.Here are the links;
https://www.youtube.com/watch?v=6UnFDaAdBaM
https://www.youtube.com/watch?v=UQMmXd0e91U
I asked Rick to watch these videos and use all the little tips that Paul showed in them.I then had the trans rebuilt,but before re-assemble I sent some of the gears and both shafts to Industrial Cryogenics Enterprises LTD in St Catherines Ontario Canada;
https://www.ctidirectory.com/search/company.cfm?company=49718
Here is a picture of the parts I had treated;
From the research I did the Cryogenic treatment is supposed to increase the strength of the treated parts by approximately 30 %.And they seem to be holding up fine so far and that has been over four years ago now.
I had shifting issues back in 2015 and with the help of the Speed Talk Forum,especially Ray "Side Step' Spediacci I got it straightened out.
Then it started getting hard to shift again in late 2019,but I drove it like that for the remainder of the season.
This brings me to June/July of 2020 when I tackled this issue again.
The first thing I found was the Clutch Z Bar,or bell crank,was worn and the holes were egged out.
I fixed that with the help of Jim George at Scotia Machine Shop in Kentville NS.He made a new clutch fork pushrod with a Heim joint where it goes to the Bell Crank.Then he mad a bushing for the other end where the clutch fork pushrod goes.This made a big difference in reducing the excess play in the clutch linkage.Here are a couple of pictures;
That worked fine until the bracket that goes from the clutch pedal pushrod to the bell crank broke at the weld.Mark Broome helped me with this by welding the bracket back in place.
Then it started to get hard to shift again,so I pulled the trans,bellhousing,clutch and flywheel off for a closer look.
Turned out there were a couple of more issues.The throwout bearing was broken where it rides on the clutch fork.The clutch fork was worn where the TOB rides on it.The clutch fork pivot ball was bent and loose from the threads being mostly stripped.And the bolt holes in the bell where the trans bolts had some threads missing.The holes in the frame that the bell crank bracket bolt to were also mostly stripped.
I was able to fix this by drilling the holes to 1/2 inch and then I took some 3/8 nuts,rounded the corners off a little bit,then I pounded them into the holes.I plan to see if Mark will tack weld them for me to make sure they dont come out.
But,on the bright side,the clutch and flywheel still looked fine.
I already had a new Hayes # 70-101 TOB.Rick Rood welded up the clutch fork and ordered me a new Lakewood adjustable pivot ball,# 15501 and some Royal Purple 75W-90 synthetic gear lube.
Jim George helicoiled the stripped bolt holes in the bellhousing for me.
I also wanted to replace the Allstar Extended Length pilot bearing with a Allstar extended length bronze bushing while I was at it.The old pilot bearing came out with the aid of a hammer and cold chisel and I measured the ID of the crank snout with a telescoping Tee gauge.I took my Tee gauge and the new pilot bushing out to Jim George and he measured it and found that it was 0.010 too big,so he turned it down for me.
Before I put the new pivot ball in I watched this video on Team Chevelle posted by Al "Dutch Max Headwork";
https://www.chevelles.com/forums/33-transmission-driveline/1100202-clutch-pivot-ball-height-check.html
I measured the flywheel deck height of the GM flywheel,which was very close to the measuremants in the video,and I set the pivot ball to the recommended height of 4.750 to the engine side of the bellhousing.Here is a picture of that procedure;
I started to re-assemble everything and it went smoothly until I got to the shifter.When I took it out I had inadvertently removed one of the mounting bolts without thinking.As I picked it up all the pieces fell out of place,gates,bushings and shims.It took me quite a while to figure out how it all went back together.
Anyhow,I got it all back together and now it is shifting smoothly again.Until next time anyhow,LOL
Here a few more pictures;
Subscribe to:
Posts (Atom)